My Patreon: www.patreon.com/cuivlazygeek Here is an EXCELLENT explainer by Dale Ghent, one of the NINA developers: daleghent.com/2020/08/understanding-camera-offset My videos on gain, etc: ua-cam.com/video/GKXkM_FbFgg/v-deo.html and ua-cam.com/video/SYQ1i4k62eI/v-deo.html Amazon affiliate: amzn.to/3hTB5Ne Agena affiliate: bit.ly/3Om0hNG High Point Scientific affiliate: bit.ly/3lReu8R All-Star Telescope affiliate: bit.ly/3SCgVbV Dwarf 2 Smart Telescope: bit.ly/3SyChXu Seestar S50: tinyurl.com/3n62hpzx
Two problems with making a video on 25th December are the fact that for at least 364 days of the year, people will be watching on the wrong day for you to greet them as you did. And of course countless millions of people don't celebrate the day. Nonetheless, thank-you for your thoughts and for the video. 🙂👍
That histogram would be more useful if it could be switched to a logarithmic wavelength display. That would spread the low end for you, if the software has that facility,
What I have learned is that you should always make sure your histogram is as far away from the left side of the histogram as possible to prevent clipping since what we image is so faint. Because this is a linear RAW image that will be stretched later, don't worry about the peak being too far to the right as long as it does not exceed the 1/3 of the histogram as we can fix this with the histogram stretch in post processing. Already messed up and imaged at zero offset? Don't throw those frames away, you can add a pedestal when you integrate. Yes you lost data but you can still process your image. And yes whatever you change whether it be the gain, offset, temperature, and even the USB limit (yes that can cause issues too like banding!) take new calibration frames. Thanks for making this important video Cuiv and Happy Holidays!
I breathed a sigh of relief after checking some old bias files. With a gain of 120 and an offset of 50 on my ASI294MC pro, it appears that I've been doing it right, more or less. Thanks for the clear explaination of what offset is all about.
@@CuivTheLazyGeek I should mention that I don't take biases everytime I shoot. In fact, I just subtract off the bias value when I do my stacking in SIRL--supposedly less noise added to the result.
@@richardshagam8608 having a bias library you keep reusing is fine, I do the same :) But what do you mean by "you just subtract off the bias value when you do your stacking"?
Great video Cuiv. When I started this hobby back in 2021, I searched for answers to the mysterious offset, it seemed no one wanted to talk about it or if they did it was "yeah just set it at 50". I finally figured it out on my own, after much trial and error, this video will help many newcomers to the hobby.
The issue is not explaining it, as that is relatively easy. It is just most novices have far better things to worry about messing with. That and devices like the ASIAIR do not let you adjust it.
Thank you Cuiv, it's good to have this valuable nugget of information. It's been ages now watching rain drops UK running down my windows. clear skies are rare as rocking horse poo💩💩.. So applying tips etc has now become more interesting than taking the light frames!!! 😂😂 Happy day & new year, thank you for all you do.. Atb Tom dull wet UK....
Merry Christmas. An excellent video as offset seems to be quite a mysterious topic out on the net and on the forums with a whole range of settings being offered without any real explanation as to why that number was settled on. Your video gives a nice explanation of how to calculate it with meaning. Thanks again and wishing you a great 2024 (hope we see some more paragliding videos too).
Hi there Geek. I recently bought the Altair Astro version (AA26C) and use Indi/Ekos + altair driver. My understanding is that when taking short exposure darks (BIAS frame) the histogram should not get cut off on the left. I think I saw this on a Sharpcap forum. In Indi oontrols my camera settings are Conversion Gain = High. High Full Well Mode = off. Low Noise Mode = off. Gain=100, Offset=50, exp=.001. The histogram using indi looks fine. Peak at 50, drops to zero below 25 and above 75. In NINA I get the Ultra Mode option same as you which up to now I had set to off. 12000 clipped pixels is microscopic compared to 24Million pixel on the sensor (5 parts in ten thousand). Not sure this makes that much difference for this camera, but great that you explain how to measure things. Should I be using Ultra Mode (NINA) / Low Noise Mode (indi) ? Confusing camera.
Interesting. Would like to see what the master lights look like at various offsets and how one setting might produce a better end result over the others. In PixInsight, you can set a minimum pedestal value during WBPP, which I'm not sure yields the same outcome.
Great video, thanks! I'm trying to get this right on my Altair 269C TEC, the range is a lot smaller 0-462 and NINA set the default to 16. Setting it higher, the Mean and Median go far too off and the difference is more than 1000, so it might have to do that it is a dual mode camera, or just a driver thing. Maybe I'll give SharpCap calibration a test, to see what values it shows. Love your channel and I can see how Japan has formed your kindness! ありがとう ございます
Finding the correct offset was always a thing for old-school QHY CCD cameras before finding the correct gain - something lost in the mists of time I guess. From my understanding set it once and never touch it again - I check offset/gain values every couple of years and they haven't moved.
