The Cohost Global Feed on Hill's Space

WHOOOAAAAAAA COOOOOOL

hillexed@email.com (hillexed) — Mon, 08 Apr 2024 20:42:38 +0000

More photos to come after I get em off ghe phone in hd

8" Parabolizing attempt #2: Abort...

hillexed@email.com (hillexed) — Sun, 17 Mar 2024 18:05:44 +0000

My local astronomy club has a foucalt tester, and today I tested that mirror after 30 seconds of parabolizing. It revealed a big turned down edge (yahoo…) and some slight zones in the center of the mirror. I knew those zones existed - heck, you can even see the slight non-sphericalness in the second image of my “close enough to spherical!” celebration - but the radius of curvature changes rapidly where one zone meets another instead of smoothly blending. I was willing to call that close enough, but according to my local astronomy club’s resident professional optician, that non-smooth curvature would throw light all over the place and was bad enough I should return to a sphere and smooth that out. AAAAARGH

For reference, a mirror is usually considered good enough if its shape is within 1/4 of a wavelength of light (usually green light, wavelength 500 nanometers) - of an idealized parabola. This optician is a perfectionist thinks there’s no reason an amateur telescope mirror can’t get to within 1/10 of a wavelength. I appreciate his optimism but man I don’t want to return to sphere a second time.

…I’m going to return to sphere a second time. I saw the zones using my current testing setup - I just ignored them. This is possible. I can do this.

Total grinding time: 26 hours

8" Parabolizing attempt #2: Abort...

hillexed@email.com (hillexed) — Sun, 17 Mar 2024 18:05:44 +0000

Unable to find image 512image2.png

Unable to find image 512image.png

…I’m going to return to sphere a second time. I saw the zones using my current testing setup - I just ignored them. This is possible. I can do this.

Total grinding time: 26 hours

8" Mirror Parabolizing: Oh No Not Again

hillexed@email.com (hillexed) — Sat, 16 Mar 2024 14:38:47 +0000

I’m parabolizing my telescope mirror - I’ve ground it to a sphere shape, and now I’m grinding a tiny bit more to change its shape precisely into a parabola.

I’ve done 3 grinding sessions for a total of 34 minutes of grinding. Here’s a Ronchi picture of my current progress. Mel’s online Ronchi calculator has overlaid some semi-transparent white lines which show the ideal Ronchi grid of a somewhat parabolized mirror. Looks like the center is fine, but the edge is focusing light too close - similar to what happened in parabolizing attempt #1. I’ll need to think to figure out how to solve this.

8" Mirror Parabolizing: Oh No Not Again

hillexed@email.com (hillexed) — Sat, 16 Mar 2024 14:38:47 +0000

Unable to find image image.png

Unable to find image texereau-normal

I’m parabolizing my telescope mirror - I’ve ground it to a sphere shape, and now I’m grinding a tiny bit more to change its shape precisely into a parabola.

8" Mirror grinding: Parabolization #1

hillexed@email.com (hillexed) — Sat, 16 Mar 2024 00:43:46 +0000

I’m in the home stretch - my goal is to turn this sphere shaped mirror into a parabola shaped mirror.

The final stage of mirror grinding is called either parabolizing, because you’re making a parabola, or figuring, because you have to measure carefully and that involves numbers which are also called figures. You use a stroke that goes up and down fast and side to side slowly in a big zigzag, called a W stroke, to remove a tiny bit of glass from both the center and the edge, as seen in the first picture (from Mel Bartels’ site).

This stage involves removing very small amounts of glass, so parabolizing is very quick. After 15 minutes of a W stroke - which is crazy fast compared to hours and hours it took to get to spherical - my center was slightly deepened, enough to match a parabola! My mirror edge, however, still had very straight bands. The Ronchi test calculator said my edge wasn’t where it should be.

Then I made a mistake: the amateur astronomers in the discord said I had a turned edge, and I needed to return to spherical. A mirror edge that’s too low can only be fixed by grinding the rest of the rest of the mirror down to that height. So I spent anouther two hours undoing all my hard parabolizing work.

But in retrospect, I didn’t need to do that at all - my edge was focusing light too close, so if I wore down the edge it would have focused light at a longer radius of curvature, which is what I wanted! I could have done that! I mistook the error for “turned down edge” when actually the edge wasn’t turned down enough!

Anyway, I’m back at a sphere. Parabolization attempt #2: begin!

8" Mirror grinding: Parabolization #1

hillexed@email.com (hillexed) — Sat, 16 Mar 2024 00:43:46 +0000

Unable to find image parabolastrats.png

Unable to find image 510400-1.png

Unable to find image 510400-2.png

I’m in the home stretch - my goal is to turn this sphere shaped mirror into a parabola shaped mirror.

Anyway, I’m back at a sphere. Parabolization attempt #2: begin!

8" mirror grinding: SPHERICAL ENOUGH TO CELEBRATE

hillexed@email.com (hillexed) — Sun, 10 Mar 2024 18:11:13 +0000

This site is my secret weapon: https://www.bbastrodesigns.com/ronchi.html

It’s a slightly janky javascript app made by some old telescope maker in Oregon, and it lets you get quantitative measurements from all those Ronchi pictures. Very important.

Looks like my outer zone focuses light at around 0.066 in from my desired radius of curvature, and inner zone focuses light at around 0.1 in. (There’s probably big error bars on both those numbers). Only the relative number of “inner zone focuses 0.1-0.66in = 0.03 in closer than outer zone” really matters.

Since the focal length is half the radius of convergence, that means my mirror focuses space light to 0.015" of where a spherical mirror would. Not bad!

CLOSE ENOUGH! SPHERE-ISH ACHIEVED!!

But my goal is to focus space light. A sphere will bounce light from center point back to itself, but to focus parallel light rays from space to a single point, I need a parabola.

Jean Texereau’s book says the formula for “parabolic abberation”, how different a parabola is from a sphere, is that the zone with radius h from the mirror should focus a distance Δp = h^2 / R further from the radius of curvature. Tape measure and eyeball says as I move my tester backwards, the ronchi switches from bands get wider to bands get smaller at 89 + 1/16", so that’s the radius of curvature of my mirror (which is twice the focal length). By that formula, my goal is to have the very edge focus h^2/R = (1*8/2)^2/89 + 1/16" = 0.1796" further from the front.

Above I calculated that the edge focuses 0.03in closer than the front. Wow, I went so far past parabolic in my quest to get to spherical. I think I’m ready to parabolize.

To parabolize, I have to deepen this curve around six times its current amount. That’s doable! The open astronomy discord recommended I start by smoothing out the division between the two zones with long strokes, and then begin using a different stroke to deepen the center. Let’s do this

Total grinding time: 21 hours

8" mirror grinding: SPHERICAL ENOUGH TO CELEBRATE

hillexed@email.com (hillexed) — Sun, 10 Mar 2024 18:11:13 +0000

Unable to find image 4995398-pic-1.png

Unable to find image 4995398-pic-2.png

Unable to find image texereauabberation.png

This site is my secret weapon: https://www.bbastrodesigns.com/ronchi.html

It’s a slightly janky javascript app made by some old telescope maker in Oregon, and it lets you get quantitative measurements from all those Ronchi pictures. Very important.

Since the focal length is half the radius of convergence, that means my mirror focuses space light to 0.015" of where a spherical mirror would. Not bad!

CLOSE ENOUGH! SPHERE-ISH ACHIEVED!!

But my goal is to focus space light. A sphere will bounce light from center point back to itself, but to focus parallel light rays from space to a single point, I need a parabola.

Above I calculated that the edge focuses 0.03in closer than the front. Wow, I went so far past parabolic in my quest to get to spherical. I think I’m ready to parabolize.

Total grinding time: 21 hours

8" Mirror Grinding Update: ALMOST THERE

hillexed@email.com (hillexed) — Sat, 09 Mar 2024 21:30:19 +0000

I’M SO CLOSE TO A SPHERE

(You know you’re a sphere when the lines are completely straight. See this infographic for more)

total mirror grinding time: TWENTY GODDAMN HOURS

8" Mirror Grinding Update: ALMOST THERE

hillexed@email.com (hillexed) — Sat, 09 Mar 2024 21:30:19 +0000

Unable to find image IMG_20240309_162343854~2.jpg

Unable to find image IMG_20240309_162149283~2.jpg

Unable to find image IMG_20240309_161749437~2.jpg

I’M SO CLOSE TO A SPHERE

(You know you’re a sphere when the lines are completely straight. See this infographic for more)

total mirror grinding time: TWENTY GODDAMN HOURS

8" Mirror grinding: Flower Power

hillexed@email.com (hillexed) — Wed, 06 Mar 2024 21:33:57 +0000

I’m using an advanced technique: cutting out pieces of paper and putting them under the tool while pressing to avoid certain areas of the tool touching the mirror. I know I have a hole in the middle, so by blocking the middle from wearing down I can concentrate my wearing on the outer zones without making the center even deeper.

