Struggling to understand calibration frames for Astrophoto? Watch this!
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- Опубликовано: 4 июн 2020
- Calibration frames can be absolutely mystifying for beginners in astrophotography and astroimaging. And yes, they can be quite confusing! But the truth is, they're quite simple once you understand them - and yes, you can understand them, and learn how to take them, by watching this video (and other videos on my channel!)
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#astrophotography 
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Cheat Sheet on Calibration Frames: drive.google.com/file/d/1I1deTi8sCFIn_bwQbYiqqxliVLInsGx6/view?usp=sharing
Trying to catch up. Ooohhhh! My head hurts... 😉
Cuiv could you possibly do a follow up on taking those NINA dark flats and flats to pixinsight, preparing them and applying them to lights? I think I have the master dark down now but I am not sure of thew process to combine with the flats. Love your work!!
Appreciate all your videos Cuiv. Have learned so much from them. Could you make a video on using an OSC or Mono Astro Camera for the first time? Thanks.
Very well explained as usual. I do take bias frames with both my ccd and my cmos cameras but did not know about the asi1600 liking 0.1 second bias. I may even try without bias for it. I have a flat panel on my wish list. It seems so much easier! Just need to find the cash and convince my wife how important it is - they do seem rather expensive. I currently use an old t-shirt stretched over an embroidery hoop which sirs on top of the scope for sky flats but the exposure time varies every time i take them and even during taking a set plus you can get gradients with dusk/dawn flats so a flat panel would be great, especially with NINA’s flats routine. Thanks for the video.
Yeah, the 0.1s suggestion comes from multiple reports on CloudyNights - I haven't personally tested it. But I assume it is true - I believe the 1600MM is the reason bias frames have been deviled for CMOS sensors. But then, I don't take bias frames, so... And yes, I used the same technique as yours for flats a while back. But an adjustable panel bought me peace of mind and ease of use - and I value laziness above all else :D I hope you can convince your CFO about it - it's a good investment (just avoid the Geoptik ones - they are quite uneven at the edges - so do your homework with reviews first!). Good luck and clear skies!
Great explanation,your so easy to follow on all your videos thanks
Hey, thank you very much for this great video. Very useful. One quick question : you mentioned to have like a playlist for optimal exposure length. Can you share it ? Cheers.
Cuiv, excellent explanation! Have a great weekend.
Thank you! You too, and clear skies!
Another useful, great video. I'm familiar to subs from my DSLR works, and never had problem with flat frames. I noticed that no one mentions about "same focus with lights in flats", including you. About one year ago when I started astrophotography with my DSLR, I've been tought to set focus as same as light frames. As reason it's said, vignetting area (or surface) is changed due to focus. Was it an urban legend?
Thanks for the question Volkan! I've seen it pop up on Facebook as well. It is as you say an urban legend. Flats are not affected by small changes in focus, such as those caused by temperature changes or filters. For example, dust mote sizes on the image depend uniquely on the incoming light ray angles (determined by focal ratio), physical dust mote size, and distance of the dust mote to sensor. Refocusing in some systems such as those where the primary mirror is moved (SCT for instance) does change the focal length and thus the focal ratio slightly, but unless you're turning the knob tens of times, there is no measurable impact! I would avoid changing the focus too much however, as I think that this does affect vignetting - but again that would be for large changes in focus.
Thank you for all the right info in one video... 👍 But after watching the whole 27 minutes I now understand the irony of the title. This one will take a lot of rewinds. :)
Just to play it safe I take my flats at the same gain...I use an artificial light source and use APT and NINA eventually. Using the histogram at the 1/3 from left is difficult to determine with a colour camera as the R, G, B peaks are not in the same area....
Very informative video Cuiv. Might I ask that in your next video you include a flowchart for the various types of frames as a visual reinforcement of the concepts. It all gets very confusing with similar terminology for different frames. On the flat panel, most are PWM controlled for brightness. Is the PWM frequency likely to impact on flat frames since CMOS chips suffer with rolling shutter issues? For example while playing around with flat frames I have noticed banding in the live feed from the camera. What is your preferred light source. EL panel or LED tracing tablets?
