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Error when using a Master BIAS file with lights of 0 Gain  

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(@stastro)
White Dwarf Customer
Joined: 1 year ago
Posts: 16
September 14, 2020 12:35  

I am currently testing an ASI2400, when using Gain 26 everything works great, however when using Gain 0 things do not go according to plan

When using a Master BIAS that was created using APP, when assigning masters to the light frames and attempting to perform an integration or preview as "l-calibrated" the following exception gets thrown

Encountered error in module:
LightFrameCalibration

Error message:
java.lang.ArrayIndexOutOfBoundsException: 1

Cause:
1
dK.a(Unknown Source)
dK.doInBackground(Unknown Source)
javax.swing.SwingWorker$1.call(SwingWorker.java:295)
java.util.concurrent.FutureTask.run(FutureTask.java:266)

 

I have also noticed that when using a Master Dark with a Gain of 0, it causes my calibrated images to look like they have had flats super exposed on them, I have verified that it is the darks because if I use a dark of gain 26 the issue does not appear on the calibrated images.

 

For the master BIAS at Gain 0, I have re-created BIAS frames and master and same result, does not happen when I use a Master BIAS at Gain 26

 

This topic was modified 1 month ago by Simon Todd

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(@stastro)
White Dwarf Customer
Joined: 1 year ago
Posts: 16
September 14, 2020 13:49  

The Exception is thrown only when the light frames are GAIN 0 and there is a Master BIAS present (No matter what the gain value)


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(@vincent-mod)
Quasar Admin
Joined: 3 years ago
Posts: 2469
September 15, 2020 09:53  

Yes, a gain of 0 is probably not what you want. Keep the settings the same as you regular exposures, but take bias frames at about 0.05 second exposures etc.


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(@wvreeven)
Neutron Star Customer
Joined: 2 years ago
Posts: 243
September 15, 2020 10:19  

If I look at the diagrams of this camera

then I'd say that a Gain of 0 is perfectly viable. Either that or Gain 140 would be my choice. So I would say that there either is something wrong with the images taken at Gain 0 or there is a bug in APP. What software were the images taken with? And what version of the ZWO drivers does it use?

Since this is one of the modern CMOS cameras, I repeat my advice (which I apply myself with my ASI1600, ASI2600 and ASI6200 cameras to, if I may say so myself, great success): do not take bias frames. Instead, take darks and dark flats and use those to process your images. For my ASI2600 and ASI6200 I use either Gain 0 or Gain 100, since the drop in read noise occurs at that Gain for these cameras.

 

HTH, Wouter


(@vincent-mod)
Quasar Admin
Joined: 3 years ago
Posts: 2469
September 15, 2020 10:38  

Mmm, interesting. I misread the part where you take the light frames at gain 0 in combination with a gain 0 of the calibration files. It would be interesting to have a look at those master calibration files and a few light frames for me to see if it indeed triggers an exception and if this is to be expected or indeed a bug.

Go to https://upload.astropixelprocessor.com and use upload1 (or upload2 till 5) as username and password will then be the same as the username.

Create a directory named “stastro-gainzero” and upload in there. Thank you!


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(@stastro)
White Dwarf Customer
Joined: 1 year ago
Posts: 16
September 15, 2020 16:11  

Just uploaded

 

Master Dark - Gain 0

Master Bias - Gain 0

Master Flat - Gain 0

8x Light frames at Gain 0

 

Simply load them all up, assign masters to lights then either view the calibrated image, or perform an integration and you will hit the exception


(@vincent-mod)
Quasar Admin
Joined: 3 years ago
Posts: 2469
September 15, 2020 17:16  

Superb, thanks a lot!


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(@stastro)
White Dwarf Customer
Joined: 1 year ago
Posts: 16
September 16, 2020 10:41  
Posted by: @wvreeven

If I look at the diagrams of this camera

then I'd say that a Gain of 0 is perfectly viable. Either that or Gain 140 would be my choice. So I would say that there either is something wrong with the images taken at Gain 0 or there is a bug in APP. What software were the images taken with? And what version of the ZWO drivers does it use?