Cuiv, I finally understand OFFSET. THANK YOU. ASI's offset is likely locked down like the rest of their stuff, at least within their System. I can't find ANY option to change the offset in any of their software. Am I correct? ☹
Merry Christmas. I just bought the same camera you have and was in doubt as to how the gain and offset values should be set. Thank you for the clarification 😊🎅
Aha… now the offset might be why my images looks pixelated when doing background extraction in Pixinsight. As some pixels turn absolutely black. 😮 Will experiment with the offset and hopefully get some clear whether to test in 2024.
Another great video. Are you taking super short exposure to set your offsets (I think you said .001)? I was taught when find the correct offset to use the same exposure time you would use to take your lights. I hope this is wrong, because it means that like Darks, you’ll need a separate offset value for each exposure time.
I was thinking the same thing, so I tested it with my 533mc pro. Fortunately, that’s not the case. At an offset of 10 my minimum value was around 235 at all exposure times. (001secs, 30secs, 2min, and 3mins) Only the max values went up.
Merry Christmas, Cuiv. This is the best, honest explanation I've seen for offset. I noticed you said you don't shoot darks anymore and I've read the read noise is so low, one doesn't need to shoot darks. I'm thinking you are using flats, dark flats, and bias to calibrate with. If yes, how are you taking bias frames. I've seen numerous posts about STOP taking bias on the CMOS cameras because setting the lowest exposure for the camera gives inconsistent subs. Are you using some rule-of-thumb for arriving at the exposure time? Whew, sorry for several questions.
The practice of using dark flats instead of bias frames came about largely because of the Panasonic sensor in the ASI1600 that produced bias signal that varied with exposure length (I think it changed gain modes below 0.2s or something like that). AFAIK the IMX571/455 don't have this issue. If you use dark flats to calibrate your flats you don't need to use bias frames at all, as long as you use uncalibrated darks (i.e. do not use scaled darks). The (uncalibrated) master dark contains the bias signal and will remove it from the lights. The (uncalibrated) flat darks contain the bias signal and will remove it from the flats. If you use an adjustable flat panel you can take all your flats at the same exposure, then you just need a master flat dark at that length to calibrate out bias (a single one will work for all filters, of course, since it's just a dark frame). You can get weirdness with some flat panels and rolling shutter cameras if you go too short, but typically anything over about 1 sec should be fine. As far as not using darks that's a personal choice, dark current and DCNU is crazily low with the current sensors like the IMX571 and IMX455, but it's not zero. I still calibrate with them, it matters more when imaging very dark objects with very long exposures (I often shoot 30-45 min in narrowband) and stretching hard. You only need to generate the master dark once after all (well, and maybe update periodically). To my mind, if you are bothering to calibrate with bias frames but not darks, you might as well just use a master dark and thus do a better calibration.
At minus ten degrees on the IMX571, the dark current mean is 0.15 electrons for a 300s exposure. Negligible compared to read noise mean or shot noise. These days I take 1 second "bias" frames because at -10C functionally a 1 second frame and a 0.001s frame are the same (dark current is 0.00049 electrons in 1 second exposure). My flats are 1-2s long. Add to that the lack of amp glow. So I don't bother with dark frames :)
@@paths1111 I wasn't aware that the IMX571 didn't suffer from the same issue as the sensor in my older ASI 1600. I'm used to shooting darks, flats and dark flats. I never scale my darks. I just recently got an adjustable flat panel so I'll have to incorporate the same exposure on flats to allow for a single master dark flat. Thanks
@@CuivTheLazyGeek Ahh ok. I haven't tried that method without darks. I can see how this would be of benefit for my LRGB images where my exposure times are typically under 300 seconds. Some new things to try out whenever the clouds leave. Thanks.
Not looking forward to trying to balance offset and gain against sub lengths and filling well capacity. Is there a way to do this in just nina? Do you have a video how to? :) Ive watched you video on optimum exposure times, ill watch it again ;)
Thanks for this video. I'm also using an IMX 571 camera (QHY 268C). As you said the behavior will depend on the read mode and gain, but will the values be dependent on sensor temp too?
How about EAA? In EAA, there is no post processing involved. Does the offset matter there? For EAA we usually use higher gain because we do short exposures (15s -30s max). We rather observe the object, than collect data for it for later post processing. We are observing only through live stacked images.Does all that apply to EAA to? On my 178MC U usually do 30s exposures and have my gain set to 150, Could someone recommend a good offset for that camera keeping EAA in mind and not post processing?
Great video Cuiv! Merry X'mas to you and the family! I've been using 50 by default for the past 4 yrs too! How does this offset then play together with PixInsight's WBPP pedestal? I've been using WBPP's pedestal of 100 instead of pushing the baseline up.
