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OSC - R channel focusing priority?

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#1 Terata

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Posted 22 October 2021 - 03:20 AM

Capture.PNG

 

Hi, 
 
I noticed something for the first time recently with an image of the Bubble nebula with ASI533mc OSC and Sharpstar 61EDPH using the Optolong L-eXtreme filter and the ZWO EAF for autofocusing. When I split the channels it appears that R is more out of focus when compared to G and B

 

I have seen some old threads about this but none of them really offer any kind of solution. Has anyone found a smart way of focusing with priority assigned to the R channel, the channel with the stronger signal for imaging emission nebula? 

 

Br Alan

 

Integration Image with channel split, RGB in that order. 3 hrs integration time


Edited by Terata, 22 October 2021 - 03:25 AM.


#2 bulrichl

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Posted 22 October 2021 - 04:00 AM

Focusing according to the R channel will not fix the problem, then the G and B channel will be out of focus.

 

The specification of the ZWO ASI533MC says that the protect window in the camera is only an AR (anti-reflective) window. You will have to use a UV/IR cut filter additionally in order to cut off wavelengths > 700 nm.

 

Bernd


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#3 Terata

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Posted 22 October 2021 - 09:12 AM

I am using the Optolong L extreme dual band filter so unless there is leakage of other wavelengths with the filter I would have thought that adding a UV IR cut would not make a difference.
Alan

#4 imtl

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Posted 22 October 2021 - 11:40 AM

This has nothing to do with uv-ir cut. It is about the CA of your optics and the fact that you use an OSC.
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#5 bulrichl

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Posted 23 October 2021 - 04:29 AM

I am using the Optolong L extreme dual band filter so unless there is leakage of other wavelengths with the filter I would have thought that adding a UV IR cut would not make a difference.
Alan

Sorry, I missed the fact that you used a narrowband filter.

 

Bernd



#6 calypsob

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Posted 28 October 2021 - 06:56 AM

Something is off here. Red should not be that blurry. Is this the doublet version of the 61?

#7 ks__observer

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Posted 28 October 2021 - 02:16 PM

This has nothing to do with uv-ir cut. It is about the CA of your optics and the fact that you use an OSC.

+1



#8 RogeZ

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Posted 28 October 2021 - 07:59 PM

This has nothing to do with uv-ir cut. It is about the CA of your optics and the fact that you use an OSC.


Yep. This is exactly what CA does.


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