Rob, most people are afraid of math. They go 'Oh Gawd, I've got to do arithmetic for this? I just want pictures of the stars.' They don't consider that they do arithmetic all day long, from counting change to very fierce mental calculations on everything from driving to playing tennis. But, if you tell someone they have to do something, they all freak out. Figuring out the ADU from camera bit depth isn't that hard, as Stace has shown. In fact, I didn't know it was that easy. But, then again, I never looked at it, either. I always kind of shot for 50% of the histogram to get what I wanted, but this is a more scientific way, and the results should be better. Stace really put this out as a very easy proposition, and more people SHOULD be watching it, and learning from it, if they want better astrophotos.
Thanks Stacy, I have usually done about 10-15 flats ☹️. I will have to pull my socks up and do more. I use a light box for the light source as you say it’s usually cloudy - much like tonight.
Thanks for that Stace, I now know what I have been doing wrong or at least I think so. Going to give it a test now see how it goes, thanks again, Mick.
Hey Brummy Girl AstroStace. This is superb! It makes a change to see the science (Maths) that is involved in creating a image. Keep knocking out the guides/tutorials babs.
Maths is everything! it's the universtial language in engineering which equates to everything being designed, made and built. I can see here when dealing with large numbers 'powers of ten' mathematical equations is used ☺
Great video and thank you. I tried the t shirt method once! Then I purchased a light pad (also labelled drawing, tracing, light box on ebay). Then wrapped a plain sheet of paper over it, taped at the back. Then connected, with a usb cable, a small power bank. Very easy, very quick. I have used it at the telescope and with a dslr after using the dslr with camera lens - no problem. Must start taking more flats!
This is an excellent video and hopefully more people will watch it. You did a good job of explaining everything. I think this sort of video contains exactly what every astro-photographer needs to know to produce good flats that will actually work. When I first started I didn't know that sharpcap was so useful and my flats made things worse until I understood the principles that Stacey put forth here and in her Sharpcap sensor analysis video. Great work Stacey! I wish I had the guts to get in front of a camera but I don't lol
Great vid. I moved from DSLR to OSC last week and its been a headache with flats, now I am sorted! thanks for these vids, reallly good stuff and keep it up.
Hey Stace.. thanks for this vid.. I have watched it many times, along with Ruz's and also Phil from AstroDad videos too, both have the same cameras as I do but gave different ADU Flat figures.. it was doing my head in, but now I understand that it depends also on the Software. It was very daunting as a newbie with an OCS to figure it out. So thanks again for another great video, albeit a few months old :) Stay safe.. cheers John
Thanks for your presentation Stace, this explains a lot! SGPro is what I have been using. The histogram/statistics always show 65K+ regardless of the camera used, so everything is scaled like you said. The Flats Calibration Wizard always starts with the default value of 30K, so now I know where that number comes from. This "full bit" value always appears the same even if different gain is used. Usually the captured lights ADU seems best in the 700-1500 range or the highs get too blown out or over-saturated. Some commentary I have seen suggests flats should be taken in the range where the sensor is still linear, or same number of electrons per ADU. Some sensors have linear response, others do not. Some folks keeps their flats range a little lower perhaps to avoid the higher end non-linear curve. Any comments on the linearity thing? Sorry if I'm drifting away from the intended basics you have shared.
Hey John! That’s great ! You’ve just confirmed a lot of what I was trying to say :) yeah doing flats where the sensor is linear is a better idea, but most sensors these days are linear now. Sharpcap now does a linearity check on sensors and the one I was using in the video is linear up to 99.6% so for that one I could aim wherever I like. I tend to shoot my flats at unity gain regardless and then just vary the exposure time and iPad brightness to get it exactly to what I want
Do your calculations work for CMOS cameras as well. I had no issues with my CCD flats but am struggling with CMOS flats. And no I don't use a T Shirt. I have a 16bit Colour CMOS using APT and I've tried any number of target ADUs but apart from not removing the dust bunnies I'm better off without flats for the dreadful gradients they introduce. I started at 30000 and have gone both up and down and am now looking at advice to try 20000. In APT my tool of choice for getting the setting correct all i see in live view is a variety of green and turquoise screens. ???