Thanks Sean! But if you're using ZWO, an offset of 50 actually means 500 ADU in the ZWO world as I understand it (in which case you are fine!). Afaik, Pedestal in PixInsight will help lights not have dark pixels after bias subtraction. But if your offset was too low, your bias frames was bad/not enough info in the first place so PI can't do anything about that
Oh phew, good to know that ZWO has a different way of interpreting ADU :p. OK so the PI WBPP Pedestal is just another layer above that. Nothing beats at the h/w level first :D!
Excellent video, thanks a lot, and Merry Christmas to you! I am wondering how meaningful the question of offset is for modern DSO cameras. How much difference did it make for you to bump the offset from 50 to 200 on the touptek, visually or by direct measurement of noise? I am asking because with the default offset of 50, you get only 13K pixels at 0, out of 26M pixels. That is only 0.05% of the pixels. Also, both mean and median are 54 indicating a very tight distribution with a long but very thin tail. This is a far cry from older sensors that used to have a lot of structure in the bias frames.
That number could potentially increase quite a bit due to the way the ADU counting statistics combine during image calibration. Granted the impact will be more noticeable in nosier (albeit mainly 16-bit) CCD sensors but 5 minutes spent preventing a problem a single time is easier than fixing after the fact. Theoretically the problem during calibration will get progressively worse as the bit-depth decreases moving to 14-bit and then 12-bit cameras (that includes older and some not-so-old CMOS cameras) so Cuiv's 16-bit camera will be better than most.
At minus ten degrees on the IMX571, the dark current mean is 0.15 electrons for a 300s exposure. Negligible compared to read noise mean or shot noise. These days I take 1 second "bias" frames because at -10C functionally a 1 second frame and a 0.001s frame are the same (dark current is 0.00049 electrons in 1 second exposure). My flats are 1-2s long. Add to that the lack of amp glow. So I don't bother with dark frames :)
Cuiv, most logical and rational method I have seen for setting offset. Nice one mate. One other small point is that yet again NINA gives us astrophotographers all the tools we need.
I did mine last year in SharpCap and ended up with a value of 6 on my ASI585, but the offset only ranges from 0-200 on this camera. I thought I'd give it a shot with this method just now and I think it was pretty close, but I'll probably bump it up by a whole digit to 7. I found that the numbers change a lot if I loop my images in NINA though; for me at 1*e-5s it goes like: 0(x1), 40(x2) , (0(x1), (160(x1), (128(x3), (0(x1)... And at 7 everything is just a little bit higher, I still hit a few 0s, but less frequently. I found the SharpCap method to be a bit "hacky", and I was never quite sure if it was correct, but I think I like this NINA method a bit better because you get to see the real numbers, plus it's additional confirmation that I was in the right ballpark. I think the default in the ZWO driver for my camera was originally 25, which was far too high!
If you like and subscribe the bandpass of your filters will go down to 2,5 nm. Also your guiding RMS will never exceed 0.1. True story*. 💪👍 *not really true, but it will feel like it. Possibly.
This video is a good opportunity to again say thank you for your commitment to astrophotography and to your viewers. Your explanations make sometimes complicated topics understandable, and your sense of humor makes your channel a welcome place to be. Merry Christmas Cuiv.
I have made the mistake of running too low of an offset.. and the raw images looked great considering my bright skies.... but...but!!! they were totally un-calibratable lmfao. terrible mistake
So for my IMX571 and IMX585 cameras I basically use the following with the sensor cooled to -10C - 1s long bias frames (1s is pretty much the same as 0.0001s at that temperature) - 1-2s flat frames I use this to calibrate all my frames regardless of length and I don't bother with dark frames.
Merry Christmas, Cuiv, and thanks for another great video. Interesting to see how different manufacturers using the same sensors, apply their firmware/electronics differently. In your Touptec camera, apparently 1 offset equals 1 ADU. For QHY this is 16 ADU, and for ZWO this is 40 ADU. So correct offset values between cameras differ a lot. Also, the Touptec apparently can report a ‘0’ value, whereas QHY and ZWO cameras report ‘1’ as the minimum value, or ‘4’ if it is a 14-bit camera.
Hi Cuiv! As always, thank you for all your useful tips! What would you do with an ASI294 MC-Pro and it's problems with inconsistent low exposure shots? Is this method viable to understand the correct offset or should I go up to 2+ seconds shots? Regards!
@@CuivTheLazyGeek thank you for the response! I've already tried both "bias" timings and "darkflat" timings and the difference is almost negligable for this test. To be sure I've used 3 seconds exposures and got a final value for my offset of 4 (in ZWO terms). The default value for the "unity gain" in the drivers is usually 6, so I'm surprised! I've always used 30 offset and I wil ltry with 4 my next session! Thank you again Cuiv!
