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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
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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.
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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.
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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
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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!
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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.
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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!
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