Hi Stacy, Another great upload and i love the mathematical computations for flats. I am a DSLR user, and i use BYEOS, and when i take my flats (the same as you BTW i just use a white screen but on my laptop). I keep the same ISO and focus settings, and modify my shutter speed until i have a "central" histogram. Always works spot on, removing any unwanted artefacts. Wouldn't the same be true for CMOS dedicated astronomy cameras ? regardless of bit depth, if we transpose ISO for Gain, in a CMOS camera and just modify the exposure times until we have the same central histogram, would this not work ? I only ask this because i will be purchasing my first dedicated astro cam this year. John
Hi John! You are absolutely correct you can do it this way or as I tend to use APT I like to aim for the correct ADU for each sensor :) it’s just another way of doing it really...I thought people may like to know some of the math behind it all 😀
Good video. I usually do 100 flats and 100 bias. It works extremely well. Funny you made the comment about the white t shirt as I got banding with that and I noticed the material of shirt made a difference I am actually use a pink or salmon colored polyester shirt. Works great and no wrinkles.
Every forum and everyone I know use 18k to 30k ADU for a ZWO 1600mm Pro which is a 12 bit ADC. Do you recommend around 2,000 according to your video as I will try it next time. I noticed after fitting a f0.79 focal reducer it's impossible to get 30k ADU any more. It needs something in the low thousands to stop exposure time of the flats being nearly 2 minutes.
@Crypto Alchemist - I know that with my ASI 1600mm, if I use 20k ADU i get an inverted correction from my flat. There's something fishy about that camera. I do not get that problem when I use 8K to 10K ADU for my flats, however. (Using SGP, btw)
The question is, really, what are you looking at? What numbers? Are you looking at the True ADU value, or are you looking at a 'stretched and scaled' number? For a True ADU value, it's not going to go over 4096, so a 2000 value would be great. But, if it's stretched to a 16 bit number, 30,000 is what you want. I do find it interesting that with a .8 focal reducer you can't get as high an ADU as before, that doesn't make sense, since you should actually be seeing a lower f/ratio. So, what program are you using to look at your historgram, and what scale are you using?
g`day stace i have never tried flats looks very complicated and stressful trying to get it right ... great video... you are always one of the first videos for me to watch when i get notifications on you tube cheers james D
@@AstroStace thanks stace ill get a artist illuminated drawing light pad and have a few goes at it .. ill probably need all the help i can get lol thanks so much for the offer of help cheers
Stace, great video. I was having a problem with flats today and found this to be enlightening. One minor thing about ADU range: I think the range of values given the bit depth of an ADC is [0,2^(bit_depth)-1]? So for instance the range for a 16-bit ADC is 0 to 65535, not 65536. The 16-bit ADC can have 65536 possible values from 0 to 65535.
That’s correct! I recognised my error as soon as the video went out :) you’re the first one to point it out! But either way hopefully you found it useful and it helps :)
Great video, I just got my Hypercam 180c its a massive learning curve from DSLR but thanks to your videos I can run the analysis and do the maths for flats. Im so new to this I love your videos. I have the iPad Pro and a Williams 73 apo, how do you get the iPad secured LOL?
I have good results using AstroFlat and GradientXTerminator in photoshop.... Not sure how does it compare to flat frames calibration. I didn't do the comparison.
Thank you for this video. I get your math on multiplying the bit depth by the desired illumination % but what if your app IS scaling? For example I have a 12 bit one shot color so by the math I would need to aim for ADU 2000. But if I notice APT is scaling to 16 bit? How do I adjust the numbers?
I’ll have to try flats without the T-shirt sometime. Mine are usually OK, but you mentioned that you stretch the T-shirt, which I normally don’t do. I wonder if uneven stretching of the T-shirts is what was causing your gradients? Great video, Stace!
Yeah give it a try! To be honest I tried t shirts all different ways, it was messing up my flats haha. So much better for my setup with out. But that’s not necessarily saying it’ll be best for your setup :) just give it a go
Thank you Stacey, that was a great video. I thought the use of the white board was brilliant. It helped me remember what was going on there. I’m curious how you arrived at 30-50 flats. Just experience or more math? Also, how many darks do you use? Or is that another video? I find that when you take long subs, taking a lot of darks is very tedious. Clear skies, Mark
APT lets you know what the adu is I presume but it does not do it with a dslr, but tankk you for the video because there is always new people joining our hobby that need this explanation. Well done Stace...
