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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 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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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.
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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.
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