Astrophotography Calibration Frames Simply Explained

[@moneyoffsoftware]

At last a straight forward explanation of darks and flats, some of the videos out there are so confusing. Thank you

[@AstroEscape]

Thank you Moody, I'm glad it could help!

[@ingemargunnarsson9146]

Very good video. I am expereinced photographer, but new into astro so those kind of videos help me a lot - THANKS!!

[@AstroEscape]

Thank you! If you have tips about other forms of photography, I'd be new to some of them too!

[@Rainy78]

Thanks for sharing! New subscriber here starting on my astro journey. I've tried a bit with my DSLR, but recently have bought a mount and Skywatcher Quattro 130pds Newtonian to start with. A few more thousand $ to spend yet on other gadgets before 1st light, but man am I excited!

[@AstroEscape]

Well, it's been over a week... did you get a night under the stars yet?

[@colebutler6535]

this is the best explanation for this subject i’ve been so confused on trying to figure this out

[@AstroEscape]

Thanks Cole, glad it help you!

[@Mainuh]

Thanks Daylon. That's the clearest, most concise explanation i've seen for this topic. I've never done them before but about to start with my new dedicated ASI 533MC Pro and ZWO FF65 setup. Have you done a video on storing all the photo data over time? I can see just shooting lights for the past 7 nights here in AZ that it's going to get complicated to catalogue it all for use later.

[@AstroEscape]

I have not done a video yet about storing the data. That is in the backlog and should be coming in a month or two. I have to buy something first!

[@climus]

This is so helpful. I can't wait to make my images better

[@AstroEscape]

Thanks Climus, glad it could help!

[@PatJones82]

Very helpful! Much appreciated! :)

[@AstroEscape]

Thanks for watching! Did it help clear up any questions?

[@davegibson6604]

Great info. I might add that for lights, lots of frames. More subs mean an increase in signal to noise ratio. Also, a problem I have with my ASI294 is that very high speed bias frames have inconsistent results. This camera (like the 183 and 1600) do better with dark flats....1/10 shutterspeed for the 1600 and 2-3 seconds for the 183 and 284.

[@AstroEscape]

Lots of frames is why I put in "the sky is the limit." Yeah, bad joke territory, but the more, the better! For the 294, I don't do bias. But, DSLR's can benefit from them depending on the sensor. Most dedicated astro cams can just do dark flats :)

[@jafe860]

I learned so much from watching this. Thank you! I have a zwo 585mc. What exposure and gain settings should I set when taking flat frames?

[@AstroEscape]

Leave the gain where it was when you were taking your light frames. For flats, you want it to be between 3-10 seconds based on your light source. If you aren't using something like an ASIAIR that can calculate it for you, aim for the peak of the histogram to be in the middle.

[@anzaeria]

Out of curiosity, does the focus setting have to be the same when shooting Flats? Also, I'm not sure if the temperature has to be consistent as well. If the temperature is not an issue, could I photograph a blue sky during the day with the same lens and use that as a Flat? Obviously, the shutter speed would normally be high so I could use an ND filter to increase the exposure time.

[@Zuneku13]

This is really useful information >.

[@AstroEscape]

I'm glad that it was helpful!

[@arthurkaye8999]

Loved your video very simple and easy to follow. One question I have is, how long should my exposures be when taking Flats with a dedicated astronomy camera?

[@AstroEscape]

Aim for no less than 3 seconds, no more than 10. That should make sure both the dust and vignetting are properly exposed and calibrated out in processing :)

[@arthurkaye8999]

@@AstroEscape thanks for that. Its currently winter where i am and hardly any clear nights. Gathering alot of theory am impatient to put into practice.

[@ashishkshahane]

Nicely explained. Thank you so much!

[@AstroEscape]

Thank you for your kind comment! Clear skies :)

[@Mrflightlogic]

Great video! You went a bit fast when you described dark flats. How are they different? I have captured flats by following your guide. And I have captured darks... Am I done? In other words, what is a dark flat? Or is this just terminology that is unclear? Thanks!

[@AstroEscape]

Dark flats are dark frames captured at the same exposure time as your flats. For example, if your flats came out to 4.3 seconds, the dark flats would also need to be 4.3 seconds for calibration software to run it all properly. I hope that helped, however I am working on a 2.0 version of this that's a little bit more in depth :)

[@blanejnasveschuk6351]

And, if the flat frame exposure is 4.3s at a particular temperature, then the corresponding “flat dark” frame should be at the same temperature that the flat was taken. Correct? The flat dark calibration is geared at removal of the small amount of sensor noise, hot pixels, and amp glow, etc. from “flat” resulting in a calibrated master flat. Am I thinking right? I am glad you emphasized placing the telescope cap “on”, for this flat dark frame calibration frame! Obvious, but important detail, not to be overlooked! BTW ASIAir Pro or Plus has a wonderful auto calculation function to optimize proper ADU for flat exposure, given a consistent T-shirt/sky or light panel illumination. Then a second feature allows the flat exposure time to be efficiently imported for the “flat dark”. Still have to remember to cap the scope or swing in an “opaque” on your filter wheel when taking the flat dark. Please let me know if my thinking is off track. TY for your video.