You’re absolutely correct Peter! Also thank you for the good feedback. I’ve just updated to say it’s for dedicated Astro cameras only, but I’ll do one for dslr soon :)
Stacy, just seen you on Dylan's Channel giving you a plug. You need to Drink coffee, more caffeine in it to keep you awake lol. I love his channel (and yours of course) his Aussie humour has me in Stitches at times :) John
SGP converts up to 16bit. I was told to go by your cameras Well Depth. On my Qhy 163M is 18 to 20k. So I shot my flats at 9k to 10k. 50% of my cameras well depth.
If it ain’t broke don’t fix it :) you can calculate the required ADU from the well depth yes . My 183c had a well depth of about 16k, once i calculated it all back using the well depth...50%illuminated still ended up being about 2000adu :) but that’s just the way I do it. If there’s nothing wrong with your flats I wouldn’t change them. Thank you for watching though!
Aaah, good to see the H&S Inspector back to interfere. 😁 Interesting, unusual video. This video is better than when people get click happy on their computer. Leaving the beginner to chase the cursor to the next process. Don't know about 12bit to 16bit. Ide be grateful for 1bit of clear sky. 😁 Your doing a great job. Hope you keep it up. Clear sky's.
No, but that’s because I tend to leave my camera on the scope in the same orientation. If I was to move the camera or take it off then yes I would shoot new flats :)
Great info, Stace! Thanks! Other than exposure time when shooting your 50 flats, do you keep all your other camera and OTA settings the same as for your lights and darks?
Thank you! Yes I tend to. So gain , black level/offset etc. The temp I’m not too obsessive about but if the camera is already at -10 and then I shoot my flats then I keep the cooler on
Elaborating pictures and clicking here and there to make a good photo it is useless without knowing what you are doing. That's why your videos are great since if you are going to do something you MUST know what you do, and you explain the background. Otherwise everybody can be a doctor, or an engineer...Great job. So keep on going!
Thanks Stace, these vids are great and help tie it all together. What app do you use for your iPad flats, and do you do it in a dark room or just normal led or incandescent lighting... or doesn’t it matter? Also many say to use dark flats, do you use those? Cheers John.
@@ppi57 i got the rgb app for $ us looks great and you can adjust color brightness have not used yet but thinking about reducing green so i have pinkish screen
Why isn't this video getting love? The Math(s) is/are my absolute favorite part :) Thank you so much, Stace!
Thanks so much Rob! I’m a bit nervous to share it anywhere to be honest! But I’m glad you’ve found it useful!
I do not know Rob? This is one hell of a superb guide.
Simon Fletcher - Astronomy for Beginners -A4B- thanks so much Si!
Rob, most people are afraid of math. They go 'Oh Gawd, I've got to do arithmetic for this? I just want pictures of the stars.'
They don't consider that they do arithmetic all day long, from counting change to very fierce mental calculations on everything from driving to playing tennis.
But, if you tell someone they have to do something, they all freak out.
Figuring out the ADU from camera bit depth isn't that hard, as Stace has shown. In fact, I didn't know it was that easy. But, then again, I never looked at it, either. I always kind of shot for 50% of the histogram to get what I wanted, but this is a more scientific way, and the results should be better.
Stace really put this out as a very easy proposition, and more people SHOULD be watching it, and learning from it, if they want better astrophotos.
@@AstroStace There is no reason to be nervous. You did a great job, and it was clear and relatively easy to understand.
Thanks Stacy, I have usually done about 10-15 flats ☹️. I will have to pull my socks up and do more. I use a light box for the light source as you say it’s usually cloudy - much like tonight.
Hey Steve, don't worry too much if its working for you. might be worth doing a few more though :) 30 + (50 even better)
Thanks for that Stace, I now know what I have been doing wrong or at least I think so. Going to give it a test now see how it goes, thanks again, Mick.
Hope it works for you Mick!
Hey Brummy Girl AstroStace. This is superb! It makes a change to see the science (Maths) that is involved in creating a image. Keep knocking out the guides/tutorials babs.
Maths is everything! it's the universtial language in engineering which equates to everything being designed, made and built. I can see here when dealing with large numbers 'powers of ten' mathematical equations is used ☺
Excellent video. This just got me out of a late night imaging session bind. Thank you.
