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| 72 words
Here’s my mirror in a Ronchi test and a Foucault test. I’ve managed to reduce the turned down edge to a very small area but it’s still there, visible in the ronchi as hooks at the edges and in the Foucault as a slight black zone at the bottom left of the image. I’ve also managed to dig a huge hole in the center of the mirror trying to fix that edge…
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Unable to find image IMG_20240217_151229501.jpg Unable to find image IMG_20240217_151451964.jpg Here’s my mirror in a Ronchi test and a Foucault test. I’ve managed to reduce the turned down edge to a very small area but it’s still there, visible in the ronchi as hooks at the edges and in the Foucault as a slight black zone at the bottom left of the image. I’ve also managed to dig a huge hole in the center of the mirror trying to fix that edge…
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| 57 words
It looks like there were pockets of air under the pitch. Leaving it alone for a week meant the bubbles seem to have popped and some areas sank downwards.
This turned down edge is slowly going down but it still feels like an endless quest with no end in sight.
Total grinding time so far: 8 hours
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Unable to find image IMG_20240213_161218564.jpg Unable to find image IMG_20240215_191112369~2.jpg Unable to find image IMG_20240213_152657507_HDR_1.jpg It looks like there were pockets of air under the pitch. Leaving it alone for a week meant the bubbles seem to have popped and some areas sank downwards.
This turned down edge is slowly going down but it still feels like an endless quest with no end in sight.
Total grinding time so far: 8 hours
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| 201 words
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.
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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!
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.
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| 85 words
you can mirror grind in two ways: mirror on top or tool on top. Apparently if you have a turned down edge to fix it you do center over center strokes with amplitude 1/3 of the length, according to a video by Gordon Waite. I did it for two hours yesterday and made little progress. Today I took another look at the video and noticed he was doing it tool on top.
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| 1 min
| 85 words
you can mirror grind in two ways: mirror on top or tool on top. Apparently if you have a turned down edge to fix it you do center over center strokes with amplitude 1/3 of the length, according to a video by Gordon Waite. I did it for two hours yesterday and made little progress. Today I took another look at the video and noticed he was doing it tool on top.
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| 99 words
Figuring sucks.
My mirror should be a sphere. It isn’t a sphere. I’ve introduced a “turned down edge”, where the edge is ground lower than the rest of the mirror and you have to remove all the glass in the center to fix it. You can see it in these ronchi test pictures, each taken after a few sessions of 30 minutes of total polishing. The straight lines show that part of the mirror is spherical.
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Unable to find image IMG_20240201_235110759.jpg Unable to find image IMG_20240201_232158081_1.jpg Unable to find image IMG_20240204_160010077~2.jpg Unable to find image IMG_20240204_183617859~2.jpg Figuring sucks.
My mirror should be a sphere. It isn’t a sphere. I’ve introduced a “turned down edge”, where the edge is ground lower than the rest of the mirror and you have to remove all the glass in the center to fix it. You can see it in these ronchi test pictures, each taken after a few sessions of 30 minutes of total polishing.
Read More