Looks like after a few hours I’ve managed to get the outer zone almost completely spherical! There’s a bit of TDE left to fight and the center is a bit messed up but I think I’m very close.

From here I could either get everything to a sphere and grind out that TDE and then wear down the center again to make a parabola, or see if I can go to a parabola from where I am now. I don’t quite know how to decide.

8" Mirror grinding: Flower Power

hillexed@email.com (hillexed) — Wed, 06 Mar 2024 21:33:57 +0000

Unable to find image IMG_20240306_124746726_1.jpg

Unable to find image IMG_20240306_160753289~2.jpg

Unable to find image IMG_20240306_160449695~2.jpg

Looks like after a few hours I’ve managed to get the outer zone almost completely spherical! There’s a bit of TDE left to fight and the center is a bit messed up but I think I’m very close.

A Ronchi Test Infographic: How to read my funny red stripe pictures

hillexed@email.com (hillexed) — Mon, 04 Mar 2024 23:05:04 +0000

Check out this infographic of how to read the Ronchi tests of my telescope mirror! I’ve been posting lots of pictures like this as I grind, and this tells you how to interpret what the pictures say about a mirror’s shape. The Ronchi test can be used to roughly measure a mirror’s shape and see any turned down edge (“TDE”), and with a computer program to analyze them, even give some quantitative measurements.

(I drew the light hitting the mirrors on the left as parallel lines for clarity, but in the ronchi test the light is actually coming from a single point close to the focus. don’t tell anyone)

A Ronchi Test Infographic: How to read my funny red stripe pictures

hillexed@email.com (hillexed) — Mon, 04 Mar 2024 23:05:04 +0000

Unable to find image ronchi_infographic.png

Unable to find image 4890338-a-ronchi-test-infogr-image.png

(I drew the light hitting the mirrors on the left as parallel lines for clarity, but in the ronchi test the light is actually coming from a single point close to the focus. don’t tell anyone)

The Art Of Figuring

hillexed@email.com (hillexed) — Thu, 08 Feb 2024 18:00:57 +0000

This pretty art piece is actually a precise measurement of my progress in telescope mirror grinding. It looked fun enough out of context I decided to post it!

You’re looking at multiple overlaid square images. Each one is a Ronchi test, which tells me the shape of my mirror on a nanometer scale in the shape of the red stripes. As I polish the mirror, it changes shape, so after 20 minutes of polishing I want to measure the new shape. Each time I test, I precisely align my handheld tester, and then take a photo with my phone. Since the tester is in a different place at a time, I have to place my phone on its corner and lean it to one side to put the camera at the right height - but that rotates the image, so afterwards I load up the Ronchi test images in Krita and de-rotate them so the stripes go up and down, so I can compare the images as I grind. You’re looking at a Krita file with many Ronchi images, each rotated and scaled so the mirror is the same size and in the same place. It makes a nice flower shape!

The Art Of Figuring

hillexed@email.com (hillexed) — Thu, 08 Feb 2024 18:00:57 +0000

Unable to find image ronchiart.png

This pretty art piece is actually a precise measurement of my progress in telescope mirror grinding. It looked fun enough out of context I decided to post it!

8" mirror Polishing, part 4: Seeing by Standing on the Shoulders of Plastic

hillexed@email.com (hillexed) — Fri, 02 Feb 2024 18:12:05 +0000

To test the shape of a mirror, amateur telescope makers have a few tests which involve bouncing light off the mirror to see its shape. One cheap one is the Ronchi test, which sends light through a grating of fine lines, bounces off the mirror, and then you place the grating at the radius of convergence of your mirror so it blocks part of the light and reveals the mirror shape. Nowadays you can make a grating by using a high DPI laser printer! I didn’t have one but someone in the Observational Astronomy discord named chantepierre did, so he mailed me a Ronchi grating in an envelope from France two months ago. Thank you, chantepierre!

I set up a Ronchi tester using a 3D printed part, LED, resistor, and battery - I just taped the Ronchi grating to the front. But I couldn’t see anything when I looked, because the mirror was tilted wrong. So I printed a mirror stand! The mirror stand sort of helped, but the print warped, so it wasn’t as helpful. Finally I realized I needed my tester to be higher, so once tester v2 stood proudly on tester v1, I was able to see the LED’s reflection through the grating and take a photo!

These stripes tell me… that a fridge nearby is vibrating. Sigh. But at least I’m seeing stripes!

Total polishing time so far: 70 minutes

8" mirror Polishing, part 4: Seeing by Standing on the Shoulders of Plastic

hillexed@email.com (hillexed) — Fri, 02 Feb 2024 18:12:05 +0000

Unable to find image IMG_20240126_215335157_1.jpg

Unable to find image IMG_20240127_110757751.jpg

Unable to find image IMG_20240130_005945275_1.jpg

Unable to find image IMG_20240130_004837861.jpg

These stripes tell me… that a fridge nearby is vibrating. Sigh. But at least I’m seeing stripes!

Total polishing time so far: 70 minutes

Meniscus mirror mold, attempt #2

hillexed@email.com (hillexed) — Wed, 31 Jan 2024 22:34:45 +0000

To give a circle of glass (approximately) the right curve for a telescope mirro,, I want to make a precisely shaped mold that can withstand kiln temperatures. This technique makes what’s called a meniscus mirror.

Last time I tried this, the wood delaminated and came apart at the boundary where one plank was glued to another. This time, I’m spraying the wood with polyurethane spray on both the front AND back side, to avoid any warping before I put the furnace cement in. It seems to have warped a tiny bit, but only a fraction of an inch off the ground at one end. Hopefully it’ll be OK.

Printed a new trowel (I love that I can say that), sanded the wood, wiped off dust with alcohol soaked paper towel, bought a different type of furnace cement, and spread furnace cement. Hopefully this will give me a nice curved furnace cement mold!

Meniscus mirror mold, attempt #2

hillexed@email.com (hillexed) — Wed, 31 Jan 2024 22:34:45 +0000

Unable to find image IMG_20240131_170731472_1.jpg

Unable to find image IMG_20240131_172405688_1.jpg

8" Mirror Polishing, Part 3: First Strokes

hillexed@email.com (hillexed) — Tue, 30 Jan 2024 17:11:15 +0000

After all that setup, actually polishing a mirror is surprisingly simple. First you put your mirror on your tool and apply pressure so the pitch flows and takes the shape of your mirror (which happens faster if it’s hot, so you can leave the pitch lap in hot water to heat it up and speed up pressing). Then you take your mirror, put it on your tool, and push it back and forth without applying any downwards pressure. Pressure is an advanced technique that makes the polishing go faster, but too much pressure can grind one part of a mirror slightly lower.

After a few minutes every time I rotated the mirror there was a ringing squeak noise like dragging your finger along the rim of a wine glass. Allegedly that’s a good thing, but it makes me nervous when I hear it.

It turns out grinding a mirror involves grinding. My arms got tired after 30 minutes. Well well well, if it isn’t the consequences of my own actions.

8" Mirror Polishing, Part 3: First Strokes

hillexed@email.com (hillexed) — Tue, 30 Jan 2024 17:11:15 +0000

Unable to find image IMG_20240127_141903995_1_1.jpg

Unable to find image IMG_20240127_153114171_HDR_1.jpg

It turns out grinding a mirror involves grinding. My arms got tired after 30 minutes. Well well well, if it isn’t the consequences of my own actions.

8" Mirror Polishing, Part 2: Curveball Pitch

hillexed@email.com (hillexed) — Fri, 26 Jan 2024 17:16:15 +0000

I’m making a tool called a pitch lap to grind an 8" mirror. Previously, I discovered the best way to find dental stone is a dentist, and made a yellow plaster disk.

Pitch lap step 2: Pour the pitch!

Pitch is a weird material. It’s a liquid so viscous it looks like a solid. At high temperature it’ll pour like honey, at low temperature it’ll act solid but very very slowly flow. When grinding a mirror, we use pitch so it’ll keep flowing by a few nanometers and keep touching and grinding the mirror even as the mirror’s shape changes.

Hot pitch sticks to anything. Cold pitch cracks and sprays tiny dust crumbs everywhere. It’s annoying to work with. I bought a sacrificial pan from goodwill for $5 to hold the pitch, and I’m glad I did because that pan is never getting the pitch out.

The individual steps themselves were pretty simple: first heat up the pitch (this took hours to heat it evenly up to 150F), then pour it on top of your tool, then press the mirror onto your pitch so the top surface becomes shaped like your mirror.

