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Need Help Understanding Gain settings for ZWO 2600MC

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#1 Ken101

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Posted 25 July 2021 - 02:07 PM

I just purchased a ZWO2600MC and was disappointed that the ASIAIR doesn't allow it to be used at a gain above 100.  However, in readings several posts here, the consensus seems to be that there is no reason to exceed a gain of 100.  At that point, the 2600 has almost its full dynamic range AND almost its lowest read noise.  However, aren't there cases such as imaging a dim object or imaging through a light pollution filter where I might want to use a higher gain in order to reduce the required exposure time?  What am I missing?  Thx, -ken



#2 rgsalinger

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Posted 25 July 2021 - 02:13 PM

People typically use higher gain when they are using narrow band filters. I've always thought that was because you are unlikely to exceed the smaller full well depth when using them with "normal" exposure times. So, there's no advantage in using lower gain and longer exposures - you just end up with the same SNR but need more integration time to get it. I doubt that an LP filter will limit things to the same extent, but I don't use one so, it's just a guess.

 

Personally, I prefer to just stick with one gain/offset combination and lengthen my exposures. That way I don't need multiple dark libraries and I don't have to reset my camera every time I go from NB to LRGB. I've been happy with the results, but I'll never get an APOD for my efforts. 

 

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#3 bobzeq25

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Posted 25 July 2021 - 02:14 PM

This is why people buy good mounts.  Yes, you can use higher gains than 100 to shorten exposure times.  But, you pay a price in reduced dynamic range, which hurts your images.  There's no reason to go there, unless your mount is inadequate for the longer exposures.

 

But, it's not that big a price.  If you have to do it, it's not a tragedy.

 

Note that limitations such as this are why I prefer a much more flexible general purpose computer to the ASIAir.  I'm not sure how you'd get higher gains from it.


Edited by bobzeq25, 25 July 2021 - 02:19 PM.

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#4 Jim Waters

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Posted 25 July 2021 - 02:16 PM

"there is no reason to exceed a gain of 100"  This is correct for this OSC camera.  I have an ASI2600MC Pro and I image at gain 100 and sometimes 0.  The lowest read noise is gain 100.  The best way to image faint objects is to have longer light subs.  Imaging at higher gains is sometimes done for mono narrow band filters.

 

When I plate solve in light polluted environment's I sometimes set the gain to 200.  I use NINA.


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#5 johnsoda

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Posted 25 July 2021 - 02:25 PM

I just received an ASI2600MM, and I have no plans to do data acquisition at gains higher than 100. However, there are situations where I might want to go to higher gains, especially when framing dim objects during setup. Therefore, I kind of wish that ZWO’s driver would easily allow you to do so.

 

It’s a great camera, by the way. 



#6 Jim Waters

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Posted 25 July 2021 - 02:33 PM

 However, there are situations where I might want to go to higher gains, especially when framing dim objects during setup. Therefore, I kind of wish that ZWO’s driver would easily allow you to do so.

Switch to NINA and use the native ZWO driver.



#7 Ken101

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Posted 25 July 2021 - 03:07 PM

This is why people buy good mounts.  Yes, you can use higher gains than 100 to shorten exposure times.  But, you pay a price in reduced dynamic range, which hurts your images.  There's no reason to go there, unless your mount is inadequate for the longer exposures.

 

But, it's not that big a price.  If you have to do it, it's not a tragedy.

 

Note that limitations such as this are why I prefer a much more flexible general purpose computer to the ASIAir.  I'm not sure how you'd get higher gains from it.

I understand that if my gain is high and I'm imaging a bright target, I may could exceed the full well depth of the sensor and, consequently, operating at a lower gain that results in high dynamic range is preferable.  But aren't there circumstances were even a long exposure at a higher gain will not saturate the sensor and, consequently, there will be no loss in image quality due to reduced dynamic range?



#8 Ken101

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Posted 25 July 2021 - 03:19 PM

Switch to NINA and use the native ZWO driver.

I considered switching from the ASIAIR platform to unlock the higher gains in the 2600.  (The ASIAIR, BTW, allows the use of higher gains on all cameras EXCEPT the 2600, I believe.  I know it allows much higher with the 533, for example.  I have no idea why the placed such a limitation on the 2600.)  The reason I'm hesitant to switch from the ASIAIR is that it's so comprehensive and easy to use: polar alignment, mount control, go-to, automated capture sequences, etc.  Does NINA do all that?  I'm not familiar with NINA's capabilities.



#9 bobzeq25

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Posted 25 July 2021 - 04:02 PM

I understand that if my gain is high and I'm imaging a bright target, I may could exceed the full well depth of the sensor and, consequently, operating at a lower gain that results in high dynamic range is preferable.  But aren't there circumstances were even a long exposure at a higher gain will not saturate the sensor and, consequently, there will be no loss in image quality due to reduced dynamic range?

Astrophotography targets are almost always HDR targets.  Some moreso than others of course.  Sure, you can lower the exposure enough to avoid saturating "too much".  But the dynamic range available is the dynamic range available.  <smile>

 

I considered switching from the ASIAIR platform to unlock the higher gains in the 2600.  (The ASIAIR, BTW, allows the use of higher gains on all cameras EXCEPT the 2600, I believe.  I know it allows much higher with the 533, for example.  I have no idea why the placed such a limitation on the 2600.)  The reason I'm hesitant to switch from the ASIAIR is that it's so comprehensive and easy to use: polar alignment, mount control, go-to, automated capture sequences, etc.  Does NINA do all that?  I'm not familiar with NINA's capabilities.

There are many alternatives that are _more_ comprehensive than an ASIAir.  I use Voyager, one such alternative.  It's about as comprehensive as it gets.

 

https://software.starkeeper.it/

 

Where the ASIAir shines is ease of use.  That comes at the price of limited hardware compatibility and of flexibility.

 

NINA is intermediate between Voyager and the ASIAir in terms of capability and ease of use.  Like any Windows based alternative, it's top drawer with regard to equipment compatability.  ASCOM devices are ubiquitous. 

 

Just 3 alternatives (there are more) with different virtues and drawbacks.   Just a personal choice, not right/wrong.  I'm not saying the ASIAir is bad, just that the limitations are not for me.
 


Edited by bobzeq25, 25 July 2021 - 04:04 PM.


#10 Ken101

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Posted 25 July 2021 - 07:39 PM

Thanks, everyone, for the help and suggestions.


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#11 TelescopeGreg

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Posted 26 July 2021 - 12:19 AM

I use high gain (300) all the time - for focusing.  Not everyone has an electronic focuser, and the higher gain means shorter exposures in order to get a Bahtinov pattern to show up reliably.  I've also done some imaging at 150 with a filter.  I'm pushing my mount for all it's worth (and then some) with 5 minute exposures; going beyond that because of the filter just wasn't working out.

 

If you already have the ASIair hardware and "need" the higher gain settings, consider putting Astroberry on it.  One can set the gain to anything they'd like to use.




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