Hi Cuiv! Great and informative video👍 I've just tried this metod with my asi533mc-p, at -10 C degrees, gain 100 and I've got the offset of 7 to be about right(with minimun of 80 and mean of 230). But is it okay that the calculated offset is so low for this type of sensor ?
Hey Cuiv, great video as always! very informative :) Im curious if I did something wrong tho, my ( ASI 294mm bin1) offset @ gain 0 comes to about 5, isn't that pretty low? I couldn't test it yet unfortunately...
I followed this method on my ASI6200MC and determined the optimal offset is 15 at gain 0. My minimum pixel value on bias frames is 9 at those settings.
At minus ten degrees on the IMX571, the dark current mean is 0.15 electrons for a 300s exposure. Negligible compared to read noise mean or shot noise. These days I take 1 second "bias" frames because at -10C functionally a 1 second frame and a 0.001s frame are the same (dark current is 0.00049 electrons in 1 second exposure). My flats are 1-2s long. Add to that the lack of amp glow. So I don't bother with dark frames :)
Cuiv, Interesting Video. However, I have an issue. The video seems to be a some what comparison between the ZWO-ASI2600mm and the Touptek/RisingCam 2600mono camera as they both use the following sensor: SONY IMX571 CMOS. Accordingly, they supplied information on the specifications of the camera, for the vendor to select functions that they wish to pass on to the consumer. It appears that ZWO seem to have gone out of their way to make it easier for the consumer in calculating the optimum gain and offset, known as 'Unity Gain'. Also allowing the user to have the ability to select a manual option and set values of their choosing. All good so far. So here is my issue. You have a Touptek camera and set your 'Gain' to 100 (101),'Offset' to be 151. Using the short Bias exposure to calculate values for the 'Min (0)' and 'Max (65536)' Pixel values. I don't see a problem with this, other than the values you have defined as correct for your camera. It appears to me that you are using the ZWO 'Unity Gain 100' as the starting point gain for the Touptek camera. I know the Touptek Min gain is 100, which is just a coincidence compared to the ZWO 100 optimum gain. So my point is this. Taking that ZWO has calculated the 'Unity Gain' correctly, and we can probably assume they have, and we need a comparison of the two, as Touptek, as I know, does not supply a unity gain value, then the following formula would need to be applied. The ZWO has a gain value of 0 to 450. The Touptek has a gain value of 100 to 10,000. Note: Values under 100 cannot be selected. So, if one needs to take a direct comparison between the two cameras to find the gain for the Touptek, the following calculation would need to apply. Touptek's max gain is 10,000. We would divide this with ZWO's max gain of 450. This would give a value of 22.2222. We would multiply 22.222 by ZWO's Unity Gain of 100, and would give a value of 2222. This value would be equivalent to the ZWO Unity Gain of 100. So the unity gain for the Touptek would be 2222. Formula: 10000/450=22.2222 22.2222x100=2222 Touptek max Offset is 7936. We would divide this with ZWO's max Offset 240. This would give a value of 33.06. We would multiply 33.06 by ZWO's Unity Offset of 75, and would give a value of 2479. This value would be equivalent to the ZWO Unity Offset of 75. So the unity offset for the Touptek would be 2479. Formula: 7936/240=33.06 33.06x75=2479 UNITY GAIN ZWO GAIN 0 100 450 Touptek GAIN 100 2222 10000 UNITY OFFSET ZWO Offset 0 75 240 Touptek 0 2479 7936 I have ignored LCG, HCG etc. as we are only finding a comparison unity between the ZWO and Touptek. I have always used the above gain at 120s for my Touptek/RisingCam camera as I found 100 did not work too well even with the above activated. I am not all that concerned about a few black pixels or over bright ones, as this depends on the target anyway. I am in a high bortle zone 7 and getting worse. So what is your opinion? Is it that we have been used to values of ZWO and think these values also apply to all other cameras, such as Touptek. ------------
I just did this test with my ASI533MCPRO in dark closet camera cap on and inside a dark box so absolutely dark and 101gain with an offset of 5 as per sharpcap sensor analysis recommendation. Why is my min at 12 @1pixel then changed to 20, then 0, then 16@3x I left it on a loop to take exposures of 0.0001
Dude... this video, and your channel as a whole, is SO informative and straightforward. I sincerely appreciate your demonstration of each step you take and what it all means and why you do different things. One question I have... you mentioned that you don't use dark frames any more. Can I ask why? I am new to astrophotography, but I thought dark frames were essential to getting the best images?
Hi. I trief this and it simply did not work. I have a QHY 268 C set on dso mode gain 30 offset 83. No matter where I set offset I am unable to get the min adu off 0 and it always shows 16000 clipped pixels. The max adu shows just barely more then the mean/median and never shows more then one or two white clips. And the offset value does not have the relationship to mean/median as in your video. I have been using offset 83 and in Nina this shows a mean/ median off about 1350. Also.. the mean and median do not change significantly from these values when I take say 60 sec lights. Any advice you can share to help me with this ??