Before that I had to cut away the edges of my dental stone tool with a razor blade, which I’d never done before and my slowness made the local astronomy club impatient.

The very very final step is to cut lines into the plaster so it can flow easier. Normally this is done right after pouring… but I had to leave for something time sensitive, and that meant the 99% complete pitch lap sat in a box for a month.

A month later, I cut some channels using a razor blade (the others made it look so easy!), warmed up the pitch by putting it in warm water, and then pressed the mirror face onto it. A bag of onions helped create tiny channels called “microfacets” so the pitch can flow easier.

Pitch lap complete! All I need is some cerium oxide polishing agent and a way to test my mirror, and I’m ready to start polishing.

8" Mirror Polishing, Part 2: Curveball Pitch

hillexed@email.com (hillexed) — Fri, 26 Jan 2024 17:16:15 +0000

Unable to find image IMG_20231216_141319656_HDR_1.jpg

Unable to find image image.png

I’m making a tool called a pitch lap to grind an 8" mirror. Previously, I discovered the best way to find dental stone is a dentist, and made a yellow plaster disk.

Pitch lap step 2: Pour the pitch!

Before that I had to cut away the edges of my dental stone tool with a razor blade, which I’d never done before and my slowness made the local astronomy club impatient.

Pitch lap complete! All I need is some cerium oxide polishing agent and a way to test my mirror, and I’m ready to start polishing.

8" Mirror Polishing, Part 1: The Power of Teeth

hillexed@email.com (hillexed) — Fri, 26 Jan 2024 05:20:59 +0000

Previously, @Beasmeeply generously donated me an 8" mirror blank, kick-starting an attempt to finish grinding it and make an 8" telescope. There are four stages of mirror grinding, so to figure out which step I needed to start with, I put the mirror into a Foucault mirror tester, and it gave a smooth-ish image, telling me BeasMeeply had gotten through the first two stages of mirror making, rough and fine grinding, and it was ready to polish.

The next step is polishing, and to do that, I need a pitch lap! A pitch lap is a disk the same size as a mirror with a layer of pitch poured onto it and used as a grinding surface.

Step 1: Make a disk.

Nowadays the cheapest way to do it is with waterproof plaster called dental stone. A local astronomy club had some and was willing to mix up some so I could use it… but they only had a paper bowl to mix it up in, we used too little, and the result was a thin pancake that cracked easily. I needed more stone and a thicker tool.

I looked online for where to buy dental stone. Assuming you don’t want to buy a 25 lb bulk box ( I only need 1lb), it’s very hard to find anywhere but the slightly expensive firsthanddiscovery.com .

And then: by chance, I had a pre-scheduled dentist appointment. During the appointment, I asked nicely, and they sent me home with two ziplock bags full of dental stone!

A trip to Goodwill got me a big plastic jug for mixing lots of dental stone in, and which I was okay ruining with bits of hardened stone. (The flexible plastic walls ended up being convenient for cleanup later - bending them meant large bits of hardened-on plaster cracked off!)

I got help online with the water-to-powder ratio 30 ml water/100 g powder, grabbed one of my failed wooden carvings from the meniscus mirror project to contain any spills, and got mixing. Dental stone hardened so quickly - within two minutes it was noticably hard to mix. I thought I had messed up the water-to-powder ratio because it felt too dry, so I added more water and then it was suddenly very runny. When I dipped a plastic fork in it, it didn’t drip off the fork, however.

Worried that if I waited any longer it would harden, I poured the plaster (using my mirror blank as the mold with a layer of plastic wrap on top). The dental stone was already so viscous it didn’t smooth itself out to a level surface, giving me an uneven back.

Then I had to wait a week for it to dry before I could turn the stone disk into a proper grinding tool!

8" Mirror Polishing, Part 1: The Power of Teeth

hillexed@email.com (hillexed) — Fri, 26 Jan 2024 05:20:59 +0000

Unable to find image IMG_20231202_150448568_HDR_1.jpg

Unable to find image IMG_20231207_160216875_1.jpg

Unable to find image IMG_20231207_162328078_1.jpg

Unable to find image IMG_20231207_170016712_1.jpg

The next step is polishing, and to do that, I need a pitch lap! A pitch lap is a disk the same size as a mirror with a layer of pitch poured onto it and used as a grinding surface.

Step 1: Make a disk.

And then: by chance, I had a pre-scheduled dentist appointment. During the appointment, I asked nicely, and they sent me home with two ziplock bags full of dental stone!

Then I had to wait a week for it to dry before I could turn the stone disk into a proper grinding tool!

The galaxies are aligned!!

hillexed@email.com (hillexed) — Tue, 02 Jan 2024 00:11:06 +0000

This is the best photo I’ve made of the Andromeda galaxy!

It’s my second time stacking pictures to bring out faint details. You’re looking at 20 phone pics taken through my 3D printed telescope, each 1/2s exposure so the Earth didn’t rotate as much during the photo and smear the stars. I tried the program deepskystacker, but it failed to stack my pictures (maybe my phone camera’s pics had too much noise?) so over 3 days I wrote some custom python code using astropy and astroalign to stack them myself!

Look at all those dim stars! That’s so many stars! In the bottom right that slightly fuzzy star is actually the core of M31’s satellite galaxy M110! I was hoping to see some dust lines or spiral arms, but I guess I’ll need more data for that.

My first Orion nebula!

hillexed@email.com (hillexed) — Sat, 11 Nov 2023 04:00:21 +0000

The first picture is at 36x zoom, the second one at 150x zoom. The more zoomed in one is fainter because the same light is spread across more area, but you can see the four trapezium stars as four separate streaks!

This was a very frustrating night for photography because finding things in a big sky is hard. Light pollution made it hard to see M31, I couldn’t find M33, and then finally clouds rolled in and it became a race against time to photograph the Orion nebula M42. I really need a motorized mount or other device to help me find things.

A friendly older guy helped me use his shopbot

hillexed@email.com (hillexed) — Tue, 24 Oct 2023 17:57:56 +0000

I’m so excited. Making really big really thin meniscus mirrors has officially gone from cool idea to possible

A friendly older guy helped me use his shopbot

hillexed@email.com (hillexed) — Tue, 24 Oct 2023 17:57:56 +0000

Unable to find image IMG_20231024_132057346_HDR_1.jpg

Unable to find image IMG_20231024_134541085_HDR_1.jpg

I’m so excited. Making really big really thin meniscus mirrors has officially gone from cool idea to possible

Adjusting for mirror size

hillexed@email.com (hillexed) — Mon, 23 Oct 2023 14:55:28 +0000

I got a mirror that’s 2.3 inches wide. However, several weeks ago, I printed a mirror holder that was designed to fit a mirror 2.46 inches wide. Sure, I could just use the bigger holder, but the bigger the secondary holder the more light it blocks from reaching your mirror. Is it worth a smaller secondary mirror holder that will block half a square inch less light? Yes, I decided. So I opened up the model and slightly scaled it down. It was a bit tricky because I didn’t want to scale down the nut and screw holes, but I counted the sizes and scaled down the outside vertices in blender. I feel bad about wasting my previous print, but plastic is so cheap I’ll only feel a little bad about it.

Secondary mirror get!

hillexed@email.com (hillexed) — Thu, 19 Oct 2023 20:19:03 +0000

Visiting family in another city, and turns out there’s an astronomy store named La Maison De L’Astronomie (The Astronomy House)! I called them up to see if they had some secondary mirrors in stock… And they did! They had so many big telescopes, way more small refractors than I was expecting, a huge cabinet of binoculars, and some absolutely massive tripod mounts.

The bbastro calculator says the most optimal uniform illumination secondary mirror size is 62.5mm, which is $60 online (before tax and shipping!) but anything above 50mm will be better the bigger you go. I got this 58mm from them for $40 after tax and I am the shipping. An absolute steal. Just like the space shuttle and canadarm, my 8" Leavitt telescope will be mostly American with one vital Canadian part.

M13, the great hercules cluster

hillexed@email.com (hillexed) — Wed, 18 Oct 2023 14:08:06 +0000

I found this with the help of an amateur with a huge telescope and laser pointer so bright it looked like a line pointing into the sky. Looked like a dim circular smudge to the eye. Picture taken with the 25mm eyepiece, so I bet I could get an even better picture through the more zoomed in 6mm

Annular eclipse today!

hillexed@email.com (hillexed) — Sat, 14 Oct 2023 14:21:02 +0000

Reminder to North and South Americans, there’s an eclipse today! https://www.timeanddate.com/eclipse/in/usa?iso=20231014 DON’T LOOK AT THE SUN WITHOUT SPECIAL ECLIPSE GLASSES, EVEN DURING A PARTIAL ECLIPSE! If you don’t have one, take a piece of paper, punch a hole in it, and look at the shadow. Trees or colanders with many holes will make very cool shadows!

hillexed@email.com (hillexed) — Fri, 13 Oct 2023 17:14:11 +0000

I was cleaning out my boxes when I discovered @Beasmeeply not only sent me a primary mirror, but also a 46mm secondary mirror! Wow! Thank you!