Since this is one of the modern CMOS cameras, I repeat my advice (which I apply myself with my ASI1600, ASI2600 and ASI6200 cameras to, if I may say so myself, great success): do not take bias frames. Instead, take darks and dark flats and use those to process your images. For my ASI2600 and ASI6200 I use either Gain 0 or Gain 100, since the drop in read noise occurs at that Gain for these cameras.

 

HTH, Wouter

Whole point of Gain 0 is to utilise the 100k full well capacity, going to 140 gain would drop the full well down to around 20k which would then lead to star saturation and loss of colour, I intentionally use Gain 0 for bright broadband targets, and gain 26 for L-eXtreme NB targets as well as darker broadband targets.  I plan on getting the 6200 shortly.

Frames were captured with SGPro


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(@wvreeven)
Neutron Star Customer
Joined: 2 years ago
Posts: 243
September 16, 2020 12:20  
Posted by: @stastro

Whole point of Gain 0 is to utilise the 100k full well capacity, going to 140 gain would drop the full well down to around 20k which would then lead to star saturation and loss of colour, I intentionally use Gain 0 for bright broadband targets, and gain 26 for L-eXtreme NB targets as well as darker broadband targets.  I plan on getting the 6200 shortly.

Frames were captured with SGPro

Of course you are right. My point wasn't to not use Gain 0 but to not use bias frames 🙂

 

Wouter


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(@stastro)
White Dwarf Customer
Joined: 1 year ago
Posts: 16
September 16, 2020 12:40  
Posted by: @wvreeven
Posted by: @stastro

Whole point of Gain 0 is to utilise the 100k full well capacity, going to 140 gain would drop the full well down to around 20k which would then lead to star saturation and loss of colour, I intentionally use Gain 0 for bright broadband targets, and gain 26 for L-eXtreme NB targets as well as darker broadband targets.  I plan on getting the 6200 shortly.

Frames were captured with SGPro

Of course you are right. My point wasn't to not use Gain 0 but to not use bias frames 🙂

 

Wouter

I was wondering about using BIAS frames myself, as it would appear that Flats Calibration uses the BIAS frames data to subtract from the flats, when calibrating light frames, the BIAS data would be subtracted when the darks get applied, so maybe I just do that

1. Create Master Flat with Master BIAS subtracted

2. Calibrate Lights against Master Flat and Master Dark (Master Dark contains BIAS)

Then there would be no need to load up a Master BIAS at all and assign it to light frames.  But then will also wait for @vincent-mod to investigate why the exception gets thrown too

 


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(@vincent-mod)
Quasar Admin
Joined: 3 years ago
Posts: 2469
September 17, 2020 14:24  

That's a good idea @stastro, your darks will have bias in them as well so that can be used and they won't have an issue as darks are longer exposed anyway. Bias I think can be used still, just increase the exposure to say 0.05-0.1 seconds. But the way you suggest should work fine as well.

I'll download the data asap and have a look as well.


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(@vincent-mod)
Quasar Admin
Joined: 3 years ago
Posts: 2469
September 20, 2020 12:08  

Hey, so I get the exception as well for the masterdark. I'll ask Mabula to see if this makes sense or not.


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(@stastro)
White Dwarf Customer
Joined: 1 year ago
Posts: 16
September 20, 2020 14:53  

@vincent-mod

At least I am not going mad 😀


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(@vincent-mod)
Quasar Admin
Joined: 3 years ago
Posts: 2469
September 21, 2020 16:07  

Yep, I'm discussing it with Mabula and he mentions it should just work. So it's either an issue with the dark itself or a bug, we're going to look into it.


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(@stastro)
White Dwarf Customer
Joined: 1 year ago
Posts: 16
September 21, 2020 21:45  
Posted by: @vincent-mod

Yep, I'm discussing it with Mabula and he mentions it should just work. So it's either an issue with the dark itself or a bug, we're going to look into it.

Just so happens that I tried with a Gain26 MasterBIAS today and it threw the same exception, so it is nothing to do with the GAIN 0, and it only happens when there's a MasterBIAS loaded with the lights, without the MasterBIAS it works fine, so maybe there should be a check in the "Assigning masters to lights" that prompts the user "Have your Master Flat(s) been calibrated against master BIAS" and if the user selects "Yes" then is de-selects the MasterBIAS and allows the calibration / integration to go through without an error

 


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