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INDI Library v1.9.9 Released (30 Nov 2022)

Bi-monthly INDI Library released with new drivers and bug fixes.

Darks, Flats and bias frames

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As I have become a bit more comfortable with my asrtoberry setup and using kstars/ekos I would like to start taking additional frames to hopefully help with my stacking.  I was already taking dark frames, but I guess I want to check if I am doing all this right.

For dark frames I cover my scope and take 20 or so frames at the same conditions as the subs  I took.  I then drop all of those frames into DSS with my light subs and stack.
Flats confuse me still.  I covered my telescope with some white cloth and tried to get even lighting (have a light on the way) and used the calibration wizard or whatever in ekos.  I just selected Flats > dust cap with light > and then number of frames I wanted.
I am lost on the difference between bias and darks.

So my questions are what are bias frames and how do you take them? For flats do I need to do any post processing or does it work just like darks and I throw them all into dss for it to make a master flat file (do I need to do any histogram editing or anything first)?  I want to figure this out because the biggest issue I have with my pictures now is vignetting and then gradient circle stemming out from the center ( I assume this may be light pollution).
 
Celestron Nexstar 6se (az only)
ZWO ASI 533MC pro
Hyperstar
Pi running astroberry
9 months 1 week ago #80968

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Replied by Paul on topic Darks, Flats and bias frames

John,
Bias is part of every image you take.
So, it is part of a light, dark and flat image.
Whenever you take a dark away from a light or flat image you are also removing the bias because it is part of the dark.
You can however create a master bias image by taking the shortest exposure your camera will take in the dark tto create a bias frame, and stack multiple for a master bias. You can then include it in your processing workflow.
Although some people do this, it is not necessary unless you are taking darks with a different exposure length to your original images.
Paul
Losmandy G11 with Gemini 2 controller
QSI 583/683 monochrome cameras with filter wheel
Starlight Xpress Lodestar X2 guide camera
Microtouch Focuser controlled using Arduino UNO emulating Feathertouch controller
Raspberry Pi 2GB with Raspberry Pi OS 64bit Bullseye
The following user(s) said Thank You: John
Last edit: 9 months 1 week ago by Paul. Reason: spelling
9 months 1 week ago #80981

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Replied by John on topic Darks, Flats and bias frames

Thanks. As far as flats go is there anything special I need to do? Do I just select flats in the drop down list click calibrate and do I pick a number on the right hand side or do I let it do auto? Then after that do I need to do anything special with those flats or just put them in dss to stack and make a master?
Celestron Nexstar 6se (az only)
ZWO ASI 533MC pro
Hyperstar
Pi running astroberry
9 months 1 week ago #81006

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  • Thank you received: 27

Replied by Paul on topic Darks, Flats and bias frames

John,

I have tried the auto setting but found that it would change exposure times during a flats run so I now always determine the setting I want for each filter and program the sequences in as I would capturing images. After the flats I do a series of darks for each of the flats.
I then create a master flat for each filter using ASTAP and process my images.
Paul
Losmandy G11 with Gemini 2 controller
QSI 583/683 monochrome cameras with filter wheel
Starlight Xpress Lodestar X2 guide camera
Microtouch Focuser controlled using Arduino UNO emulating Feathertouch controller
Raspberry Pi 2GB with Raspberry Pi OS 64bit Bullseye
9 months 2 days ago #81167

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