Thank you for this precious information. I just checked the offset value of my camera and I saw that it is 0. Shit !!! I had no idea about this. I've had the QHY 294m pro for almost 2 years and couldn't get the detail I wanted. Instead I had a lot of noise even though I was taking calibration frames. Do you think this is the main cause of the problem ? I feel frustrated but luckily I saw your video and will fix it now. Thank you again !
I am watching this video for the second time and I have a question in order to help me further understand in the example the exposures are 0001 sec but what if is as taking say 6 sec exposures wouldn't my min reflect higher since I'm using a much higher exposure? Say I was using gain 101 and offset of 70 and min at 6 sec exposure show as 2000+
One more comment, and a question. I do not see any settings other than Default Gain, and Create 32-bit data under my camera settings. Like I said, I have an OGMA camera, which I think is made by the same people who make your camera. There are settings under the Gear Icon at the top of that page, when I click on it, but none are Offset. Now I am not seeing Offset in Sequencer either. I was seeing it before!! I am using the 3.0 Beta version of NINA. Beta003. Thanks for any advice! Mark
Happy Christmas Cuiv. Good explanation of this setting. I have been leaving the offset on my mono and OSC cameras at default settings as the images seem to be ok. Will try adjusting the offset the next time I get a clear night ( have only had three in the last two months )
Thanks for the tutorial !. So you set the offset high enough to avoid zeroes. Makes sense. Curious what then happens to the repeatability of pixels in dark frames and if that 'image' helps to characterize/process images. Is there a test object to help set gain also ?
Not all cameras calculate the offset the same. My ASI2600mm used a default of 50 and that gives a mean bias of 500 ADU. I have it reduced to 30 and that gives 300 ADU.
The issue I see is the histogram values are near 10X the offset value. ZWO may be doing things different, but it looks like be a software bug. I can set my offset to 18 and have zero dark pixels but then the histogram Mean and Median values are near 180. For now, I am leaving it at 50 since the histogram Min value 323 (2x).@@davidkennedy3050
Merry Christmas Cuiv! Back in the long, long ago there was an article from Dr. Craig Stark (original author of PHD Guiding) that described the process for CCD cameras. When I got into CMOS cameras I read Dr. Q's article (QHYCCD) that described the same process you go over here. I basically read his article and followed the same process you highlight here. It does help to optimize your dynamic range which helps minimize frustration in imaging from Bortle 9 zones like I am in near Dallas, Texas, USA. One of these days I need to take my daughter to Tokyo so she can meet her Japanese relatives.
Hey Cuiv! Thanks for these videos! I'm still a little confused though... Does all of this make any sense if absolutely 0 pixel of your lights frames has a 0 value? Would it still help for stretching and all?
@CuivTheLazyGeek Thanks for all your insights, I appreciate them all as an Astro noob. I don't know how you do it? I mean keeping your wife😃 I lost mine a few years back in another rabbit hole called Euro Rack😂 At least now the only one I can lose in the black rabbit hole is myself😅 Merry Christmas and Happy New Year🎄🌌🌠🥂
I am not involved with astrocams but are you sure that an additional offset of "only 32" is unimportant? I thougt you have to handle these numbers on a logarithmic scale - so 32 = 2 powered by 5 that means you have lost 5 bits! Maybe I am wrong ??
Finally someone answers my question on Offset. I have seen it on NINA, in the sequencer, and never knew where to set it, or what to set it too. I have the OGMA AP26CC camera now, which I think is the same as the Topek ?? that you have, with the Sony 571 chip. I love the camera, but this will really help me get the maximum performance from it. Thank you very much for making this video. I really love NINA as well, but wish I knew how to use it better. Thanks for this, and many of your other videos...all very helpful. Mark
Merry Christmas! Yes, a lot of people afraid to use a high offset, somehow the loss of dynamic range scares people I guess, but seeing images from people their loss of DR is more contributed to incorrect processing and I'm guilty of that too. I would say on average; without careful image editing; people ruin their DR in their image by cutting as much as many thousands of ADU steps, compared to a few hundreds that a higher offset would do. The loss of DR with the offset just irrelevant and minuscule, compared to wrong image editing habits. I just follow how ZWO set it in Asiair, (offset 75 for zwo cameras) and seeing how that's like almost halfway up on the offset scale, I imitate it to do similar with my non-zwo cameras and I am perfectly fine losing a few hundred or even a 1000 DR steps due to high offset. Otherwise Pixinsight will report me that it had to do a "huge pedestal" correction when processing and that lets me know that I did use the wrong offset.
I love the work you do and your contribution to AP. I have a RASA11 and I am worried about doing a "tilt correction". Please consider a review of this factor and how to do the procedure.
