Amp Glow Problem using SharpCap

[eseavey]

About a month ago I did a multi night imaging session, and captured a bunch of galaxies with my QHY224C camera. The first night I imaged with Firecapture. The two following nights, I imaged using SharCap. After I got back home, I made set of darks using the two programs with the same settings as I imaged. For some reason, the SharpCap images that I stack and stretch, still have a lot of ampglow, where the images from firecapture do not. Of course I make sharpcap darks for the sharpcap images, and firecapture darks for the firecapture images. I also made sure that the Sharpcap versions for the darks and lights were the same.

I have not been able to make darks in SharpCap that removes the ampglow properly like Firecapture does. Does Sharpcap possibly do any processing to the images that would cause the darks not to work? Firecapture uses a 64bit dll where Sharpcap uses a 32bit dll, though I would be surprised if that would make a difference.

Any help what I could try would be greatly appreciated. I am at a loss and have so many great galaxy captures that I want to process.

Thanks

[admin]

Hi,

it ought to work providing that you take both the darks and lights in SharpCap at the same

* Exposure
* Gain
* Temperature (as far as possible)
* Bit Depth
* Offset

SharpCap does scale up the value of pixels if you are in the 12 bit mode of your camera - it multiplies the value by 16 for each pixel to use the full 16 bit range. This is not a problem as long as both the dark and the light frames are treated in the same way. (Note that in SharpCap 3.1 you can turn this scaling off for FITS files in the settings - set the option 'Save 10/12/14 bit images in FITS files without stretching' - make sure you use this for both darks and lights if you choose to use it).

If you still have issues then please share a dark and a light frame.

thanks,

Robin

[eseavey]

Thanks Robin,
I attached the camera settings as I was not able to upload the fits files. The one with the higher cooling power was the image file, and the other is the dark. I put my camera in the refrigerator when taking darks, and I guess the fridge was colder than the temperatures when I was imaging.

I think the settings were the same for the rest. Did I miss anything?

[admin]

Hi,

the settings look fine. I'm afraid that large files will need to be uploaded to some sort of file sharing web site (dropbox, google drive, etc) and then put a link here for me to download them - I have a limit on attachment size just to keep the amount of data that needs backing up manageable.

One thing I have noticed in the past is that if you are using PixInsight then beware of the 'Optimize' option in dark subtraction - it may work under some cases but in others it makes a right mess of things and basically the dark doesn't subtract well at all.

cheers,

Robin

[eseavey]

Maybe this is good news, and a response in combination to a recent threat I started regarding sensor analysis and settings. I did a test setup couple days ago and shot a couple of subjects using the recommended settings for max dynamic range and noise less that 1%. Sharpcap recommended about 60s exposures at gain=5. I shot 10 lights and 5 darks with these settings, and processed the image. Interestingly, I am not seeing the ampglow, and even using a line profile analysis in ImagesPlus, I am not seeing the terrible ampglow. I also turned off the Sharpcap stretching to 16bit.

(I know the shot is a bit grainy, it was a test to see if I still have ampglow with these settings. Normally I take about 100 subs.