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Any ideas why reducing camera gain in APT makes displayed image brighter?


Demon
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On the ASI178mm I'm taking images, however reducing gain gradually below 100 seams to make image brighter...

Increasing above 100 gain its working right and images get brighter but reducing should always go dimmer - does not make sense to me.

All at same exposure time.

When I swap to Sharpcap it operates correctly, but I generally operate rig from APT so would like to get to bottom of this.

Are there any auto functions in APT? etc?...cant see any so far...

When in apt live view the settings I am using are completely different also to get similar images on the display.

Think something is tweaking them...

Any suggestions greatly appreciated thanks.

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Thanks Terry, I read there is a setting burried away in apt that disables the gain values in apt and let's the camera decide - surprised I thought it changed the image but maybe just conditions changing. Will open obsy later and see if that option is set. Much appreciated.

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Sadly I had the setting correct - APT was controlling gain - so I'm still stuffed...

Any ideas greatly appreciated.

Was going to try for Whirlpool Galaxy tonight but may have to try out Sharpcap...

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Gutted, got on the Whirlpool - can easily see the beautiful spiral arms in live view but images are pants - very frustrating...

I ended up recording an ser in sharpcap which was even more frustrating. The images with sharpcap compared to apt with the same settings are so different and neither are really what I should be getting. Just need some control of them - think a reinstall of apt is next...

Edited by Demon
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Something else you could try is the ZWO ASI Studio software https://dl.zwoastro.com/software?app=ASIStudio&platform=windows64&region=Overseas or https://dl.zwoastro.com/software?app=ASIStudio&platform=windows86&region=Overseas.

Then use the ZWO driver https://dl.zwoastro.com/software?app=AsiCameraDriver&platform=windows86&region=Overseas rather than ASCOM. That may reveal whether the issue is with the ZWO driver or ASCOM driver.

 

Most people prefer to use the ASCOM driver and entire ASCOM package BTW.

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I think Terry is on the right track and this is to do with the way APT is stretching the pre-view of the image.

 

I have just done a quick check with some darks from my QHY163m. If I have the APT histogram set to Auto-str l and open a gain 0 and gain 150 image (same duration) the Gain 0 show as MUCH brighter on the screen. but if i look at the histogram peak, the gain 0 is closer to left side than the peak of gain 150.Also, the Range showing on the G0 is 140 - 53837 while on the Gain 150 it goes up to 100 - 65504. Both of these mean the Gain 0 IS darker than the G 150 but the stretche G0 is MUCH Brighter than the G150. Its to do, i think with how the autostretch is being applied - not on the brightness of the actual image.

 

Honestly I dont put much value on how the image looks within APT - they always look rubbish!

 

Unless I am misunderstanding and its your final images, not the preview images in APT that are  wrong.

Edited by Dmack1
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Thanks Guys, Your life savers, my heads fried in the heat and so many late nights in a row. I'll give them a go thanks very much. I have been going off the preview and if its just the preview being stretched which sounds right and your tests confirm then it makes sense. I need to use the histogram and I'll definitely try the zwo software as you say and have a look at the actual images away from apt. Sounds like as you say I just need to think a little differently and leave till Dss and postprocessing. Fingers crossed.

I'm gutted as I had the whirlpool full frame, really good seeing and everything was working really well - also while wearing t shirt and shorts outside - bizarre...

Greately appreciated, thanks.

 

Edited by Demon
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