Thanks Steve! Tilt is one of those things I have never had success with - and imo unless someone is using full frame and a Tak, it may not be worth the effort... Right now I'm definitely not qualified to make such a video unfortunately!
Thanks for the video! Appreciate the insight. Wanted to know if the offset process you described is target independent? In other words, once this has been set, one does not need to change it ever again?
I measure the sky brightness around my target with Sharpcaps smart histogram brain function. Assuming you have previously performed a sensor analysis ( only need to perform this once) Sharpcap with work out your offset, optimal gain, sub length, exposure etc. I mean how easy was that?
Thanks, Cuiv now I know how to check the offset. My ZWO ASI2600MC Duo default offset is also 50 but this gives the histogram Mean and Median values near 500. For any offset the Mean and Median histogram values near 10X the offset. UPDATE Looking at the fits header, NINA is added 50 as the offset not the 500 being added my ZWO.
Merry Christmas ‘tis like a present under the astrophotography tree! Now that I’m starting to use MeleQ in addition, this is quite relevant. Re. ASIAIR, I heard ZWO ASIAIR set an offset of 45 or so to the 2600 at 101 gain…but I need to look again on Cloudy Night! I will read through the comments here too.🎉❤
Yep it seems the ASIAir hides the offset and sets it to a suitably high value to make it easier to the end user! And their offset units are different from what I heard
My Patreon: www.patreon.com/cuivlazygeek
Here is an EXCELLENT explainer by Dale Ghent, one of the NINA developers: daleghent.com/2020/08/understanding-camera-offset
My videos on gain, etc: ua-cam.com/video/GKXkM_FbFgg/v-deo.html and ua-cam.com/video/SYQ1i4k62eI/v-deo.html
Amazon affiliate: amzn.to/3hTB5Ne
Agena affiliate: bit.ly/3Om0hNG
High Point Scientific affiliate: bit.ly/3lReu8R
All-Star Telescope affiliate: bit.ly/3SCgVbV
Dwarf 2 Smart Telescope: bit.ly/3SyChXu
Seestar S50: tinyurl.com/3n62hpzx
Two problems with making a video on 25th December are the fact that for at least 364 days of the year, people will be watching on the wrong day for you to greet them as you did. And of course countless millions of people don't celebrate the day.
Nonetheless, thank-you for your thoughts and for the video. 🙂👍
That histogram would be more useful if it could be switched to a logarithmic wavelength display. That would spread the low end for you, if the software has that facility,
What I have learned is that you should always make sure your histogram is as far away from the left side of the histogram as possible to prevent clipping since what we image is so faint. Because this is a linear RAW image that will be stretched later, don't worry about the peak being too far to the right as long as it does not exceed the 1/3 of the histogram as we can fix this with the histogram stretch in post processing. Already messed up and imaged at zero offset? Don't throw those frames away, you can add a pedestal when you integrate. Yes you lost data but you can still process your image. And yes whatever you change whether it be the gain, offset, temperature, and even the USB limit (yes that can cause issues too like banding!) take new calibration frames. Thanks for making this important video Cuiv and Happy Holidays!
I breathed a sigh of relief after checking some old bias files. With a gain of 120 and an offset of 50 on my ASI294MC pro, it appears that I've been doing it right, more or less. Thanks for the clear explaination of what offset is all about.
Great to know!
@@CuivTheLazyGeek I should mention that I don't take biases everytime I shoot. In fact, I just subtract off the bias value when I do my stacking in SIRL--supposedly less noise added to the result.
@@richardshagam8608 having a bias library you keep reusing is fine, I do the same :)
But what do you mean by "you just subtract off the bias value when you do your stacking"?
Great video Cuiv. When I started this hobby back in 2021, I searched for answers to the mysterious offset, it seemed no one wanted to talk about it or if they did it was "yeah just set it at 50". I finally figured it out on my own, after much trial and error, this video will help many newcomers to the hobby.
Thanks William, thanks for your support, and Merry Christmas!
The issue is not explaining it, as that is relatively easy. It is just most novices have far better things to worry about messing with. That and devices like the ASIAIR do not let you adjust it.
Thank you Cuiv, it's good to have this valuable nugget of information. It's been ages now watching rain drops UK running down my windows. clear skies are rare as rocking horse poo💩💩.. So applying tips etc has now become more interesting than taking the light frames!!! 😂😂 Happy day & new year, thank you for all you do.. Atb Tom dull wet UK....
Hope you get clear skies soon!
Merry Christmas. An excellent video as offset seems to be quite a mysterious topic out on the net and on the forums with a whole range of settings being offered without any real explanation as to why that number was settled on. Your video gives a nice explanation of how to calculate it with meaning. Thanks again and wishing you a great 2024 (hope we see some more paragliding videos too).
