7 ms·

This is only tangential to the point raised by the article, but I encourage anyone interested to try to make and measure a mirror, it's a really rewarding proce

This is only tangential to the point raised by the article, but I encourage anyone interested to try to make and measure a mirror, it's a really rewarding process to take a round slab of glass to an almost perfect parabolic surface (or at least within tolerance). Nowadays, most amateurs also use interferometry which could be appealing to HN crowd too. I haven't followed this rule, starting small and easy, and my first mirror took me 19 months. The second of similar difficulty took about 2 months. Looking back, I find it strange to have taken such a difficult first one, because I do start small and build upon small steps in software.

Wistar 4y ago
When I was very young, my father ground a 6" mirror with a 48" focal length. I vaguely remember him walking around a table for hours every night for weeks. The first mirror was a failure and he had to start again. The finished telescope was—and is still—a marvel although the mirror now needs to be re-silvered. Alas, the light pollution in my area cannot be so easily remedied.