[@mikelockwood2104]

Good stuff....I'm glad I found your channel. Thank you

[@AstroEscape]

Thanks for watching! Was there anything I wasn't clear about?

[@mikelockwood2104]

@@AstroEscape I think you covered it well.....I do have a question though ( as a newbie into astrophotography ). I have the 7 position ZWO EFW filter wheel and plan to use the Astronomik 1.25" Dark Frame Filter in one of the slots to do dark frames during the imaging session. Do you know if any manufacturer makes a Flat Frame filter ? I'm trying to automate the entire process - lights, darks & flats using the ASI Air Pro. Thank you for your reply and interest in helping others learn this awesome hobby.

[@AstroEscape]

@@mikelockwood2104 I do not know of any manufacturer that does. Flats are probably the only thing you can't automate. If you added anything to the filter wheel to do that, you'd be missing the dust that's on the telescope and only get what's on the sensor/filter. Luckily, flats and dark flats are fast, so it's a small time investment!

[@mikelockwood2104]

@@AstroEscape that does make sense about the dust on the objective. Thank you for your prompt reply

[@jtepsr]

can you explain how you do dark flats, do you remove the white t shirt and light panel, i am confused

[@marekmiszczak3266]

2:56 the second you break the seal (...) you can introduce new dust(...) 3:26 slap an old cotton tshirt that will rain down a gazillion fabric specs right on the front element :D

[@carlosmaurixio]

Front telescope dust is way out of focus and doesn’t typically show up on images. The dust that shows up on images are the specs on the camera’s glass or on the filters directly in front of the camera glass.

[@larkinsen]

Hi.Great explanation.I just got an ASI 533MC PRO...so my question as a noob with dedicated astrocams(I used a DSLR before this).Before I begin a session first thing is I have to wait until the camera cools to -10C (my temp setting) wright? .And that is available for dark frames I'm guessing.Thanks.

[@AstroEscape]

With dedicated cams, you can do the darks at any time. Pick a cloudy day, attach your scope, and throw it in a dark room and run the frames. As long as no light gets in, you are good. but, repeat the process every six months to deal with the aging of the sensor of the camera and temperature changes of the year. I usually do a set of 5, 10, 30, 60, 120, 180, and 300 second darks, all at -10 Celsius. Just keep a master dark using DSS or Pixinsight for reprocessing later on if you want to reprocess after a few years. Keep in mind that the -10c is lower than ambient temperature, which changes with the seasons which is why I mentioned every 6 months beyond the aging of the sensor. As for your first question, turn the camera and the cooling on as it's getting dark and let it cool down. Same principle applies with visual and using a DSLR. Let the scope/eyepieces/DSLR match ambient temperature. But for a dedicated camera, you need to keep the sensor cooler, so let it cool down to the desired temp before you start shooting. Have fun with that 533, it's a great camera!

[@larkinsen]

@@AstroEscape Thanks for this elaborate response.Clear skies.

[@davegibson6604]

The 533 is a great camera. Cooling takes care of temperature related problems and the 533 doesn't suffer from amp glow. Most people I know with this camera don't take darks....just flats.

[@Lumber91]

What filter(s) would you recommend for a beginner with a OSC?

[@AstroEscape]

I use the Optolong L-Pro and L-enhance based on what I'm shooting. Those work well enough, and I live in a Bortle 9 area :)

[@arshadwm]

Thank You

[@AstroEscape]

You're welcome, I hope it helped!

[@KemuSabi-t6b]

Which light panel have you got or recommend for calibration frames?

[@AstroEscape]

Just a cheapo tracing pad from Amazon is what I use. Works out fine.

[@entropytango5348]

Sensible advice covering all bases

[@AstroEscape]

Thank you for the feedback!

[@hedgebetss]

Can you use a generic stock of darks and flats that are not to the same settings as the lights. Will it affect the end results.

[@AstroEscape]

For darks, yes, as long as your camera is cooled. For flats, no. Those are better taken during the session because of dust that may settle on the objective of your telescope/camera lens (on the glass) and could get moved when you move the setup, changing the results.

[@stefanosks6127]

what exposure settings we have to use on flats and dark flats frames? 😀

[@AstroEscape]

Flats are best done in auto mode, as long as the exposure is between 3-10 seconds long to properly expose the dust and vignetting. Whatever your control program calculated the exposure for, that's how long the dark flats need to be.

[@stefanosks6127]

@@AstroEscape thanks ✌️✌️

[@fretBeastForever]

I wish you`ll put a video to show us the process in real life :)

[@AstroEscape]

I certainly can make one!

[@RaisinEnjoyer]

2:50 that sound made me shit my pants, it sounded like it was coming from outside my house

[@AstroEscape]

Whoops! Sorry about that. I get it, we have a phone for after hours calls for work.... any time I hear another phone with that ringtone I'm immediately like "crap.... gotta work!"

[@jeffreyvictor3678]

Good Info!