The next video is already done and will come up tomorrow, but I will make a chart and link it from the description (later today, I'm going paragliding first :-) ). Thanks for the advice! I use the Artesky Flat Field Generator, which is LED. I intentionally take longer flats to avoid just that issue... Although I haven't tested with short flats! As for the bias frames, since they're taken with the dust cap on, the flat panel should not be relevant :-)
@@CuivTheLazyGeek oops told you it was confusing :)
@@RobB_VK6ES Here is a cheat sheet :) drive.google.com/file/d/1I1deTi8sCFIn_bwQbYiqqxliVLInsGx6/view?usp=sharing
@@CuivTheLazyGeek excellent Cuiv. Just what I needed :)
Wonderful! Thank you
Thank you!!
Nice work Quiv 👍
Thanks 👍
Thanks, I now know less than I already knew before watching this!
Rather new to this hobby. My kit is clearly more modest than yours, which leads me to asking, do you dismantle everything each night and bring it inside? I know there's debate about covering a telescope, but to date I break everything down and bring it inside. Weather permitting, I set up about 100 feet away requiring a wheel barrow and many trips to the house. Just curious.
I keep everything assembled all the time, under a Telegizmos 365 telescope cover!
Hi Cuiv, dumb question probably but when taking FLATs, DARKFLATs and DARKs ( but not necessarily in that order ) does the Telescope have to be in focus .
Not for darks and dark flats. In rough focus for flats is psychologically better.
I thought reed noise was from a bad saxophone player. Read noise on the other hand. LOL Thoroughly enjoying you channel, just had to pick on you.
I sold my mount today got to wait 3 weeks for the new one. just as well theres no true darkness :)
Oooh yes now's not a good time of the year for DSO imaging... Glad you got your new mount! I'm waiting for my Crux 140Tv to come back from repairs....
I would love it if you would change that White Light bulb to a Red One.
I have learned a lot from your Videos, Thank very much for making them.
I always mean to, never get around to it!
I have a question
If you take a very long exposure and you don’t change the ISO ( which I think you shouldn’t ) , won’t the flat image be over exposed - too bright ?
The histogram will be too far to the right - and I thought it should
Be in the middle .
Thank you
Flats are Histogram dependant. The exposure time is calculated so that it remains in the center. For the camera i have (ASI294MC PRO) it usually is between 2-4 seconds so as to not have read noise
So your obviously taking these calibration frames at the same time on the same chip..how do you keep track of them? Is there a way of numbering them, say for a digital camera?
My understanding is that it is common practice to take dark, dark flat, and bias frames once every six months or so. But doesn't this assume that the camera is mounted in exactly the same position over that time? For example, if the camera is rotated 5 or 10 degrees from one session to the next, or perhaps that much over a 6 month period, won't that change the alignment of the dark signal or fixed pattern noise that the dark, dark flat or bias frames are supposed to remove? In other words, I am confused as to how you can "get away" with taking these calibration frames so infrequently.
Dark/bias/flat dark frames don't care about orientation - they're relative to the sensor only, and you can't change the sensor's position with regards to itself! Flat frames is another story - they are relative to the optics, so in that case yes, if there is rotation for instance they need to be retaken!
I have a 183 on the way. Wish I had gone for the 533 now: just to be lazy :)
Did you get the OSC version of the 183? If you're going to use it with a short scope or camera lens the extra resolution can be worth it!
@@CuivTheLazyGeek Yeh, the OSC. 714mm, I think I may just be ok. But 2x2 binning may be in order. Should have watched your vids first
I recently got the 183 OSC Pro version. I’m liking it so far. I use it with a 600mm doublet and the image scale is .83” which is ok but I’m going to try binning it 2x2 and see if it improves it.
Darks & Dark Flats - Can I take without my telescope? In other words, I've got my camera plugged into power & usb right into my computer. Can I let er' rip for doing Darks & Dark Flats?
Yep, it's fine! As long as light is not hitting the sensor, darks, dark flats, and bias frames can be taken - equipment connected to the camera is irrelevant!
ffs, I saw that there was 1 533 camera in stock and i accidentally bought it, hope i made the right decision lol i heard the altiar may be better of the same and it's cheaper. but pink, ew.
The 533MC Pro is an excellent camera - I don't think you'll be disappointed. Since it's the same sensor, I don't know that the Altair version would be better....
" warning " Flat frames are monsters and can cause nightmares.. (DSLR) are the worse...
The flat frames are dark and full of terrors.... :-) I absolutely agree - I have a mad amount of respects for those who persist with DSLRs
i was doing good until darkflats happened
Nope, no reply, on my own…again.