2025 amateur optics / astronomy updates

Looks like it’s that time of the year again ! See last year’s update.

This year was quite calm if we compare last year’s backlog and this year’s backlog. But in the background a lot still happened.

• I figured in January 3 different 6” f/5 mirrors sold as defective on Aliexpress : they indeed were, and had absolutely horrendous figures. One had a central hill 4 microns tall. This is an eight lambda hill and could be felt without any hesitation by dragging your finger on the surface. Those were quite challenging to polish, because the glass behaved weirdly. I managed to bring them all between 0.92 and 0.95 strehl. The 0.92 one kept generating astigmatism, I suspect its glass wasn’t free of tensions.

• Another one a 6” f/5 mirror sold as a sphere on Aliexpress, was figured to a parabola in early spring. To my surprise, it came as a textbook clean sphere better than lambda/6, and brought me some kind of polishing epiphany : it is the first time I was able to figure a mirror from start to finish in an afternoon. I worked mirror on top, and did 4x5 minutes of parabolizing, wide Ws along the classic Texereau fashion, and the parabola just came in perfectly, strehl jumping to 0.4, 0.6, 0.8, then 0.95 without any setback. This is the textbook parabolizing process and I was super stoked to finally experience it after five years of mirror making.

• Two of my friend became pros ! Paul is working under the name of Gallifrey Optics, and produces optics and full telescopes, and Raph works under the name La 3eme dimension and produces compact travel telescope structures that also happen to be open-sourced. I’ve tried to help them the best I could by sharing their projects, giving critical feedback, and helping them build digital tooling – Paul is my only user for ATM-Buddy, the “telescope maker buddy” mobile companion app, and Raph went from a few notions of HTML to building his own website, first alone, then LLM-assisted. I gently nudged him to Astro then suggested he could use a robot’s help after he took on enough knowledge to be efficient.

• I’ve missed practicing myself for most of the year, then went for a bit of a rush to build a tiny 76/300 pocket scope that I shared on HN. Once again HN delivered and I had the pleasure of interesting finds or discussions with new people. This website holds a lot of social power if you publish to it with honesty and an open mind. The mirror was very bad and I re-polished it.

• In the same vein, since mirror making time was very sparse, I started cloning the ubiquitous Rigel Quikfinder to provide an open-source version. This is a great reflex finder and the community lacks a do-it-yourself option. This is still a work in progress but shows potential.

BIG projects are still stalled (my 16” mirror is still waiting to be figured, my refractor lenses that ask for a bit of equipment construction too), but a few things got done anyway.

See you next year !