Glad it is helpful! Merry Christmas!
Hi there Geek. I recently bought the Altair Astro version (AA26C) and use Indi/Ekos + altair driver. My understanding is that when taking short exposure darks (BIAS frame) the histogram should not get cut off on the left. I think I saw this on a Sharpcap forum.
In Indi oontrols my camera settings are Conversion Gain = High. High Full Well Mode = off. Low Noise Mode = off. Gain=100, Offset=50, exp=.001.
The histogram using indi looks fine. Peak at 50, drops to zero below 25 and above 75.
In NINA I get the Ultra Mode option same as you which up to now I had set to off.
12000 clipped pixels is microscopic compared to 24Million pixel on the sensor (5 parts in ten thousand).
Not sure this makes that much difference for this camera, but great that you explain how to measure things.
Should I be using Ultra Mode (NINA) / Low Noise Mode (indi) ? Confusing camera.
Interesting. Would like to see what the master lights look like at various offsets and how one setting might produce a better end result over the others. In PixInsight, you can set a minimum pedestal value during WBPP, which I'm not sure yields the same outcome.
Great video, thanks! I'm trying to get this right on my Altair 269C TEC, the range is a lot smaller 0-462 and NINA set the default to 16. Setting it higher, the Mean and Median go far too off and the difference is more than 1000, so it might have to do that it is a dual mode camera, or just a driver thing. Maybe I'll give SharpCap calibration a test, to see what values it shows.
Love your channel and I can see how Japan has formed your kindness! ありがとう ございます
Wonderful. Thank you so much🙏😘
Does it mean,that I I set the perfect off set, than I don't have to run a cosmetic correction for cold pixels?
Finding the correct offset was always a thing for old-school QHY CCD cameras before finding the correct gain - something lost in the mists of time I guess. From my understanding set it once and never touch it again - I check offset/gain values every couple of years and they haven't moved.
Merry Christmas Quiv! You’ve solved yet another mystery setting for me - so invaluable - many thanks!
Happy holidays! Glad to help!
Merry Christmas Cuiv! - I've learned alot from you over the year. Thanks for doing what you do!
Happy holidays!
Cuiv, I finally understand OFFSET. THANK YOU. ASI's offset is likely locked down like the rest of their stuff, at least within their System. I can't find ANY option to change the offset in any of their software. Am I correct? ☹
Merry Christmas. I just bought the same camera you have and was in doubt as to how the gain and offset values should be set. Thank you for the clarification 😊🎅
Happy holidays! And glad to help :)
So helpful Cuiv. This was exactly what I needed right now. Thanks
Glad it helped!
Merry Christmas Cuiv! Thank you for all the great information you share with us!
Happy holidays!
Can you do like a test with some nerrowband filters?
Aha… now the offset might be why my images looks pixelated when doing background extraction in Pixinsight. As some pixels turn absolutely black. 😮
Will experiment with the offset and hopefully get some clear whether to test in 2024.
Another great video. Are you taking super short exposure to set your offsets (I think you said .001)? I was taught when find the correct offset to use the same exposure time you would use to take your lights. I hope this is wrong, because it means that like Darks, you’ll need a separate offset value for each exposure time.
I was thinking the same thing, so I tested it with my 533mc pro. Fortunately, that’s not the case. At an offset of 10 my minimum value was around 235 at all exposure times. (001secs, 30secs, 2min, and 3mins) Only the max values went up.
Great video Cuiv ! Thank you a lot ! Now I know how😀
Happy to help!
Amazing Esoteric Info, Cuiv! You are the bomb!
Merry Christmas to you too.
🧑🏻🎄
Wow! I knew the basics, but this is really helpful!
Glad it was helpful!
Merry Christmas, Cuiv. This is the best, honest explanation I've seen for offset. I noticed you said you don't shoot darks anymore and I've read the read noise is so low, one doesn't need to shoot darks. I'm thinking you are using flats, dark flats, and bias to calibrate with. If yes, how are you taking bias frames. I've seen numerous posts about STOP taking bias on the CMOS cameras because setting the lowest exposure for the camera gives inconsistent subs. Are you using some rule-of-thumb for arriving at the exposure time? Whew, sorry for several questions.