Secondary mirror sizes are weird; apparently having a secondary mirror too small means the outer part of your view is slightly dimmer. I did lots of research into what kind of secondary mirror to use. This calculator says a 62.5mm will give me the most even illumination across the field, but that’s for super huge eyepieces so a slightly smaller one should be fine. I’d love to find a 60mm or 55mm one but I guess now I don’t have to look nearly as hard

I GOT THE RING NEBULA

hillexed@email.com (hillexed) — Wed, 11 Oct 2023 15:22:43 +0000

YEAHHHHH FINALLY

IT’S SO SMALL

FINDERSCOPE HELPED

hillexed@email.com (hillexed) — Wed, 11 Oct 2023 14:30:55 +0000

Got this used finderscope from the local astro club, designed and printed a mount for it. Took two revisions

Telescope update:

hillexed@email.com (hillexed) — Mon, 09 Oct 2023 18:13:12 +0000

I put a telescope on my telescope

I tested my donated mirror

hillexed@email.com (hillexed) — Sun, 08 Oct 2023 15:06:35 +0000

WOW! That’s a good mirror!

Previously, @BeasMeeply graciously donated me an 8" mirror. The problem: I don’t know what stage of mirror making I have to do.

So I talked to a local astronomy club. I got to use a spherometer to measure the curve - same curvature all around, accurate to within 0.0002 inches. I put it in a foucalt tester, and after lots of help and fiddling I got some pictures of the result! The fact that it’s transparent enough that I can see through the glass and get a result in the foucalt test tells me @BeasMeeply got through grinding and polishing, and now I can skip to making a pitch lap.

How do I interpret this? I don’t know yet. But someday I will

I tested my donated mirror

hillexed@email.com (hillexed) — Sun, 08 Oct 2023 15:06:35 +0000

Unable to find image IMG_20231007_152202849_smol.png

WOW! That’s a good mirror!

Previously, @BeasMeeply graciously donated me an 8" mirror. The problem: I don’t know what stage of mirror making I have to do.

How do I interpret this? I don’t know yet. But someday I will

Printing for the 8\" telescope has begun

hillexed@email.com (hillexed) — Sun, 01 Oct 2023 20:51:59 +0000

I’m not the first person to build a Hadley 3D printed telescope and then want something bigger. There are two 3D printed 8" telescope designs: the “Bradley” is only available by DMing someone on a discord server, and it’s designed for a printer big enough to fit an 8" circle. I don’t have a printer that big! Thankfully, there’s also the “Leavitt”, a design which splits 8" circles into three pieces so they can fit on a normal Ender-sized printer.

I’ve begun printing all the pieces! It’s a lot of printing; at least 100 print hours. I bought one roll of blue and one roll of black filament. In a telescope, you want to make inside surfaces black so they don’t reflect stray light and brighten the view. The tube parts are so tall and thick, and there’s so many near the path of light, that I used up all my black filament halfway through all the tube sections. I’ll need to print the rest in blue but spray paint them black.

Interestingly, there’s also a remix called the Leavitt Lite which edits the Leavitt to use metric screws/bolts and makes many parts thinner and lighter. One interesting change the Lite made is using a bigger secondary mirror than the original for better illumination; I’ve downloaded the file from the Leavitt Lite and edited it to use #10 nuts so I can use that change too. Now I need to find or buy a 62.5mm secondary mirror.

One other thing to think about: metal rods. I have three 36in thin-walled rods in my wobbly first mount. I could reuse those for my Leavitt for free. My donated mirror’s focal length is 43in right now, meaning I’d need to place the eyepiece 43in away from the mirror, and that won’t fit on those 36in rods.

One option is I could grind the mirror and reduce the focal length to 36in, giving me an 8" f/4.5 mirror, and then use my existing rods. Same focal length means same magnification… but I like the idea of having a longer focal length and therefore more magnification than my previous telescope. Another option: I could either leave the focal length alone (or increase it), but then I’d need to buy 3 new longer 1/2" tubes for an extra $40 or so.

Paint, rods, and secondary mirrors. Many things to think about.

Printing for the 8\" telescope has begun

hillexed@email.com (hillexed) — Sun, 01 Oct 2023 20:51:59 +0000

Paint, rods, and secondary mirrors. Many things to think about.

An incredibly generous donation

hillexed@email.com (hillexed) — Thu, 28 Sep 2023 15:12:15 +0000

A while ago I was musing about ways to get better space pics, and @BeasMeeply incredibly generously offered to donate an 8" blank sitting in his closet for 10 years if I paid for shipping! Thank you so much! I’ve got it now and it looks incredibly clear. He also sent a metal 1.25" focuser, which was an extra addition I wasn’t expecting.

It’s like I was standing on the edge of an abyss deciding whether not to jump in, and then someone threw a mirror at my back. I guess I’m falling in! Now I need to figure out how to measure its curvature, polish it using a pitch lap, and then aluminize it. It’s a lot of work… but it’ll be worth it. I’m excited!

An incredibly generous donation

hillexed@email.com (hillexed) — Thu, 28 Sep 2023 15:12:15 +0000

Unable to find image IMG_20230919_223643192_1.jpg

hillexed@email.com (hillexed) — Mon, 25 Sep 2023 04:59:14 +0000

I took out a relative’s 8x42 binoculars today. Saw M7 as a faint sparkling of stars, but Andromeda was a much dimmer smudge compared to my telescope that if I hadn’t seen it before I wouldn’t have been able to spot. It I was able to follow a satellite though! And I got to show off Mizar and Alcor to others!

Sadly the moon was out and it was so bright it was casting shadows, stopping me from seeing any nebulae like I was hoping. Grr, how dare the moon be out there.

ANDROMEDA GALAXY CORE

hillexed@email.com (hillexed) — Wed, 20 Sep 2023 14:36:37 +0000

I got to see it with my own eyes for the first time!! It looked like a gray oval-ish but slightly pointy smudge. But it’s a cool smudge in the sky!!

This is a phone pic with a 2s exposure and ISO cranked up to it’s max, 3200. The rainbow snow is random noise from my sensor magnified by turning the sensitivity up very high. You can even see M32 as a slightly fuzzy star almost directly above Andromeda’s core!

I’m really glad I found it. Aiming the telescope was annoying, but rubber bands on the mount helped it keep its aim. I guess that means when I tried and failed to find the ring nebula, it’s just too faint to see in my light polluted sky.

I took many 1s exposures, too. I need to figure out how to stack them and use astronomy software but that’s a process for another time

Dumb telescope idea: liquid mirrors

hillexed@email.com (hillexed) — Mon, 18 Sep 2023 17:27:56 +0000

I’ve been thinking about https://www.space.com/liquid-telescope-construction-in-space-ax-1 . I wonder if you could take a circular baking tray, spin it on a pottery wheel, and then pour SLA 3D printing resin into it so the resin would form a liquid mirror, then shine UV light on it to cure it and make a telescope mirror

oh yeah, I'm making a pifinder

hillexed@email.com (hillexed) — Sun, 10 Sep 2023 01:01:27 +0000

The sky is too big. I went out telescoping looking for M13 and there were too many stars and it’s too big and I don’t know where I’m aimed. When you’re so zoomed in, there’s so many stars you don’t know where you are or where to look.

Enter the pifinder! I’m going to make one.

I went to my local makerspace, known for having too many donated bits and bobs they actively try to get rid of (what a wonderful problem to have). I found an old project involving a pi, a decade old pi camera v1, and a battery pack that I was allowed to take and cannibalize on the condition that I show off the final product. Thank you!

Pifinders are normally sold for $600 fully assembled because that’s what similar units cost, because the astronomy market is nuts. The creator sells cheaper DIY kits, thankfully. I’ll be able to save even more DIYing because unlike a normal pifinder, my janky secondhand pifinder will have:

A different battery No GPS module (those are $50!!!), instead I’ll mod the code to input my GPS coordinates from the GPS in my phone A slightly different IMU chip A much smaller and older camera, compared to the $50 raspberry pi HD camera twice the size with a convenient screw-on lens interface

Surely none of this will hassle me and I can save money without any consequences!

Progress so far

First, I needed to buy a lens for my camera!

