Applying Dark Frames with SharpPro Live Stacking

Discussion of using SharpCap for Deep Sky Imaging
jsadoulet
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Re: Applying Dark Frames with SharpPro Live Stacking

#11

Post by jsadoulet »

Hello Robin
I hope Covid is not impacting too much in your location...

Camera ZWO 294 MC Pro and SharpCap

Please confirm the following:
1/ When creating darks with SharpCap, they are not debayered and saved in "gray" format ?
2/ When using darks with SharpCap livestacking, you use "gray" format as well even with a color camera ?
3/ If I want to use darks in an external sofware (PI) with RGB images, I need to convert my darks in RGB ?

Thank you for your answer

Jean-Paul
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Re: Applying Dark Frames with SharpPro Live Stacking

#12

Post by admin »

Hi Jean-Paul,

When you are using a colour camera, dark frames are saved in raw format (grey image with Bayer pattern visible) and used in that format, this includes individual dark frames and averaged dark frames.

I'm not a great pixinsight expert, but I would expect that you would want to use the dark frames in pixinsight without converting them to RGB. You want to subtract the dark signal at the pixel level before doing the RGB conversion to make sure that the subtraction is as accurate as possible.

COVID-19 is of course stopping us from carrying out our normal day-to-day lives to some extent – we can only go out to buy food and for one period of exercise per day. I think there are relatively few cases nearby so far – at least compared to places like London. I hope that you and all other forum members and SharpCap users keep safe and well during this crisis.

Cheers, Robin
celvii
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Joined: Sat Jul 11, 2020 8:11 pm

Re: Applying Dark Frames with SharpPro Live Stacking

#13

Post by celvii »

I have recently decided to build a dark frame library so I can experiment with exposures and not have to sit there building dark frames all night.

While working with my library and reviewing the dark frame stacks Sharp Cap has saved in the past, I noticed that Sharp Cap auto saved some in png format and some in tiff format. Those old files do not have the associated camera settings txt files so I could not research why the different format saves, and don't remember what I might have selected for the output format.

I looked at the new/recent dark frame stack camera setting txt files and noticed that no matter what format the dark frame was saved in (png, tiff, fits) the txt file recorded the same info: Output Format=FITS files (*.fits). I noticed while capturing the dark frame stack with the Sharp Cap Capture Dark feature, the Output Format setting in camera controls changes to FITS, no matter what I manually set it to, and then back to the manual selection upon completion of the capture.

In the Sharp Cap manual it states that Sharp Cap live stacking will not read 16bit info from a dark frame stack png file. It will from tiff or fits.

My parameters: Using Sharp Cap Pro 4.0.8418.0, ZWO ASI2600MC Pro, capturing in RAW16, 6248x4176, and generally saving live stacks in png 8bit. I currently use the png 16bit save for further processing in Pixinsight or Photoshop, and am experimenting with the RAW auto save feature in live stacking (tiff) for traditional stacking in other software.

So my questions are:
1). Does it matter what format I save the Dark Frame Stack in for use in Sharp Cap live stacking?
2). Does it matter what format I save Dark Frames (not stacks) in to use in stacking software? In other words do I need png dark frames to use with png captures?
MikeHuerto
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Joined: Thu Jan 21, 2021 12:05 pm
Location: Spain

Re: Applying Dark Frames with SharpPro Live Stacking

#14

Post by MikeHuerto »

Hi Robin

I just tried using a Sharpcap master dark to remove amp glow from 30 lights I captured last night (pointing the camera folder at the light folder, and the pre-processing folder, at the Sharp cap master dark. The master dark was created immediately after capturing the lights, with exactly the same settings as lights. I was surprised to see that it made the amp glow worse - instead of removing it I played with various settings in processing, but to no avail. Any advice, is there a reason that you recommend DSS for this? Camera as the ASI294MC pro at -15 C 3 min subs at 130 gain.

Mike
Bortle 5
Skywatcher GOTO Synscan 14" Dobson
Skywatcher 130PDS on HEQ5
ZWOASI224MC and ASI294MCPro
Laptop = Lenovo Legion 5 FullHD 144Hz (Intel Core i7-10750H, 16GB RAM, 512GB SSD, NVIDIA RTX2060-6GB, Windows 10
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Re: Applying Dark Frames with SharpPro Live Stacking

#15

Post by admin »

Hi Mike,

what processing software were you using? If it is PixInsight, make sure you turn off 'dark frame optimization' - I have heard that option being turned on seemed to stop subtraction from working properly when using darks that have visible amp glow.

cheers,

Robin
MikeHuerto
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Re: Applying Dark Frames with SharpPro Live Stacking

#16

Post by MikeHuerto »

Hi Robin,

Sorry if I was not clear I was using Sharpcap as my processing software. In otherwords, I first selected the light frames in the Camera Folder, then selected the master dark (made in SC) in the preprocessing tool. I then Livestacked, -thats where I could see that the amp glow as considerably worse - even after the first few frames

Without the dark frame master, the restacking of the lIghtframes using the Livestacking tool works fine - except for the amp glow. Its just when I add the master dark frame (made in SC)that I see it makes the amp glow much worse. Again, ALL settings for dark and lights were the same - except the darks were done with the lens cap on with dark cloth over the camera - at night - immediately after I took the lights.

Mike
Bortle 5
Skywatcher GOTO Synscan 14" Dobson
Skywatcher 130PDS on HEQ5
ZWOASI224MC and ASI294MCPro
Laptop = Lenovo Legion 5 FullHD 144Hz (Intel Core i7-10750H, 16GB RAM, 512GB SSD, NVIDIA RTX2060-6GB, Windows 10
MikeHuerto
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Location: Spain

Re: Applying Dark Frames with SharpPro Live Stacking

#17

Post by MikeHuerto »

OMG - :roll: :roll: :roll: please ignore - I just reviewed the settings file for the master dark - somehow gain got reset to 390 from 130 , as was used for the lights. No idea how that happened! Embarrassing !! Well it was 3 in the morning. !!! So basically, the dark is overcompensating for the amp glow.

Sorry to bother you. I will redo the darks!!

Great software!!!

Mike

PS.I use Startools to process the final FITS file generated by SC Livestack, but I find that SC acts as a quick test that stacking and calibration is approximately OK.

EDIT: Yep - it worked - the new dark frame removed all the amp glow!
Bortle 5
Skywatcher GOTO Synscan 14" Dobson
Skywatcher 130PDS on HEQ5
ZWOASI224MC and ASI294MCPro
Laptop = Lenovo Legion 5 FullHD 144Hz (Intel Core i7-10750H, 16GB RAM, 512GB SSD, NVIDIA RTX2060-6GB, Windows 10
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