Nikon 500mm f/8 Reflex

[Astro]

the bokeh/backround blur of a mirror lens is so ugly and uneasy.... i can´t stand it.

i tried a mirror lens  for canon too.. i admit it.. but i sold it after a few days.

[paul13walnut5]

I have the Sigma 600mm f8.

Needs a heavy steady tripod (video type is more stable, level head with bowl, adjust camera level via tripod ring) good light (it has poor contrast at best, as light starts to fade the naturally low contrast just washes out images taken with the mirror lens, easily fixed with a bit of gamma correction)

I get best results with stills when I pre-focus and wait for the action.  Magic Lanterns focus trap feature may be useful for those considering a mirror lens.  Use a cable release and MLU or live view mode.

Focus, let the wobles settle, check and reset focus.

You can get a sharp shot with a mirror lens,  it just isn't all that easy.

It also makes a brilliant video lens (in good light) but again, requires proper supporting.

They are a good way to get extreme reach (600mm x1.6) but can be very frustrating to use.

If it's a once in a lifetime shot, and / or you don't like MF, then look elsewhere.

[Mt Spokane Photography]

I have the Sigma 600mm f8.

Needs a heavy steady tripod (video type is more stable, level head with bowl, adjust camera level via tripod ring) good light (it has poor contrast at best, as light starts to fade the naturally low contrast just washes out images taken with the mirror lens, easily fixed with a bit of gamma correction)

I get best results with stills when I pre-focus and wait for the action.  Magic Lanterns focus trap feature may be useful for those considering a mirror lens.  Use a cable release and MLU or live view mode.

Focus, let the wobles settle, check and reset focus.

You can get a sharp shot with a mirror lens,  it just isn't all that easy.

It also makes a brilliant video lens (in good light) but again, requires proper supporting.

They are a good way to get extreme reach (600mm x1.6) but can be very frustrating to use.

If it's a once in a lifetime shot, and / or you don't like MF, then look elsewhere.

+1, exactly my experience.  A good option for a person on a tight budget, but you will work for the best images.  i was going to list it for sale, but i'm going to wait and try it on my 1D MK IV with the new focus screen next week.

[Mt Spokane Photography]

My Ec-S focus screen came today for my 1D MK IV.  I popped it in, and my manual focusing did improve, but still not equal to AF or live view. 
I played some more with hand held images from the 500mm mirror lens, but, for me, it was a exercise in frustration trying to setup a good exposure and then getting a sharp image.  I ended up with only two of 20 or more that were presentable, and these were not all that sharp.  I was using shutter speeds of 1/1500sec or more, so I had the ISO cranked up, even in very bright sunlight.
I gusee I'll list it on Craigslist or ebay, my vision is not up to it, and, my 100-400mmL blows it away.  I can even crop my 100mm macro images and get better.