Looking at what’s written on the ribbon cable of the camera, I have a pi camera v1. According to https://www.raspberrypi.com/documentation/accessories/camera.html the sensor is 3.76 × 2.74 mm big, so I can use FoV = 2 * math.atan((2.74/2)/22) * 180/math.pi

Turns out lenses are tricky. The official pifinder uses a 25mm lens. Why? It uses the “tetra3” library by the European Space Agency to go from pictures of stars to figure out where in space you are. You also need to pass in the FoV of the image. Pifinder expects a 10.2 degree FoV, and it has a database that works with FoVs from 10 to 20 degrees. I looked up the formula, and my smaller camera’s smaller sensor size would give me a TINY FoV with the same 25mm lens. Oops! I ended up buying a 12mm lens for a 13deg focal length.

Next, getting it on the board. I lost one of two screws holding it on. Following this video, I printed a M12 lens adapter, which had screw holes too small but otherwise fit perfectly. However, I also needed to remove the existing lens. There are printed tools for that, but many are a + shape for the pi camera v2, and the pi camera v1’s lens is a different shape with 3 spokes. Eventually I found one, printed it, unscrewed it, finished the job with pliers, and put on the lens. It does seem more zoomed!

Configuring the raspberry pi was a bit annoying. Running “libcamera-vid” shows a video, but for 5 seconds. You need to pass “-t 0” to get the preview to keep running. And after all that… when I turned off the lights, the video was pitch black. I need to figure out how to increase the exposure time if I want it to see stars.

I’ve spent $30 on electronics and the lens so far. I joined the pifinder discord and the creator was incredibly nice, willing to bundle multiple DIY components if I bought them at once instead of charging double shipping from the webstore price. PCBs and some hardware and LEDs will be arriving soon for another $15. The case is 3D printed, which will cost $little in filament. I have a lot of code work ahead of me to save that money, but it’ll be very cool if I can pull this off, with the help of that amazing makerspace.

Possible telescope upgrades

hillexed@email.com (hillexed) — Wed, 06 Sep 2023 20:39:46 +0000

My telescope is pretty good, but now that I have one I’ve been thinking about how to get even better. Here’s what I’ve been thinking about:

#1: Bigger telescope.

Bigger telescopes with bigger mirrors both capture more light and allow you to resolve tinier details. I saw someone made a “Leavitt” telescope, also 3D printed, designed to fit an 8" mirror! My telescope has a 4.5" mirror right now. It cost $30.

An 8" mirror, double the diameter, costs…

$360. Oof.

Another way to do it is to grind the mirror yourself. There’s a long tradition of amateur telescope makers doing that, but it takes lots of time grinding and polishing. The raw materials are still expensive-ish - an 8" circle of glass 1" thick is around $55, and there’s $50 extra of grits and powders you need. For making ultra-big mirrors, there’s some insane people who have started using kilns to take glass circles of normal plate glass and soften them over a mold, so they fall down and make a meniscus shape. It’s a rabbit hole I’ve already gone very very far down researching.

#2: Motorize the mount.

Stepper motors are decently cheap. With some gearboxes to reduce their speed, you could give your telescope the ability to automatically point itself at a target.

There are two kinds of mounts: Alt/Az and Equatorial. Alt/az involve one axis which rotates left/right along the ground, changing “azimuth”, and one axis which rotates up/down to change “altitude”, like a cannon. They’re the simplest to design, and someone has already made one for my Hadley telescope! But I’d need wood-cutting tools and $100 or so for just the wood alone, not to mention electronics.

Equatorial mounts are angled so one axis points towards the north pole, and rotates along the same axis that planet earth does to counteract the rotation of the planets. These are the ideal kind of mount. They’re much harder to design because they have to carry all the weight on those axes and geraboxes, and earth’s spin axis isn’t at all aligned with gravity.

Once you’ve set up motors, you can add “goto” functionality, which lets you press a button and watch as the telescope automatically figures out how to point at something. There’s software called “onstep” for that. I’d love goto someday!

Either type of motorized mount would also let me start taking long exposures to photograph very dim things out in space. An alt/az mount would let me take long exposures of up to a minute. Expose for too long with an alt/az mount and you’ll notice the thing you’re staring at starts rotating in your field of view, called “field rotation”. An equatorial mount doesn’t have that problem, but they’re expensive: a commercial entry-level one is around $700.

Surprisingly, there are people 3D printing decent equatorial mounts! Not many, though - it’s hard to design gearboxes without “backlash” to avoid tiny wobbles. Most are designed to hold DSLR cameras, not heavier telescopes.

#3: Pi-finder

https://www.pifinder.io/ is a neat raspberry pi powered device that looks at the sky and tells you where you’re pointed. It uses a high quality camera to take pictures of the sky, does some magic to figure out where you are, and then uses an accelerometer to track slight nudges. You still need to point and aim the telescope, but it would let me know where I’m aiming.

The most expensive components are a $50 high quality raspberry pi camera, a $20 lens, a $50 GPS USB stick, and an out-of-stock-everywhere raspberry pi 4. Ouch. But I do have a pi 1 lying around… maybe it’ll work? Plus, if I mod the software so I can input my coordinates from the GPS I carry around in my phone, I can save $100 or so.

Will I do any of these? I don’t know!

JUPITER BELTS JUPITER BELTS

hillexed@email.com (hillexed) — Thu, 31 Aug 2023 14:52:05 +0000

THE NEW TELESCOPE MIRROR IS GREAT

BEST $20 I’VE SPENT

On the Night of the True Enemy, I tried to find the ring nebula!

hillexed@email.com (hillexed) — Thu, 24 Aug 2023 23:28:28 +0000

For the record, past me was wrong. That’s not the ring nebula. There aren’t two bright stars aligned like that near the ring nebula. But that’s the prettiest Jupiter I’ve ever taken!

(Why is there a double saturn? I know why now!)

Attacking vibration in Hill Mount v3

hillexed@email.com (hillexed) — Tue, 22 Aug 2023 16:56:49 +0000

Telescope mount v3 is pretty good, but it still wobbles slightly. If I touch or move the telescope, it wobbles a bit before settling down in 2-3 seconds. Before it settles down, Saturn turns into two images of Saturn next to each other.

I can use that picture and do the math to see how much it's wobbling:

https://www.timeanddate.com/astronomy/planets/distance says Saturn is 18.96" right now. That's a second of arc, 1/60 of a minute of arc, which is 1/60 of a degree. That means it wobbles 2 saturns * 18.96 arcseconds/saturn * 1/60 * 1/60 * 2π/360 radians/arcsecond = .0001838 radians. My telescope is about 1.75 feet long from the center point, so since sin θ = o/h, the tip of the telescope is moving side-to-side a distance of h * sin θ ≈ 1.5ft * .00009192 = 0.08403 mm in that picture. Wow, that's about one printed layer line.

How do I stop that?

Right now my telescope mount looks like this. It has a C-shaped top, so the telescope can rotate in and out.

It’s not a full truss - I can’t put a bar between the two tips of the C because that’s where the telescope goes. As a result, the tips of the C are only supported at one side, so they can move in and outwards. Experimentally, if I put pressure on the top part I can make the top part shift slightly in the xy plane.

I tried designing a tiny truss add-on to the front to help resist sideways force for mount v2:

I tried remaking it for mount v3! This time, here’s what mount v3 looks like. The rectangle in the center marks the telescope Bonk Zone, where I can’t put anything without hitting the telescope.

I printed it out, put it together, and noticed it was a very tight fit. Looks like I forgot to add tolerance to the hole sizes. I tried forcing it in anyways to see if it would work, and…

oh well. let’s see if it works once I reprint with bigger holes.

Oh my god there's so many stars in this galaxy

hillexed@email.com (hillexed) — Sun, 20 Aug 2023 06:27:52 +0000

I drove a few hours to visit friends and a bortle 4 sky. wow there were so many stars. You could barely make out an arc slightly lighter in the sky than the rest of it! The Milky Way! Through a telescope, there were much more stars than before and they just kept going and going if you moved the telescope. Saw the plediades too wow many bright stars near each other

No photos of nebulae, my goal, because my openocular malfunctioned and didn’t hold the phone to the camera well. No eye sightings of nebulae like m57 either because oh god the sky is so big and aiming is so hard and you look into the telescope and it’s full of stars and you’re lost

This photo is a 30 second timelapse at ISO 3200, the strongest it can go, from my phone camera placed on a concrete block. Edited to increase contrast and saturation. THAT’S A GALAXY

hillexed@email.com (hillexed) — Sat, 19 Aug 2023 22:26:14 +0000

Jupiter, four Galilean moons, and a blue star!

It could be improved if I was better collimated, but I’m happy I got all 4 of them with the high power eyepiece!

