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IR/UV cutoff on Samyang 135MM F2

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#1 pbunn

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Posted 21 July 2018 - 08:50 AM

I have purchased a 135 MM F2 Samyang lens and plan to send it to Ron at Moonlight to add his belt focus motor assembly.

 

It will be piggy backed on a long focal length scope at a remote dark site.

 

I will be using it with a QHY OAG M and a ZWO asi 1600 C one shot color camera. I have very limited back focus with with the Precise Parts Nikon to 54 mm adapter so I don't have much  room (maybe 3 mm) for a UV/IR filter.

 

I have a 77mm UV/IR filter for the front of the lens and likely will use it there . Any ideas on something better?

 

Thanks


Edited by pbunn, 21 July 2018 - 08:51 AM.


#2 calypsob

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Posted 21 July 2018 - 12:53 PM

That is awesome I hope you share some pictures of what it looks like with the Af unit. Since you are sending it away you could also mention the possibility of completely removing the Canon bayonet and replacing it with a T2 thread. That will allow you to recover a good bit of back focus. I took mine to a machine shop and was quoted $70 to have one cut on a 5axis cnc.

As for the front mounted threaded I cannot say that I would recommend that approach because the threads on the winds are glass fiber and honestly that’s the biggest disappointment for me with this wins because it almost makes it unusable With front mount filters. My b+w polarizer will not thread on properly and my hoya uv/ir cut does not seat properly either. This will make your stars completely messed up.

Your best bet will be to use a regular behind lens astro Uv/ir cut filter. If you use a bayonet adapter check out the qhy Blade, its threaded for filters up to 2” and is apparently alot better than the standard ef-ccd adapters. So far I have been paring astronomik filters with this lens, they are great with no internal reflections. After shooting multiple images with this lens, I have finally determined that the astronomik l3 does a better job on stars, you usually get 2 pixels of red chromatic abberation with this lens, the l3 almost completely prevents it and with an unmodded dslr its non existant so im sure its completely ir related. The L2 might be a safe bet, But honestly I’m nitpicking because I can open Photoshop and removing two pixels of CA is trivial even with the El but honestly I’m nitpicking because I can open Photoshop and removing two pixels of CA is trivial even with the L1.


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