Great video and thank you. I tried the t shirt method once! Then I purchased a light pad (also labelled drawing, tracing, light box on ebay). Then wrapped a plain sheet of paper over it, taped at the back. Then connected, with a usb cable, a small power bank. Very easy, very quick. I have used it at the telescope and with a dslr after using the dslr with camera lens - no problem. Must start taking more flats!
I found your video to be informative as well as entertaining! Thanks!
Awesome explanation. I love the whiteboard and marker method of teaching. Great job! Now I've got to put it to practice.
This is an excellent video and hopefully more people will watch it. You did a good job of explaining everything. I think this sort of video contains exactly what every astro-photographer needs to know to produce good flats that will actually work. When I first started I didn't know that sharpcap was so useful and my flats made things worse until I understood the principles that Stacey put forth here and in her Sharpcap sensor analysis video. Great work Stacey! I wish I had the guts to get in front of a camera but I don't lol
Thank you very much Ted! Really appreciate the kind feedback :)
@@AstroStace Most welcome Stacey! Looking forward to more interesting Astro vids!!
Thanks for this! Much appreciated and well done!
Yessss this is the kind of detail I love! Great video as always!
Thank you 😊
Great vid. I moved from DSLR to OSC last week and its been a headache with flats, now I am sorted! thanks for these vids, reallly good stuff and keep it up.
Good explanation. Thank you
This was excellent information. Thanks.
Very helpful, i've definitely had over exposed flats until I watched this!! Thanks!
What a fantastic video! This is a great demystification video on flats. Thank you so very much!!!
Hey Stace.. thanks for this vid.. I have watched it many times, along with Ruz's and also Phil from AstroDad videos too, both have the same cameras as I do but gave different ADU Flat figures.. it was doing my head in, but now I understand that it depends also on the Software. It was very daunting as a newbie with an OCS to figure it out. So thanks again for another great video, albeit a few months old :) Stay safe.. cheers John
Good video Stace, flats are the most complicated calibration frames but therefore the most interesting ones
Thanks for your presentation Stace, this explains a lot!
SGPro is what I have been using. The histogram/statistics always show 65K+ regardless of the camera used, so everything is scaled like you said. The Flats Calibration Wizard always starts with the default value of 30K, so now I know where that number comes from. This "full bit" value always appears the same even if different gain is used. Usually the captured lights ADU seems best in the 700-1500 range or the highs get too blown out or over-saturated.
Some commentary I have seen suggests flats should be taken in the range where the sensor is still linear, or same number of electrons per ADU. Some sensors have linear response, others do not. Some folks keeps their flats range a little lower perhaps to avoid the higher end non-linear curve. Any comments on the linearity thing? Sorry if I'm drifting away from the intended basics you have shared.
Hey John! That’s great ! You’ve just confirmed a lot of what I was trying to say :) yeah doing flats where the sensor is linear is a better idea, but most sensors these days are linear now. Sharpcap now does a linearity check on sensors and the one I was using in the video is linear up to 99.6% so for that one I could aim wherever I like. I tend to shoot my flats at unity gain regardless and then just vary the exposure time and iPad brightness to get it exactly to what I want
Excellent, thank you for taking the time!
Do your calculations work for CMOS cameras as well. I had no issues with my CCD flats but am struggling with CMOS flats. And no I don't use a T Shirt. I have a 16bit Colour CMOS using APT and I've tried any number of target ADUs but apart from not removing the dust bunnies I'm better off without flats for the dreadful gradients they introduce. I started at 30000 and have gone both up and down and am now looking at advice to try 20000. In APT my tool of choice for getting the setting correct all i see in live view is a variety of green and turquoise screens. ???
I shall have another go at doing my flats thanks
Wow! Fantastic information Stace! Kind of busy these days, didn't see this early enough! Great Video!
I just met you with this video. Great job! Very clear and precise! I made flats using my computer screen too. Greetings from Argentina! :)
Ah hello!!! Glad you liked the video! 😊
Great videos i have watched flats one 3 times. i could not make my mini tablet work until i got R G B light app would you reduce green light
G’day Stace
Thank you very much !
