| 1 min
| 145 words
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!
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| 1 min
| 160 words
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 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.
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| 1 min
| 31 words
Two hours of mirror grinding brought me from the first pic to the second! The center zone got so big! It’s so much straighter! I’m much closer to a spherical mirror!
| 1 min
| 41 words
Unable to find image IMG_20240301_215655700~2.jpg Unable to find image IMG_20240304_154953737~2.jpg Two hours of mirror grinding brought me from the first pic to the second! The center zone got so big! It’s so much straighter! I’m much closer to a spherical mirror!
| 1 min
| 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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| 1 min
| 119 words
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.
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| 2 min
| 234 words
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.
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| 2 min
| 254 words
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 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.
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| 1 min
| 152 words
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.
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| 1 min
| 162 words
Unable to find image IMG_20240131_170731472_1.jpg Unable to find image IMG_20240131_172405688_1.jpg 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.
Read More