[@AstroEscape]

Thank you! Apologies for the late response, if you check my community tab, been dealing with healing! Do you have any questions I may not have covered in the video?

[@jeffreyvictor3678]

@@AstroEscape yes Sir I do…after obtaining a PA, do you manually move the mount back to “home” position or do you slew to Vega (or other bright star) from the 60’ RA position the mount is in after PA?

[@AstroEscape]

@@jeffreyvictor3678 I usually slew to my focus star after PA, then send to home and do another PA to be sure. The best thing you can do is do that just before astronomical twilight is over, that way you can maximize time on the target of the night!

[@jeffreyvictor3678]

@@AstroEscape ty Daylon…it is exactly what I will try next clear night here in GA. We have been under spring rains/clouds everyday except 1. Also, I watched your video on the setup and work flow 3 times and took notes. Thinking I’m going to produce the “work flow” into a flow chart type sequence or something similar!

[@tommypaul9036]

In using a DSLR and 135 mm lens, are the calibration frames shot in RAW or JPG?

[@AstroEscape]

Always RAW. JPG doesn't contain all of the data that RAW does.

[@05.aishiqmishra4]

i don't know if you still answer but in case of doing smartphone and telescope astrophotography do i have to crop zoom to take the dark flat and bias frames so the vignetting isnt visible? i do need to leave the lights as however it is though

[@AstroEscape]

If you didn't crop for your lights, don't crop for the flats or any dark frame. The calibration frames will need to be the same in pixel size (height & width) to properly calibrate vignetting.

[@05.aishiqmishra4]

Oh.. still my images have a large amount of vignetting. what i mean is its only a circle view i can see else it is all dark I feel like buying a new dslr if that could fix anything I am new into astrophotography

[@hangerbird]

Regarding Flats... should the shutter speed be slower than what you have been taking pictures of? Not clear on what the image, for a Flat, is supposed to look like.

[@AstroEscape]

It should only be a few seconds of exposure. Just long enough the camera sees the dust and the histogram is balanced. They should look like the frames in the section where I mentioned keeping an eye on the shutter speed. Thanks for your comment!

[@TeamGamingSWE]

During my session I had to flip the scope to continue shooting, I tried to frame the target as similar as I could to how it looked before only that it was turned 180 degrees. I took flats after the session. Will they work for the images I took before I flipped the scope and possibly rotated the camera slightly?

[@AstroEscape]

I would watch rotating the camera because dust will end up in a different spot in the field of view in the picture. But if you just simply flip the scope, no issues there since meridian flips are a common thing :)

[@Stefan-Astro-Art]

maybe a stupid question i am new in astrophotography, Do i have to use the same filter as i used in the light frames? And i got the William optics flattener/reducer 6AIII, now like the name sais Flattener, DO i still need to shoot flat frames?

[@AstroEscape]

For flats, use the same filter. Don't even remove it. If there was dust on the filter when you put it in, you'll want to do your flats and dark flats with the filter still there so the dust can be calibrated out.

[@Stefan-Astro-Art]

@@AstroEscape okay thanks for the info. I created a library of dark without filter but with flattener on. Next time I'll make a map dark flat with L pro and L enhance. Good to know.

[@astrovert.ed2321]

❤

[@AstroEscape]

[@nelsonrivera6575]

Subscribed ,total noobie , i really enjoy your beguinner video , i need all the help i can get , like how to use astrophotography software, thank you

[@AstroEscape]

Thank you! Other software videos are in the plans! Anything specific you are looking for?

[@nelsonrivera6575]

@@AstroEscape yes maybe how to work with n.i.n.a and atp , thank you , also connections , these are overwhelming given the fact that everybody does it different for what i’ve seen , thank you so much for thinking of us( noobies)

[@poco-dn6xz]

for bias frames the shutter should be the fast i got it but what should be the iso and aperture same as light frames ?

[@AstroEscape]

Yes, the only thing you change is the shutter speed.

[@MrGeert1972]

If I go to fasted shutter speed, my iso also goes to max of 25600 same for the fats.

[@manccyclist]

What am I doing wrong here ? 23:03:10: Running command: requires 23:03:10: # Convert Bias Frames to .fit files 23:03:10: Running command: cd 23:03:10: 'biases' No such file or directory 23:03:10: Error in line 24: 'cd'. 23:03:10: Exiting batch processing. 23:03:10: Setting CWD (Current Working Directory) to '/Volumes/Samsung_T5/Photos/Astro/Siril/Back garden' 23:03:10: Script execution failed.

[@AstroEscape]

To me, it looks like you are processing directly off of a tablet/phone. The files need to be on a hard drive on your computer for it to work.

[@manccyclist]

@@AstroEscape they're on a 2 TB SSD portable hard drive connecter to my MacBook Pro...

[@AstroEscape]

Try processing on the main drive for the MacBook, then saving the completed files on the portable drive after you're done. I always use the fastest drive available to process with, which is never a portable drive. It's always an internal drive. I hope that helps!

[@manccyclist]

@@AstroEscape I'll let you know the outcome...