I finally understand the values I should be aiming for
Cheers
excellent explanation.... great post
Hi Stacy,
Another great upload and i love the mathematical computations for flats. I am a DSLR user, and i use BYEOS, and when i take my flats (the same as you BTW i just use a white screen but on my laptop). I keep the same ISO and focus settings, and modify my shutter speed until i have a "central" histogram. Always works spot on, removing any unwanted artefacts. Wouldn't the same be true for CMOS dedicated astronomy cameras ? regardless of bit depth, if we transpose ISO for Gain, in a CMOS camera and just modify the exposure times until we have the same central histogram, would this not work ? I only ask this because i will be purchasing my first dedicated astro cam this year.
John
Hi John! You are absolutely correct you can do it this way or as I tend to use APT I like to aim for the correct ADU for each sensor :) it’s just another way of doing it really...I thought people may like to know some of the math behind it all 😀
Great stuff, appreciate the information ,thank you.
Good video. I usually do 100 flats and 100 bias. It works extremely well. Funny you made the comment about the white t shirt as I got banding with that and I noticed the material of shirt made a difference I am actually use a pink or salmon colored polyester shirt. Works great and no wrinkles.
Every forum and everyone I know use 18k to 30k ADU for a ZWO 1600mm Pro which is a 12 bit ADC. Do you recommend around 2,000 according to your video as I will try it next time. I noticed after fitting a f0.79 focal reducer it's impossible to get 30k ADU any more. It needs something in the low thousands to stop exposure time of the flats being nearly 2 minutes.
No, not necessarily. It sounds like it’s been scaled to 16bit as I mention in the video. So 18k to 30k is fine
So when it’s scaled to 16 bit you get the range 0-65k ish. So 30k is just under 50% illuminated
@Crypto Alchemist - I know that with my ASI 1600mm, if I use 20k ADU i get an inverted correction from my flat. There's something fishy about that camera.
I do not get that problem when I use 8K to 10K ADU for my flats, however. (Using SGP, btw)
The question is, really, what are you looking at? What numbers? Are you looking at the True ADU value, or are you looking at a 'stretched and scaled' number? For a True ADU value, it's not going to go over 4096, so a 2000 value would be great. But, if it's stretched to a 16 bit number, 30,000 is what you want.
I do find it interesting that with a .8 focal reducer you can't get as high an ADU as before, that doesn't make sense, since you should actually be seeing a lower f/ratio.
So, what program are you using to look at your historgram, and what scale are you using?
g`day stace i have never tried flats looks very complicated and stressful trying to get it right ... great video... you are always one of the first videos for me to watch when i get notifications on you tube
cheers
james D
Thanks so much James! Always happy to help, let me know if you need any with the flats! Clear skies!
@@AstroStace thanks stace ill get a artist illuminated drawing light pad and have a few goes at it .. ill probably need all the help i can get lol thanks so much for the offer of help cheers
Stace, great video. I was having a problem with flats today and found this to be enlightening. One minor thing about ADU range: I think the range of values given the bit depth of an ADC is [0,2^(bit_depth)-1]? So for instance the range for a 16-bit ADC is 0 to 65535, not 65536. The 16-bit ADC can have 65536 possible values from 0 to 65535.
That’s correct! I recognised my error as soon as the video went out :) you’re the first one to point it out! But either way hopefully you found it useful and it helps :)
Love this version of PowerPoint, much more sympathetic
Nice to see 'powers of ten' mathematical equations being used 👌🔭
Never thought of using the mrs iPad, good shout!
Just make sure to take the eye care setting off :)
Great video, I just got my Hypercam 180c its a massive learning curve from DSLR but thanks to your videos I can run the analysis and do the maths for flats. Im so new to this I love your videos. I have the iPad Pro and a Williams 73 apo, how do you get the iPad secured LOL?
I point my telescope towards a wall inside with the light on and take them while rotating it so the average out.
I have good results using AstroFlat and GradientXTerminator in photoshop.... Not sure how does it compare to flat frames calibration. I didn't do the comparison.
Thank you for this video. I get your math on multiplying the bit depth by the desired illumination % but what if your app IS scaling? For example I have a 12 bit one shot color so by the math I would need to aim for ADU 2000. But if I notice APT is scaling to 16 bit? How do I adjust the numbers?
That’s also in the video! :)
Basically if your app scales, treat it as a 16 bit camera
I’ll have to try flats without the T-shirt sometime. Mine are usually OK, but you mentioned that you stretch the T-shirt, which I normally don’t do. I wonder if uneven stretching of the T-shirts is what was causing your gradients? Great video, Stace!
