Mastodawn

Astronomy sidequest: woodworking!

A few weeks ago I broke the DIY table I built to polish telescope mirrors, so I added some more screws and rebuilt it. It must keep mirrors at elbow height during polishing, and is weighed down to withstand sideways forces from friction. I copied the truss design from the guide on https://stellafane.org/tm/atm/mirror-general/materials.html , but this rebuild uses two screws per strut for added rigidity. I have employed advanced metrology equipment (pictured) to verify its surface isn't tilted.

hillexed Jan 24

It has been several months of assembling and tinkering and troubleshooting to get here, but my bath interferometer is finally working! Now I can feed these images of concentric circles into software and analyze the shape of my mirror down to tens of nanometers!

These pictures show a laser beam, split in two by a beam splitter cube, interfering with itself. The dark zones show regions where one beam travelled an integer plus a half number of wavelengths farther then the other beam, so when they add back together they're out of phase and cancel out. A linear polarizing filter on my camera I got helps equalize the brightnesses and make the pattern clearer. The resulting pattern can be interpreted almost like a topographic map of the mirror, where a single ring is all at the same "height" from my 3D printed testing apparatus.

#diy #interferometry #hillescopemaking

hillexed Jan 13

The laser beams in my interferometer seem to have a dark stripe down the center that makes it very annoying to align. I think it's an issue with the laser itself, since even without the rest of the optics the laser outputs a weirdly off-center beam

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hillexed Dec 26

several hours of fixing my code and remembering how electromagnetic waves are constructed later, my simulation works!
Green means strong electric field, red means strong magnetic field. Yee

hillexed Nov 26

A few replacement parts later, it's interferometer time!

This is a Bath interferometer that splits a laser into two parts, reflects off a mirror, and then recombines to make an interference pattern. The overlap of those two circles should show an interference pattern of stripes across it which shows me a topographic-like map of the mirror's height in units of 600 nanometers.

hillexed Oct 26

It's very hard to aim a telescope with its zoomed in view. I got this finderscope (a smaller, wide field telescope) for $30 used, but it sat on a shelf for a few months. It took a few iterations, but I finally designed a mount that allows my 8" scope to hold both my PiFinder and the finderscope at the same time!

#hillescopemaking #diy #astronomy