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Cannot Achieve Focus with ZWO cam and Roki/Samyang 14mm F2.8

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#1 SpaceManSam

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Posted 01 March 2021 - 11:39 PM

Hello, Im wondering what I can do to achieve focus with my ZWO 294MC Pro,Rokinon 14mm f2.8 lens, and the ZWO to EOS T2-II Adapter. I can't seem to achieve the correct spacing and Im finding that moving the sensor closer to the lens gets me closer to optimal focus but theres physically no way of doing that. I would still have to remove a few millimeters if I wanted to achieve focus but as stated before. I currently have zero solutions of accomplishing this. Any suggestions or prior experiences shared would be greatly appreciated! Thanks for reading!~ Sam.



#2 t-ara-fan

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Posted 03 March 2021 - 02:06 AM

Not a refractor question, but I will allow it lol.gif

 

The ZWO to EOS T2-II Adapter comes with a 5mm long extender tube, which you use with cameras that have a 12.5mm backfocus.You don't need it with your camera that has a 17.5mm backfocus. Remove the 5mm long extender and report back.


Edited by t-ara-fan, 03 March 2021 - 02:07 AM.


#3 jimjim84

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Posted 15 March 2021 - 04:40 PM

I have a similar issue as @SpaceManSam

 

+ Rokinon 14mm f/2.8 Series II Lens for Canon EF

+ ZWO EOS-T2 adapter (New version and NO 5mm ext tube)

+ ZWO 183MC Pro (including 11mm T2 extender)

 

On the ZWO website for the EOS-T2 adapter, Woo Chun kit wrote in the comments on July 26, 2020 that they were able to achieve focus by putting the Rokinon at f/22.  I tried this and it did indeed seem to be focused on my target (random house object at the time). 

 

Here is their Google Translated comment:

 

I just used this adapter to connect to my samyang 14mmF2.8 (ef port) lens, but it couldn’t achieve focus. I had to close the aperture to at least F22. Then I changed to an eos to t2 adapter without a filter slot. 26.5mm, it needs to be reduced by 1mm, but I use samyang 135mmF2.0 and there is no such problem, a total of 44mm is just right (add I use 071mcpro)

 

Two side notes:

1 - I'm still very very new to anything photography.

2 - I've heard comments in other forums and webpages that some people had to go through a couple Rokinons 14mm to find one that was "center focused correctly" from the factory.




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