Collimating a Classic Cassegrain telescope – or any telescope with more than one curved mirror – is not easy. Catalin from CFF Telescopes collimated this 400mm f/20 with an artificial star, a beam splitter and an optically flat mirror.
Reflectors
What is retrograde motion in a planet?
Every month, I present a talk at the Astronomical Society of Victoria on what’s up in the sky. They’re uploaded to YouTube and a few other video sites, and I…
Read MoreImaging galaxies using Hydrogen Alpha
Taking monochrome images of a galaxy in red, green and blue light allows you to make a full colour image, in a similar way to your eyes detecting the three colours and your brain combining them in the colour image. But you add exposures taken through a Hydrogen alpha filter, which draws out emission nebulas in the galaxy.
Catching a Lunar Eclipse using a remote facility
For the Lunar Eclipse of September 2025, Bill used a remote facility that Sidereal Trading had installed at a club in Victoria to get a sequence of images. It didn’t go quite to plan, but he got the shots anyway.