600mm Mirror Lens for Astro?

[jACK101]

I am considering buying a 600mm Sigma Mirror Lens for use with my Canon 5D Mk1 full frame camera. I also have a CPC 925 Telescope but the focal length is sometimes a bit long for deep sky work. Would the 600mm be suitable or are there better alternatives?

 

Thanks

[michael.h.f.wilkinson]

At F/8, the Sigma 600 mm is not that fast. I would prefer going for something like a 400 F/5.6, which Sigma also made

[Louis D]

I haven't tried one at night, but I had a 500mm F/8 Sigma mirror lens that had abysmal contrast in the daytime.  I gave it to a friend and decided to stick with unobstructed lenses for daytime use.  Perhaps on high contrast targets like starfields and clusters the low contrast wouldn't matter.

[RichM63]

I have a 500mm Samyang f6.3 mirror lens, which might be a better option. Not tried it at night, I suppose I should.

[kendg]

I have an Opteka f6.3 500mm. It's a bit tricky to focus but it works not too bad. At least it wasn't very expensive.