Brightnesses are cursed

hillexed@email.com (hillexed) — Tue, 15 Aug 2023 20:46:47 +0000

Today I learned that astronomers measure star brightnesses in the modern AB system, using (logarithmic) units of Janskys, where one Jansky is 10⁻²⁶ W⋅m⁻²⋅Hz⁻¹. Why is there the extremely cursed Hz⁻¹? Hz is already s⁻¹. Why is it like that. Astronomers, why is it like that. s^−1⁻¹ is just seconds

If you cancel all the units, you get… 1 Jy = 10⁻²⁶ kg m² s⁻³m⁻² s^−1⁻¹ = 10^-26 kg s⁻². …so we measure starlight in the same units as surface tension. If you really wanted to, you could talk about how bright a star is by how much its light would stretch a soap bubble.

I saw a meteor!

hillexed@email.com (hillexed) — Sat, 12 Aug 2023 04:30:41 +0000

I heard there was a meteor shower tomorrow! So naturally I went out today to see it. First I treated it like any other target and tried to find a good gap in the trees to see Perseus, but then I read online that meteors appear in the full sky, not just at the radiant.

So I lay down on the sidewalk, and 30 minutes later… zoop!

The meteor was super underwhelming compared to the time I spent waiting. A blink-and-you’ll miss it streak of a little bit of light. I wish they had a sound like in fiction.

Only bad space today, said the sky

hillexed@email.com (hillexed) — Mon, 07 Aug 2023 14:17:42 +0000

Everything was very blurry today and I kept wondering why focusing didn’t seem to fix it before realizing it was cloudy.

My custom Pico Bluetooth picture taking button worked great though!

A rabbit hole of bluetooth

hillexed@email.com (hillexed) — Fri, 04 Aug 2023 02:25:25 +0000

It all started with an idea for better telescope images.

I take photos using my phone. My telescope shakes when I press the capture button. I have a raspberry pi pico W, which recently added bluetooth. I wonder if I can connect the pico to my phone as a bluetooth device so I could press a button on the pico and remotely take a snapshot.

Bluetooth is a nightmare

the C++ standard is a mess of inscrutable acronyms. Apparently there’s multiple types of bluetooth services, keyboards and mice are called “HID” for human input device, I think bluetooth audio is called HSP for HeadSet Profile. Will that do what I want? Hope so, because I don’t know how to test yet! I found https://github.com/raspberrypi/pico-examples#pico-w-bluetooth, but clicking the links just takes you to some inscrutable C examples from the BTstack library. On the plus side, maybe that means things made for the BTstack library will simply work.

I found a micropython UART example, but my phone wouldn’t connect to it, possibly because it only supports specific services? sigh

I start to get it

okay, I’m starting to get this. bluetooth is many protcols in one, GATT is the meta-protocol that tells you what protocol you should use, each protocol has a number assigned to it like 0x180F for “telling you how much battery I have”, you can only find the numbers by searching a giant inscrutable PDF which doesn’t tell you what anything means.

Oh gosh which service will let me press volume down

Do I want… 0x1812 Human Interface Device (which I know is for keyboards and mice) 0x1843 Audio Input Control 0x1849 Generic Media Control 0x1848 Media Control 0x1855 Telephony and Media Audio 0x1844 Volume Control

Good question! Apparently the list of magic service numbers on https://www.bluetooth.com/specifications/assigned-numbers/ doesn’t actually say what each service does, and you need to go to https://www.bluetooth.com/specifications/specs/ and read a giant specification to find out! Yay!!

Unable to find image voldown.png

This image is all you get for “how to reduce the volume”. It doesn’t even say what Opcode or Change_Counter stand for. To do that I need to go to another paragraph which says “Change_Counter is read from Volume State”??? aargh

A page from the bluetooth HeadSet Protocol dscribing cases where this newfangled bluetooth technology might be used

Unable to find image bluetoothexamples.png

every single one of these 3 pictures is glorious

Pain

Unable to find image volcontrol.png

Ah, of course, the Volume Control Service is 0x1844 in the Assigned Numbers document, but you need to read the Volume Control Service document to learn that you also need Volume State and Volume Control Point characteristics. Naturally now that you know what characteristic names you need, their magic numbers (which are the true things you need) aren’t kept in this document, and you need to go back to the first one into this table. I wish it was sorted by “numbers you need for this service” instead of ALPHABETICALLY

A computer update

My computer can see what bluetooth services my phone supports.

It doesn’t support any of the 18xx fancy Bluetooth Low Energy profiles. NONE of them! There goes my work understanding Volume Control Service.

I gave up trying to use micropython and now I’ll just use C++

turns out, the official bluetooth examples https://github.com/raspberrypi/pico-examples are missing the actual bluetooth examples. you need to build these examples using make to generate the actual example code. of course they also give no instructions for building those examples.

I tried: cmake pico_sdk_import.cmake? Nope, CMake Error: The source directory is a file, not a directory.

cmake .? CMake Error at pico_sdk_import.cmake:55 (message): SDK location was not specified. Please set PICO_SDK_PATH or set PICO_SDK_FETCH_FROM_GIT to on to fetch from git.`

cmake . PICO_SDK_FETCH_FROM_GIT=1? CMake Warning: Ignoring extra path from command line:

“PICO_SDK_FETCH_FROM_GIT=1”

Turns out PARTIAL instructions are in https://github.com/raspberrypi/pico-sdk, and the implication is: they want me to edit the file CMakeLists.txt to add the line set(PICO_SDK_FETCH_FROM_GIT on). WHY WOULD YOU NOT WRITE THIS DOWN

Not all keyboards are made equal

I got an example working! Turns out the unofficial code that lets you code a Pico from the Arduino IDE has its own example classes for acting as a bluetooth keyboard or mouse. You can’t actually see their sample code without going here and looking for a library with BLE at the end of its name, but they work!

I tried sending the HID_KEY_VOLUME_DOWN key and it… did nothing.

After many hours of banging head against wall: I think not all keyboards are made equal, and as part of the bluetooth protocol a device send a “HID report descriptor” which says what buttons it has on it. Of course, HID_KEY_VOLUME_DOWN naturally isn’t part of the keyboard, it’s a completely separate thing called CONSUMER_CONTROL and the arduino-pico’s keyboard class doesn’t include the arcane hex constants that say “I can do consumer control device things like volume down” in its report descriptor. aaaaargh

Protocols all the way down

HID (Human Interface Device, the protocol for Bluetooth keyboards and mice) is a nightmare. It’s ALSO a protocol made of protocols. In fact, at the start of a HID connection the device needs to define its protocol by sending some arcane constants called the device descriptor which says what format all the future messages (called “reports”) will be in. And, of course, there can be multiple types of reports in the same device, with different formats. Turns out you can’t push Volume Down unless the device descriptor says “I have both a keyboard and a consumer control device”. Then you have two types of reports, and you send a report ID with each report to say whether you’re sending a keyboard type report or a consumer control type report. So you define your own custom protocol on top of HID on top of GATT on top of BLE! I’m four protocols down!

Remember, I want to take a picture on my phone. I thought the best way to do that is to press the volume down key.

The Arduino IDE for the Pico has a BLE keyboard library hidden in the examples. No BLE Consumer Control example library. Other people have Consumer Control libraries, so I spent a long time trying to modify the device description from “I am a keyboard” to “I am both a keyboard and a consumer device” and trying to figure out how to send the right report format.

Remember that report ID? That’s how normal Bluetooth works. Turns out all my effort was for naught because the BLE functions physically didn’t have a place to put that report ID. Turns out HID with BLE handles multiple report formats in a slightly different way compared to HID over normal bluetooth. And that’s when I realized something.

The end

I embarked on this quest to press the volume down button. But I don’t need to press the volume down button. I realized I could just click the take picture button with a mouse instead!

So I looked at the Bluetooth mouse library, and successfully used it to make the mouse move!

Sure, the “move to absolute position” didn’t work, and packets kept dropping if I sent them too quickly, and you can only move 128 pixels in a single move, and I can’t know where I am on the screen without moving to the bottom left repeatedly to reset the mouse position…

But I can finally press a button on my Pico, and watch the mouse move to the corner, then move to and click the “take picture” button! I declare: ABYSS SUCCESSFULLY GAZED

An idea for better images

hillexed@email.com (hillexed) — Thu, 03 Aug 2023 22:59:32 +0000

Welcome! Welcome, new galaxy!

hillexed@email.com (hillexed) — Wed, 02 Aug 2023 18:43:00 +0000

I got the Andromeda galaxy!!!

