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ZWO 2600mm Question

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#1 crgood2

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Posted 13 April 2021 - 10:49 AM

Hey All,

 

Working through first light on my new 2600mm and I had a gain question; according to the diagram on ZWO's page, the HCG mode occurs at gain 100, and seems most beneficial to shoot there:

 

1.JPG

 

However, in the driver (which I downloaded just now to confirm I have the most recent one), the max gain is 100, which seems odd because I believe there should be more beyond it based on ZWO's graph:

 

2.JPG

 

Am I over thinking this?  Should Gain 100 in the driver be the 'sweet spot'?



#2 Midnight Dan

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Posted 13 April 2021 - 11:00 AM

I noticed that too on my 2600.  I can't see any reason to use gain above 100.  I'm wondering if myabe ZWO figured there was no advantage so they limited it to 100?  Might be something to ask on their website.

 

-Dan



#3 robbieg147

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Posted 13 April 2021 - 11:03 AM

If you increase the gain beyond 100 you are not gaining anything except loosing dynamic range (the blue graph), I sometimes use my 2600 at 0 gain to get the approx 1/3 of a extra stop of DR but generally just keep it at 100 to benefit from the reduced read noise.

 

Using APT I think you can set the gain to whatever you want??



#4 crgood2

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Posted 13 April 2021 - 11:11 AM

Yea I agree the 100 is ideal and you wouldn't want to go past it, I just to make sure it actually is the "HCG" mode I suppose.  I posted over at the ZWO forum too, thanks!



#5 jerahian

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Posted 13 April 2021 - 11:48 AM

I feel like the driver should have simply exposed a checkbox instead of a slider, like "[  ] HCG Mode", since you really would only want either 0 or 100 gain.  Anything in between, or anything above 100, doesn't really make sense.  The slider also confuses the issue by making it look like you may be setting a percentage, kinda like what PHD2 does (I hope this really isn't the case here).

 

Lastly, unity for this sensor is below 0 gain as it is; that's how sensitive this darned thing is!

 

Ara


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#6 Der_Pit

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Posted 14 April 2021 - 05:18 PM

Lastly, unity for this sensor is below 0 gain as it is; that's how sensitive this darned thing is!

That is though not really related, it's just a question of ADC bit depth and full well capacity.... (the FWC of the 2600 is smaller than the 65535 the ADC allows).  So it would be the same, even if the QE would only be 10%...


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#7 astromomo

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Posted 14 April 2021 - 06:08 PM

Hi,

 

I think you can use more gain, but you have to work on sharpcap for example.

 

Nimmervoll explains a lot about this camera: https://www.youtube....V9t_edq5KA&t=6s (you can switch to 9min).


Edited by astromomo, 14 April 2021 - 06:12 PM.


#8 Pete_xl

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Posted 15 April 2021 - 02:54 AM

It is possible to set higher gain values in NINA. But I see no reason to do this. The only decision IMHO is between gain 0 for optimum well depth + DR or gain 100 for optimum read noise + DR. After comparing some luminance shots gain 0 with 180s against gain 100 with 60s I will continue shooting LRGB and NB with gain 100 and vary exposure time.




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