Yeah give it a try! To be honest I tried t shirts all different ways, it was messing up my flats haha. So much better for my setup with out. But that’s not necessarily saying it’ll be best for your setup :) just give it a go
Good information thanks for putting this together! On your ASI294MC how long are you shooting each flat when you are at your target ADU?
Nice one Stace
Thanks Ryan!
Thank you Stacey, that was a great video. I thought the use of the white board was brilliant. It helped me remember what was going on there. I’m curious how you arrived at 30-50 flats. Just experience or more math? Also, how many darks do you use? Or is that another video? I find that when you take long subs, taking a lot of darks is very tedious. Clear skies, Mark
You actually started by writing "So"........made me chuckle.
Brain was definitely struggling with multitasking there 😂
APT lets you know what the adu is I presume but it does not do it with a dslr, but tankk you for the video because there is always new people joining our hobby that need this explanation. Well done Stace...
You’re absolutely correct Peter! Also thank you for the good feedback. I’ve just updated to say it’s for dedicated Astro cameras only, but I’ll do one for dslr soon :)
Stacy, just seen you on Dylan's Channel giving you a plug. You need to Drink coffee, more caffeine
in it to keep you awake lol. I love his channel (and yours of course) his Aussie humour has me in Stitches at times :)
John
Thanks John! Yeah I get up to like 5 cups a day at work sometimes so then switch over to tea at night haha! Got a serious caffeine problem! 😂
SGP converts up to 16bit. I was told to go by your cameras Well Depth. On my Qhy 163M is 18 to 20k. So I shot my flats at 9k to 10k. 50% of my cameras well depth.
If it ain’t broke don’t fix it :) you can calculate the required ADU from the well depth yes . My 183c had a well depth of about 16k, once i calculated it all back using the well depth...50%illuminated still ended up being about 2000adu :) but that’s just the way I do it. If there’s nothing wrong with your flats I wouldn’t change them. Thank you for watching though!
Or 30k adu when I stretch it up to 16 bit :)
Aaah, good to see the H&S Inspector back to interfere. 😁 Interesting, unusual video. This video is better than when people get click happy on their computer. Leaving the beginner to chase the cursor to the next process.
Don't know about 12bit to 16bit. Ide be grateful for 1bit of clear sky. 😁
Your doing a great job. Hope you keep it up.
Clear sky's.
Thanks Melvin for the good feedback! Haha yes Luna was here to make sure I was explaining everything as best I could 😀 clear skies!
Hi Stacey do you take flats every time you do some imaging
No, but that’s because I tend to leave my camera on the scope in the same orientation. If I was to move the camera or take it off then yes I would shoot new flats :)
Great info, Stace! Thanks! Other than exposure time when shooting your 50 flats, do you keep all your other camera and OTA settings the same as for your lights and darks?
Thank you! Yes I tend to. So gain , black level/offset etc. The temp I’m not too obsessive about but if the camera is already at -10 and then I shoot my flats then I keep the cooler on
Elaborating pictures and clicking here and there to make a good photo it is useless without knowing what you are doing. That's why your videos are great since if you are going to do something you MUST know what you do, and you explain the background. Otherwise everybody can be a doctor, or an engineer...Great job. So keep on going!
Thank you so much 😊
good vid Thx
ADU?
Ayn advice or guidance for DLSR users?
There will be :) but for now, pop it into AV mode and aim for the histogram to be around the middle :) or just to the left of middle
Thanks Stace, these vids are great and help tie it all together. What app do you use for your iPad flats, and do you do it in a dark room or just normal led or incandescent lighting... or doesn’t it matter? Also many say to use dark flats, do you use those? Cheers John.
Thanks for sharing. I got the chance to view a rocket launch in 2018. Amazing experience. I posted a pretty cool video of the trip to my page.
Stace I felt like is was in school just watching this :)
how do you set your iPad to plain white screen?
I use the notepad app, and set up guided access :)
Thx Stace, I did a number google search's, but nothing came up.
@@ppi57 i got the rgb app for $ us looks great and you can adjust color brightness have not used yet but thinking about reducing green so i have pinkish screen
Thx folks, I ended up splurging on the "Flatmaster" hardware.
What’s an ADU? You didn’t define the term.
👍