Aiming the telescope was a nightmare. “I’ll use a star app to aim!” I thought. I tried downloading Stellarium, it complained about a Google Play error. I downloaded SkEye, and it had some weird gyro issues because it expected the phone to be pointing in the same direction as the telescope, but I use my phone camera to take pics so it was mounted sideways looking at the telescope’s eyepiece. I didn’t really know my constellations, so it was hard to figure out what stars I could see in the light polluted sky were which stars on the app, and the part of the sky where it was seemed perfectly dark with no landmarks to aim at. I ended up pointing my telescope at a bright star, aiming upwards to what I thought was the right altitude using my mount v3’s degree markers, then rotating left/right at random patches of dark sky, shooting some four second long exposures, and hoping it would appear out of the gloom.

And somehow, looking through my pictures, I got it.

And then I immediately lost the telescope’s aim trying to see Andromeda with my eye and despite like 10 tries never managed to find it again.

I tried stacking my 3 exposures in Krita in Addition mode, but it didn’t seem to work well, so you’re looking at the best 4s exposure lightly edited to increase contrast.

Pictures from My 3D Printed Telescope, with Mount v3

hillexed@email.com (hillexed) — Sat, 29 Jul 2023 18:12:59 +0000

I finally finished Hill Mount v3, so I put it to the test. I got the clearest phone-cam Saturn I’ve ever seen! Wobbles still exist if you touch the telescope, but the wobbles are much smaller now and go away if I wait a few seconds or use a short exposure time.

Before the wobbles settle down, if you take a picture with a big exposure time, the wobbles cause the image to have two Saturns.

I think that confirms my theory that the long stretched out Saturn I saw with Mount V2 was caused by a tiny wobble. Overall, it's not wobble-free and could use some damping, but I declare Mount v3 a success!

I also got Jupiter again, and I could see two Galilean moons by eye but I couldn’t capture any using camera. I couldn’t see any of the stripes, though. Jupiter is way more featureless than I expected; I wonder if there are any cheap filters I can use to see more of the stripes.

In the last picture, I took a very long 4s exposure of Saturn. The earth’s rotation meant, Saturn blurred into a streak, but take a close look - there’s a smaller streak right next to it following Saturn! I think that’s one of its moons, possibly Titan! It’s so cool that I can see it from my backyard.

Things to improve:

Make the mount even stiffer?
How do I add damping, to make vibrations decay over time?
Just as I was writing this, I discovered some smudges on my eyepiece. Oops! Maybe that’s adding some glare. Hopefully once I clean that I can get even sharper images!
Try image stacking?

Telescope mount v3: Complete!

hillexed@email.com (hillexed) — Sat, 29 Jul 2023 01:19:05 +0000

This mount is my stiffest one yet!

Changes from last time:

uses steel EMT instead of wooden dowels, for extra stiffness
flat sides so you can see the degree markings
deeper and more visible degree markings

It feels pretty darn stiff! Unfortunately, tapping the side still makes the telescope wobble. It’s definitely much less wobble than before, though. Maybe it’ll be enough for clear pictures!

Maybe it wasn't the cheap filament's fault

hillexed@email.com (hillexed) — Fri, 28 Jul 2023 17:22:10 +0000

maybe this orange filament just likes to warp. Anyway, all parts printed!

Telescope mount v3 is printing!

hillexed@email.com (hillexed) — Wed, 26 Jul 2023 18:47:58 +0000

comment “safe printing mx mount” to lend it your energy

Here's a cool cutaway of how I'm holding the rods in place

hillexed@email.com (hillexed) — Wed, 26 Jul 2023 18:21:33 +0000

Here’s a cutaway view of my telescope’s 3D printed bases to hold rods in place. The rods go into the giant cylinders, but how do you stop them from slipping out? Insert a nut in on one side of the hole, and then screw it in from the other side. The cut in the top means the entire piece bends to hold the rod in tightly! This is so annoying to design because my rods are so close together you need to make sure that the cutaway for the nuts and screws don’t accidentally cut a hole in the wall of the places where the rods go.

Hope it works.

Gas giants, wooden wobbles

hillexed@email.com (hillexed) — Thu, 20 Jul 2023 17:07:03 +0000

I took my new wooden-dowel telescope mount for a spin, and got pictures of Jupiter and Saturn with my high-power eyepiece!

I took many pictures, and a few videos. I also figured out how to control the shutter speed on my phone’s camera, and got many photos at 1/40s shutter speed. Using a smaller shutter speed takes the planets from blinding white blurs to circular colored blurs, I assume because it lets in less light. It can make a planet go from blindingly white to almost completely disappearing into the night sky. However, my phone doesn’t let me control those settings when taking a video. The second and third images show the best raw pictures I got.

Saturn through my telescope had this weird diagonal smear to it. Since I’ve been fighting vibration issues with my wooden-dowel mount, I think it’s a very small high-frequency vibration from left to right causing that problem?

Then I tried using image processing software, Pipp plus autostakkert plus registrax, following this video tutorial. There were some shenanigans because Pipp’s site got taken down and I had to find a backup, but eventually I made the heavily processed Jupiter in the first image. Sadly, I haven’t figured out how to stack my photos because the software complained my images were different sizes (from before and after I pressed the “save as raw” button), but I was able to take a video of Jupiter without the high shutter speed setting and process that. It was a bit underwhelming - I went from dim blurry sphere to SLIGHTLY STRIPED dim blurry sphere! Wow! If there’s one thing I learned I suppose it’s that my telescope was out of focus.

I hope the pictures will be improved if I make a new mount using metal EMT pipes.

Another Way Forward

hillexed@email.com (hillexed) — Sat, 15 Jul 2023 15:31:44 +0000

Last telescope update I finished mount v2 and was stuck because it wobbled. One way to try again is to make the rods out of metal EMT instead of wooden dowels. I bought a hacksaw and spent a while hacksawing my EMT to the right length before learning there were specific pipe cutting tools that were far easier to use. Oops! I’ll also need to redesign my mount to use the larger 0.706in EMT pipes.

Recently I went to my local astronomy club for the first time! It was filled with old retirees who could recognize messier objects by sight like I recognize pokemon. Incredible! As I talked about my telescope, eventually I nerd-sniped someone into helping me brainstorm how to resist the shear from the top twisting. They suggested turning the bottom part of the mount into a shear-resistant two-level truss, so that the vertical rods extend upwards to support the top part.

Apparently a truss is stable because of tension lengthwise along the rods - a theoretical truss can freely rotate at every vertex. These theoretical rods have no bending resistance. In practice of course rods do have bending resistance, and that’s what would resist my twisting. It’s worth a shot.

I designed some parts that include at least part of those truss structures to see if it would help. I have some wood left over, so I’ll test if this makes the mount any more rigid before designing an EMT mount. Hope it works.

A new rod challenger

hillexed@email.com (hillexed) — Tue, 11 Jul 2023 15:49:23 +0000

Update: I’ve learned about the existence of EMT conduit, which is steel so it’s much stiffer, cuttable with a handsaw, and most importantly way cheaper than the aluminum tubes I bought before!

The downside is it’s sized in nominal diameter, which means lying. The size “1/2 in” has an outer diameter of 0.706 in. But I’ve faced nominal diameter before and this time I’m prepared. Let’s try this.

Telescope mount v2: complete!

hillexed@email.com (hillexed) — Wed, 05 Jul 2023 21:50:20 +0000

It didn’t work. The main type of wiggling I was trying to stop is the top part twisting around the z axis compared to the bottom part. This new mount stood up well, but if I placed the telescope on the mount and gave it a sideways nudge, the telescope would wiggle from side to side at a period of about 1/4 s. It does seem less wobbly than my previous square mount, but it’s still pretty wobbly.

On the plus side, I added little degree markers so you could see what elevation your telescope is pointed at. I like them.

I’m stuck as to where to go from here. How do I change this design to make it more rigid? I’m out of ideas. Maybe the wooden dowels are too flexible and I need to buy aluminum rods? But I can’t cut aluminum to the right size. Damping exists as a theoretical idea, but how do I add some in practice?

Telescope mount V2 construction begins!

hillexed@email.com (hillexed) — Wed, 05 Jul 2023 17:22:59 +0000

Starting to build telescope mount v2! I’m using 0.5in rods, and v1 had holes 0.52in wide. This one has holes 0.51in wide, and that was a mistake, it made getting the rods in there so much more annoying.

hillexed@email.com (hillexed) — Tue, 04 Jul 2023 18:33:15 +0000

I was unsure about how to model this part to make it non-wobbly so I looked up and watched a full lecture from MIT OCW about vibration reduction. it didn’t really help but now I understand that when you bend a stick, the outer part expands and the inner part shrinks and so by making bigger areas farther from the bending (weird) you can resist shrinking and growing a bit more. how do I apply that to a complicated multi-beam twisting telescope part? unsure

Triforce of Space

hillexed@email.com (hillexed) — Tue, 04 Jul 2023 01:55:19 +0000

Telescope mount v2 has 3/4 pieces printed! The pretty colors are because I ran out of filament twice

hillexed@email.com (hillexed) — Sun, 02 Jul 2023 16:40:01 +0000

This redesigned telescope mount part is a good shape

It didn't work

hillexed@email.com (hillexed) — Sat, 01 Jul 2023 20:41:07 +0000

I put everything together for version 1 of my telescope truss mount. It stands! It was also an inch too wide for the telescope to properly rest on it. I had to rotate it the wrong way so it could fit on the stand for the picture. Aargh.

