Collimating a 400mm f/20 Classic Cassegrain

400mm f/20 Classic Cassegrain on collimation bench

We all know that collimating a telescope that has multiple curved mirrors is Black Magic. I’ve tried it and I can happily confirm I am… not a witch.

Here’s a 400mm f/20 Classic Cassegrain. The primary mirror is a parabola and the secondary is a hyperbola. And if you do the maths, the focal length really is 8000mm!

The last stage of manufacturing for this monster was collimation. To do this, Catalin (definitely a wizard) set it up on a bench so it was facing a flat mirror on the wall opposite. Using an artificial star and a beam splitter, he sent a beam of light from the eyepiece, bouncing off the secondary, back to the primary, out to the flat mirror, back to the primary, then the secondary and through the beam splitter to the eyepiece. This allowed him to align the telescope on the bench first, and then to adjust the mirrors.

The scope has now been crated up and shipped off to its new owner in Europe.

    Need Expert Advice?

    Visual Astronomy, Astrophotography, Microscopy and Macro Photography can be a little complicated sometimes as there are a lot of options. If you'd like to check something before you purchase just let us know and we'd be happy to help!

    Enquire now or call us (03) 9042 2293

    Recent Articles

    For sale – refurbished QHY600M-Pro camera

    QHY600M-Pro - used
    FOR SALE: QHY600M-Pro Condition: external marking but internally refurbished by QHY. No accessories included. Price $7000 (new price is around $14,000) Contact: Diego on Facebook at https://www.facebook.com/dcolonnello Details This is a…
    Read More