What You Don't Know About Calibration Frames | Darks and Flats Deep Dive
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- čas přidán 8. 07. 2024
- 00:00 - Introduction
00:11 - Misconceptions around calibration frames
01:49 - What calibration frames are
02:09 - Types of calibration frames
02:59 - Dark frames
06:39 - Are dark frames really necessary?
09:58 - The problem of noise in calibration frames
14:01 - Flat frames
17:45 - The importance of ISO/Gain for Flats
20:37 - Multiplicative artifacts
21:39 - Flat calibrating an image
22:34 - Bias & Dark Flats
25:00 - Summary
25:22 - Tips for taking calibration frames
26:43 - Conclusion
How to take manually exposed flat frames: nightskypix.com/calibration-f... - Věda a technologie
This is the clearest and best presented explanation of calibration frames I have seen. A lot of materials found on forums are just recipes (good and bad) presented either without reason or with faulty reasoning. Thank you SK.
@@Birko64 thank you for saying this! I agree so many people just tell you what to do without any context!
Thanks for the well thought out explanation. I have watched many calibration videos over the past 4 yrs. But your teaching skills are much better than most. Clear skies
Wow that’s such a nice thing to say, thank you! CS
Thank you for making this video. It is the best explanation of calibration frames I have seen on CZcams so far.
@@CosmicCaptures thank you so much I’m glad it’s helpful!
Great tutorial. Thanks for that. I'am among the lazy fraction of astrofotographers, who try to restrict the calibration work to the indispensable minimum, which really matters in the final picture. Flats are indeed indispensable, specifically for fast optics, the other depend on the camera and the ambition for the final picture. You have supplemented what I exercise after long experimental experience with solid scientific justifications.
I’m glad we’re in the same page ☺️ I can relate - I am all about optimizing! I’d never skip my flats though 😁 clear skies!
Excellent explanation! I’ve heard this articulated before but your scale analogy is perfect
Thank you! It took me forever to come up with something that is easy to grasp! 😁
Excellent discussion of the needed exposure time for flat frames. I had the striping problem you described but didn't know the cause. Experimentation with neutral density filters between my light panel and telescope solved the problem by lengthening my exposure times. But until I saw your video, I didn't know why very short flat frame exposures were causing the problem. Well done!
Thank you! I just put sheets of paper in between when I have to take flats with a fast scope! 😁
This is, I believe, the first video I have seen of yours. I like your rice and plate algorithm. You are clearly smart and thorough. I think I'll be watching more.
that's very nice of you to say, thanks for being here!
What a crazy good explanation on these concepts, thank you!
@@Photo-Jay thank you so much! I’m so happy people appreciate the deep dive approach ☺️
I'm glad you started making these longer videos to explain things.
How do you build up a library of master darks? Don't they have to be taken every time? I missed something, I think. I'll watch the video again.
Also, if you every feel like making a video explaining proper ISO/gain settings for DSO imagining, I don't think I'd be the only person who would greatly appreciate that.
Darks can be reused over and over! The only one that’s session specific is the flat. For the dark library you just take them for each temperature you want to shoot at - in case of a cooled camera. For a non-cooled camera you’ll still do the same but as you can’t control the temperature you try to take them at each 5-degree increment as the weather allows and then later use the one that is closest to the current temperature. I have been known to take darks in my fridge for the fall-winter 😁😁
@@the_space_koala Thank you.
Great job! You don’t just clobber us with knowledge, but back up and justify your views. Very clear explanation.
One thing I would like to hear your opinion on is dark frame calibration with a DSLR or other non-cooled camera. Achieving a consistent temperature is obviously a challenge. How important is this, and what are the best practices for creating temperature-matched dark frames?
Thank you so much for saying that! I use a dark library for my mirrorless camera and I try to take dark frames for each 5-degree increment. There is no perfect solution because the temperature is not controlled, but if it’s close enough it will provide a benefit over just nothing.
Wonderful summary! 😊
thank you, I appreciate you saying that!
Greetings from India ! Many congratulations! 🎉.Your gear selection is simply amazing just like your knowledge on the subject and ability to explain the technicalities in simpler terms.
Thank you so much :) That's very kind
Some older ccd's require longer duration flats, or they record a shadow of the shutter. (KAF8300 sensors are a good example) What's really bad is when the "dust" moves over time during a session (mostly a DSLR problem). Flats just make it worse.
I tried a round of low ISO flats, had to shoot a set of bias frames to calibrate the flats in PixInsight. I wasn't exploring it for long term use, just trying to clean up some borderline data. It did work but it's more cumbersome than it's worth. Better data is the solution (and sometimes a better camera).
oh no! Dust that moves around really sounds like the most horrible problem that you can't calibrate out. At that point you just hope it moves around enough to get rejected (kidding)
Excellent video, your the first who actually said when you don’t use darks you still need to calibrate lights with the bias instead.
One other fyi, you said calibration is really important for astrometry when measuring star brightness changes, I think you meant photometry, Astrometry measured position, photometry measures intensity,
great presentation
hey Frank, thank you very much! and yes of course I meant photometry - I need to understand how to fix this in the video :D
Very well explained. Nice job!
@@giuseppiallegro thank you! 😊
great video - thank you
Glad it was helpful!
Very nice and detailed vidéo of calibration frames! I learned alot! Clear skyes from Québec, Canada!
Thanks for saying that I am happy it’s useful! And thanks for wishing clear skies, I could really use some 😭
@@the_space_koala I understand, astrophotography is controlled by something we can’t change, meteo!
Could you put together a simple chart with the different types of frames on the left horizontal axis: darks, flats, bias, dark flats. And across the type such attributes as temperature and ISO (and perhaps others) and a check in the corresponding box if that attribute affects that type of frame. The goal here is to understand what is a "library" of calibration frames. To rephrase, does a library need to have a master bias frame for each ISO and temperature? Currently I'm sticking with ISO of 1600 but my camera is not cooled.
This really is a nice video because it tells us *why* we are taking each type of frame.
Is this correct? Darks already contain bias so if you use dark frames you do not need to subtract bias from the lights. Bias or dark flats are need for flats.
That’s right! You wouldn’t need both! Workflows that use both are aimed at optimizing dark frames i.e. scaling them in case they were not taken correctly
All I understood from that is I'm hungry for some black beans and rice. :)
Don’t forget to measure your ingredients multiple times!
Thank you very much. I can take dark flats using NINA, but I don’t know how to identify them to pixinsight when I use WBPP.
You don’t need to. Dark flats are just darks and WBPP will automatically match the dark with the corresponding exposure length 😊
@@the_space_koala thanks!
May be this smart Space Koala might convince me to take calibration frames 😊Up to now I have only taken calibration frames for my ASI294MC Pro. To get rid of the the amp glow this camera unfortunately suffer from. For other cameras, including mirrorless, I feel the quality usually are OK. The "lights" are more affected by atmospheric conditions to be "perfect" anyhow in my sessions up to now.
If you use your mirrorless with a lens you can also just take a series of calibration frames and reuse them! I for one don’t remove the lens of my mirrorless often so I can even reuse flats between sessions sometimes! And you can create a dark library for each like 5 degree increment in temperature and reuse those as well!
@@the_space_koala Thanks a lot for your tip! I will follow your advice. I love "diversity" so I have a few cameras and lenses to work thru 😊