Some of the clamps did grip the rods well, some of the clamps didn’t. The base did feel pretty solid, but the top part is still pretty wobbly after full assembly. I’ve learned a few lessons:

Longer holes for more grab surface area
Add some holes to screw my mount into the floor, which will stop flexing in addition to being a requested feature
Right now I have 0.5in rods, and they’re fitting in 0.52in holes. If my mount is wobbly, maybe I should decrease the hole tolerance to 0.51in? It’s a tradeoff but may be worth it
Redesign rear base back grabber, it doesn’t grab properly
It’s 6.5 inches wide from outside to outside, not 7.5 inches. :(

Now, to design version 2!

hillexed@email.com (hillexed) — Wed, 28 Jun 2023 18:38:04 +0000

time to assemble

My telescope mount prototype is finished printing!

hillexed@email.com (hillexed) — Wed, 28 Jun 2023 18:23:59 +0000

Came out with some blobs and very stringy, which isn’t good, but they came off with some pliers. Time to go cut my dowels to size and see if it all fits

Designing a new mount

hillexed@email.com (hillexed) — Sun, 25 Jun 2023 20:53:32 +0000

My 3D printed telescope has a problem: it’s very wobbly. That means it’s hard to point the telescope at a planet and have it stay pointed at the planet. It also means I can’t focus it well, or take good pictures through my phone.

The telescope itself is fine, but the mount is the problem. There’s a 3D printed mount included in the files with the telescope, and I built that 3D printed mount (after trial and error and discovering pipe sizes are a lie ). However, the creator of the telescope doesn’t actually use the 3D printed mount - he has a mount made of solid wood. I don’t have a wood saw, so I can’t build that.

There’s another mount named Marci’s Mount, made by Marci, which involves using a vinyl record as a turntable so you can rotate the telescope along azimuth (very cool). It uses a sort of truss design with cross-braces to be even more stable, but you need a drill and a saw to use the turntable part. I don’t have either, which is a shame because it seems like a very cool mount.

I decided to try making my own mount. Halfway through studying that one, I discovered a third mount which is very clever and uses more rods to make a truss shape for extra stability. It also uses a clever screws-squeeze-the-plastic design to have more surface area grabbing the rods for more friction.

My plan now is to make my own mount, copying Ivan’s truss design but increasing the size of the bottom part for added stability. Hopefully that’ll make a more stable telescope!

hillexed@email.com (hillexed) — Fri, 23 Jun 2023 19:12:05 +0000

I woke up early and saw Jupiter and Saturn!

Thoughts on the observing: I have two eyepieces, a high power 6mm and a low power 25mm. I couldn’t get a picture of the planets with my high power lens because my mount is too wobbly and I couldn’t find the planets once I mounted my phone on the telescope. I did see Jupiter through it amidst the wobbling, and it looked like a featureless white blob. I could barely make out some stripes, whichwas cool!

To get at least some pictures before the sun rose, I switched to my low power lens. Using that, I found Saturn! And as the sun began to rise, I switched back to Jupiter, and I could see it as just a big round bright circle… but also with some of the Galilean moons next to it! And then morning clouds rolled in and covered everything and I went home.

Instead of taking pictures, now I’m taking videos so I can extract the good frames afterwards. I took a video of Saturn while trying to focus the telescope, hoping I’d get a good level of focus somewhere. Turns out my phone’s autofocus didn’t like Saturn and kept trying to focus incorrectly.

What that means is: as cool as these photos are I need to aim my telescope better, I need to focus better (I did find the button to turn off phone autofocus!), and if I do that, I can get even better photos with the higher powered zoom lens! There’s a ton of potential for improvement.

hillexed@email.com (hillexed) — Tue, 20 Jun 2023 08:34:18 +0000

I woke up early to go see Jupiter and Saturn and turns out it’s still really really hard to align this telescope! I took videos in the hopes I’d catch at least one good frame, now to review them and see if that’s true. I got a decent video of Saturn in my low power lens, hope it shows up well as rings instead of fuzzy blob

Telescope upgrade 2: Electrical tape and openocular phone mount

hillexed@email.com (hillexed) — Thu, 01 Jun 2023 15:05:23 +0000

(Part 3 of my adventures with my 3D printed telescope! Previous part)

I tried adding 3 upgrades, but only two of them worked. Check out an amazing moon photo below!

Upgrades

My mount is very wobbly. To reduce the wobble I had two ideas: first, place wooden dowels along the diagonals of the sides to make the mount more rigid, and second, print an openocular.com phone holder so I didn’t have to touch the telescope to take pictures with my phone and wobble it.

I bought three more wooden dowels, then I designed two versions of 3D printed pieces to hold the diagonals in place. After printing, they didn’t fit my base. I forgot to account for the fact that there were plastic parts at the top and bottom of the pipes that would stop me from attaching them there. In the end, I just taped the dowels to the mount using electrical tape. I think it worked pretty well to make the telescope rigid, but it didn’t stop the wobbling.
The openocular.com phone mount is a 3D printed piece that lets you place a phone up to an eyepiece. That works for me, because that means I can place my phone in there then step back and the telescope’s wobbles will settle down! It still wobbled, but the wobbles died down after a while. Nice.

The mount itself is very fiddly, and it doesn’t help that if I see black through my phone, I can’t tell if the mount is aligned wrong and my phone isn’t pointed in the eyepiece, or if the mount is aligned correctly and the telescope is just pointed at dark sky. It’s also hard to focus with the mount on because the phone will also try to autofocus.

The open ocular and eyepieces are heavy, and plastic on plastic is slippery. If I put the open ocular on, the entire telescope rotates down because of the weight. To fix that, I unscrewed and adjusted the position of the center piece on the rods until it balanced. But I also added some electrical tape to the curved circular rockers, to make it less slippery, and that was a massive improvement. Now the telescope stays in place much better. I wholeheartedly recommend doing this.

Using all these upgrades, I took this picture of the moon using the phone mount.

Wow! You can see so many craters!

Telescope upgrade 1: basket

hillexed@email.com (hillexed) — Fri, 26 May 2023 21:59:57 +0000

(Part 2 of my adventures with my 3D printed telescope!)

I printed a collimation helper and a basket! The collimation helper helped me find out that I thought I was collimated, but was actually misaligned. With proper collimation, I went out again and took this new picture of Venus.

To the eye, collimation didn’t seem like it did anything, because my telescope and its mount was just so wobbly it looked the same to the eye as before. But my phone pic definitely seems better - now you can see the waxing gibbous shape instead of bright dot. Don’t know why.

I also found out “open ocular” is a 3D printable mount to hook a phone up to a telescope. I’m making one now. Hopefully that’ll help make it less wobbly?

Today I learned about Living Newspapers

hillexed@email.com (hillexed) — Thu, 08 Dec 2022 20:36:09 +0000

As a tiny part of the New Deal, Hallie Flanagan helped create the Federal Theatre Project in 1935, where the US government funded unemployed actors to make free plays available to all. A big part of those were Living Newspapers: researchers became playwrights and wrote about current events lifted from the headlines to inform people.

The very first Living Newspaper was a hilarious tragedy. “Ethiopia” by Arthur Arent was all about how being invaded during the Second Italo-Ethiopian War was ravaging the country. Hilariously, it got exactly one dress rehearsal (the press was invited, it got good reviews), and then the US State Department cancelled it before its first showing, arguing that it was bad to show other world leaders, specifically this guy named Mussolini, in a bad light. And they only found out because someone in the production team tried to make the play more realistic by requesting a recording of one of President Roosevelt’s speeches, tipping off Washington…

Thankfully, other Living Newspapers about domestic issues became huge successes. Eventually the Federal Theatre Project fell into a fate that seems eerily similar to today: wealthy people got mad that it gave money to those who were seen as not deserving it despite being a tiny fraction of the budget, it was accused of being too communist after things such as plays which revolved around housing inequality and farmers, and the program was cancelled in one of the first victims of McCarthyism :(

(Source: https://doi.org/10.2307/3204873 , but I only found out about this from seeing the book “Furious improvisation : how the WPA and a cast of thousands made high art out of desperate times” by Susan Quinn in a library search)