Improvements of Samyang 800mm f.8.0 Mirror lens

Started Jan 7, 2014 | Discussions thread
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NoRules Senior Member • Posts: 1,454
Improvements of Samyang 800mm f.8.0 Mirror lens

I'll keep this short. I have a more elaborate post on astrophotography forum, but interest over there was rather low.

I have bought a Samyang 800mm f.8.0 mirror lens for the second time, because this time I think I know how to fix the issues with it. The first one I sold. Now, as I'm occupied with astrophotography, the design is very intriguing.

This lens has a (true) reputation for being impossible to focus, and blurry to the point that there is no micro contrast and no low contrast in the images. Some of these issues can be solved in PP and focus bracketing, but I think I have found an easier way. I have made a focus tuner and a rotating (off-set) aperture. A lens shade is on its way. Here is the images of the gadgets and the mounted focus tuner (FT). No permanent mods to the lens required.

Image shows focus tuner and aperture for mirror lens at f.11, f.16. and f.22

I have done some initial testing, but today the rain finally stopped, and I could go out on the porch and do some real world long distance testing. Fist I did 10x Live view focusing without the FT and tried this five times. The best image of these is the bottom right, and like we are used to; blurry and slightly out of focus. Top right is taken with FT, and here we see some of the potential of this lens. Add the rotating aperture, and the result is a big improvement (bottom left f.11 and FT, top left is f.16 and FT). It is no where near the $10.000 glass, but for $180 it's good enough for me. The low weight and short barrel makes it far better than my 400 f.5.6 and 2x TC For astrophotography. Shutter times in this image is 1/45 to 1/10! Camera is Canon 60Da and crops are 100% at 400 ISO. Equi. focal length of 1200mm. Distance to target is 3km.

Here is a PP'ed version of the target with enhancement of contrast. BW because I like it

Canon 60Da, Samyang 800mm Mirror lens with FT and f.16 rotating aperture.

It's not a revolution by any means, but this lens can be improved a lot if one is on a budget. I'm still waiting for clear skies, because this is the only 800mm I can think of that will work on my light Equatorial motor. Its like a pocket telescope! Now modified I expect better results than last time.

Ideas for more improvements are welcome.

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Free your mind, and your camera will follow...

 NoRules's gear list:NoRules's gear list
Pentax K-01 Leica M-Monochrom Pentax Q7 Pentax Q-S1
Canon EOS 60Da
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