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zenithstar 61 distortion

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#1 Laurent13009

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Posted 05 July 2022 - 08:15 AM

Hope I'm the right place for this....

 

I recently upgraded my setup with a sony A7 III and I now get an insane amount of distortion around the rim of frame with was never the case with my old cropped Nikon. 

 

I do have a field flattener but it seems like it can't keep up with the sensor's size. Anyone have any idea on how to fix this ? An example is attached.

 

Many thanks

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  • First_Process.jpg

Edited by Laurent13009, 05 July 2022 - 08:30 AM.


#2 Jim R

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Posted 05 July 2022 - 08:20 AM

don't see an attachment. Please edit.

#3 hornjs

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Posted 05 July 2022 - 09:30 AM

Looks like classic pattern for backspacing that is too close (all stars radiate toward the center).  If you move the sensor away from the telescope that should help.  

 

Look at post #2 in this thread...

https://www.cloudyni...cer-and-1600mm/


Edited by hornjs, 05 July 2022 - 09:31 AM.


#4 matt_astro_tx

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Posted 05 July 2022 - 09:31 AM

You'll want to post astrophotography topics in the Beginning Astrophotography forum.  But don't worry, a moderator should come along and move this thread for you.

 

Regarding your distortion, you need to adjust your backspacing outward.  You are too close.

 

Here's a decent guide on the subject.  https://optcorp.com/...rect-back-focus



#5 Laurent13009

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Posted 05 July 2022 - 10:27 AM

Thanks for the quick replies!

 

looks like I'm missing a good 15mm to reach 55mm so I guess I need extenders.



#6 EasyQuest

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Posted 05 July 2022 - 02:41 PM

Thanks for the quick replies!

 

looks like I'm missing a good 15mm to reach 55mm so I guess I need extenders.

Please check with William Optics website

 

https://williamoptic...-flat61-for-z61

 

Full frame is going to push the Field Flattener and scope ot the limits, expect not perfect corners even with proper back spacing.


Edited by EasyQuest, 05 July 2022 - 02:42 PM.



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