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Rokinon 135MM wide field targets

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#1 Swordfishy

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Posted 24 February 2020 - 12:04 PM

Hey all,

 

 Here is what I was able to do with the Rokinon 135 @ F2.8 and Sony A7. Star Adventurer star tracker.

 

 I love the lens, it is great for the price, I mean superb. I have issues with focus due to the flange distance for the Sony A7 and the adapter I am using, I end up having to shimmy it with aluminum foil and thus it is very difficult to reach focus. Still I am quite happy with the results. This was a fairly dark sky. 

 

 Processed in Pixinsight. Darks and flats.

 

 

Full Resolution here.   https://www.flickr.c.../183884205@N03/

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#2 Swordfishy

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Posted 24 February 2020 - 12:05 PM

A few more. given the size limit.

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#3 fishonkevin

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Posted 24 February 2020 - 12:51 PM

Try the Southern Auriga region.


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#4 Swordfishy

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Posted 24 February 2020 - 12:57 PM

Try the Southern Auriga region.

Looking at the SA GTI mount... Go to that runs on AA batteries... Then Ill be in business...



#5 calypsob

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Posted 28 February 2020 - 11:20 AM

Nice job what adapter do you have? Why did you stop the lens down?
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#6 Swordfishy

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Posted 28 February 2020 - 01:04 PM

Nice job what adapter do you have? Why did you stop the lens down?

I am using the Fotodiox M43 - NEX adapter. It has a LOT of play... Therefore I shimmied it best as I could to try and achieve infinity focus, I am LITERALLY on the razor's edge with it... At F2, I can't really focus perfectly, comes close, but not perfect... Thus I stopped it over twice to F2.8 and I am pleased with the result. 

 

 I shimmied it using Aluminum paper, to get the lens closer to the sensor. I also adjusted the infinity focus on the lens, but even then, it is only so far. I bought a bathinov mask printed specifically for it and do my best to twist it as far as possible. 

 

 In hindsight, shouldve just bought the Sony E mount version, but again, this one was a good deal and the results arent the worst. F2.8 is STILL beastly fast :-)

 

  I will try to put it together with my ASI 183MM and filter wheel and see if I can reach infinity with that... I got the adapter for that as well. Now just need to figure out how to use it with a rigel n step, how to mount the motor and use a belt etc... Then ill be in business... IF I can get infinity focus with the dedicated. I reprocessed some of the images, they are down in the link. Rossette especially looks a lot more defined.

 

 

 https://www.flickr.c.../183884205@N03/



#7 Kevin_A

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Posted 29 February 2020 - 03:19 PM

Have you tried focusing with a narrow slot Bahtinov Mask..... i use mine at F2.0 but need the mask to focus it.


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#8 Swordfishy

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Posted 01 March 2020 - 09:23 PM

Have you tried focusing with a narrow slot Bahtinov Mask..... i use mine at F2.0 but need the mask to focus it.

Yep. I just can't reach infinity focus. I'm going to sell the lens and buy it again but with the correct e mount so I can foregoo adapter.



#9 neighborhoodastro

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Posted 03 March 2020 - 03:55 PM

With 135mm you could do Heart Nebula + Double Cluster I'm pretty sure


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#10 Swordfishy

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Posted 04 March 2020 - 10:04 AM

With 135mm you could do Heart Nebula + Double Cluster I'm pretty sure

Its very wide. I put it up for sale since I want native E-mount. If I could reach infinity I would have kept it happily since it is a superb piece of glass.



#11 calypsob

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Posted 04 March 2020 - 11:49 PM

Its very wide. I put it up for sale since I want native E-mount. If I could reach infinity I would have kept it happily since it is a superb piece of glass.

Well you may want to just get a good adapter like a sigma mc11. Im not sure what adapter I have, its chinese, but lets me hit infinity with the a7rIII


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#12 Swordfishy

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Posted 05 March 2020 - 10:23 AM

Well you may want to just get a good adapter like a sigma mc11. Im not sure what adapter I have, its chinese, but lets me hit infinity with the a7rIII

Been looking and no luck. I am using the cheap Fotodiox and because its so loose I have to shimmy it into place for it to be flat... 

 

 Now, I just looked at the MC11 adapter and it seems like the sensor would be even further from the glass, which is the issue now. Am I incorrect? I would rather spend $100 on a great adapter that will solve both my issues than go the selling and rebuying route, especially since I have not gotten any interest in the lens yet. 

 

 I do have an adapter for the ZWO camera so it wont be a waste if it dont sell, though I am not sure if I can reach infinity focus there, gotta try it.

 

 Thank you for answering! The Sonys are amazing, just need the software to be like everyone else so we can use them properly with dedicated acquisition platforms.




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