The practice of using dark flats instead of bias frames came about largely because of the Panasonic sensor in the ASI1600 that produced bias signal that varied with exposure length (I think it changed gain modes below 0.2s or something like that). AFAIK the IMX571/455 don't have this issue. If you use dark flats to calibrate your flats you don't need to use bias frames at all, as long as you use uncalibrated darks (i.e. do not use scaled darks). The (uncalibrated) master dark contains the bias signal and will remove it from the lights. The (uncalibrated) flat darks contain the bias signal and will remove it from the flats. If you use an adjustable flat panel you can take all your flats at the same exposure, then you just need a master flat dark at that length to calibrate out bias (a single one will work for all filters, of course, since it's just a dark frame). You can get weirdness with some flat panels and rolling shutter cameras if you go too short, but typically anything over about 1 sec should be fine. As far as not using darks that's a personal choice, dark current and DCNU is crazily low with the current sensors like the IMX571 and IMX455, but it's not zero. I still calibrate with them, it matters more when imaging very dark objects with very long exposures (I often shoot 30-45 min in narrowband) and stretching hard. You only need to generate the master dark once after all (well, and maybe update periodically). To my mind, if you are bothering to calibrate with bias frames but not darks, you might as well just use a master dark and thus do a better calibration.
At minus ten degrees on the IMX571, the dark current mean is 0.15 electrons for a 300s exposure. Negligible compared to read noise mean or shot noise.
These days I take 1 second "bias" frames because at -10C functionally a 1 second frame and a 0.001s frame are the same (dark current is 0.00049 electrons in 1 second exposure). My flats are 1-2s long.
Add to that the lack of amp glow. So I don't bother with dark frames :)
@@paths1111 I wasn't aware that the IMX571 didn't suffer from the same issue as the sensor in my older ASI 1600. I'm used to shooting darks, flats and dark flats. I never scale my darks. I just recently got an adjustable flat panel so I'll have to incorporate the same exposure on flats to allow for a single master dark flat. Thanks
@@CuivTheLazyGeek Ahh ok. I haven't tried that method without darks. I can see how this would be of benefit for my LRGB images where my exposure times are typically under 300 seconds. Some new things to try out whenever the clouds leave. Thanks.
Thanks!
Wow thanks for the support! Merry Christmas!
Not looking forward to trying to balance offset and gain against sub lengths and filling well capacity. Is there a way to do this in just nina? Do you have a video how to? :) Ive watched you video on optimum exposure times, ill watch it again ;)
Merry Christmas Cuiv
Nicely done and Merry Christmas!
Thanks! You too!
How hard would it be for manufacturers to put a black line on the outside of the camera to mark the front of sensor ?
That would just be too convenient!
Useful video Cuiv. Thanks
Thanks for the information! Well done.
great video. Definitely going to do this now...!
Have fun!
Thanks for this video. I'm also using an IMX 571 camera (QHY 268C). As you said the behavior will depend on the read mode and gain, but will the values be dependent on sensor temp too?
In theory it shouldn't depend on temp, but if you use different temps, better to check!
Merry Christmas!
Thank you, this is really helpful!
How about EAA? In EAA, there is no post processing involved. Does the offset matter there?
For EAA we usually use higher gain because we do short exposures (15s -30s max). We rather observe the object, than collect data for it for later post processing.
We are observing only through live stacked images.Does all that apply to EAA to?
On my 178MC U usually do 30s exposures and have my gain set to 150, Could someone recommend a good offset for that camera keeping EAA in mind and not post processing?
Shouldn't matter much for EAA to be honest
Great video Cuiv! Merry X'mas to you and the family! I've been using 50 by default for the past 4 yrs too! How does this offset then play together with PixInsight's WBPP pedestal? I've been using WBPP's pedestal of 100 instead of pushing the baseline up.
Thanks Sean! But if you're using ZWO, an offset of 50 actually means 500 ADU in the ZWO world as I understand it (in which case you are fine!).
Afaik, Pedestal in PixInsight will help lights not have dark pixels after bias subtraction. But if your offset was too low, your bias frames was bad/not enough info in the first place so PI can't do anything about that
Oh phew, good to know that ZWO has a different way of interpreting ADU :p. OK so the PI WBPP Pedestal is just another layer above that. Nothing beats at the h/w level first :D!
This is super helpful, thank you!! Does anyone know where I could do this in Stellarmate/Ekos?
No good stats in SM yet, I used the PixInsight statistics tool instead (make sure the check the "unclipped values" checkbox)
Do you think the trial version would be sufficient to do this?
Excellent video, thanks a lot, and Merry Christmas to you! I am wondering how meaningful the question of offset is for modern DSO cameras. How much difference did it make for you to bump the offset from 50 to 200 on the touptek, visually or by direct measurement of noise?
I am asking because with the default offset of 50, you get only 13K pixels at 0, out of 26M pixels. That is only 0.05% of the pixels. Also, both mean and median are 54 indicating a very tight distribution with a long but very thin tail. This is a far cry from older sensors that used to have a lot of structure in the bias frames.
Merry Christmas! I haven't been able to validate yet, but hey I'll take fewer clipped pixels any day :)
That number could potentially increase quite a bit due to the way the ADU counting statistics combine during image calibration. Granted the impact will be more noticeable in nosier (albeit mainly 16-bit) CCD sensors but 5 minutes spent preventing a problem a single time is easier than fixing after the fact. Theoretically the problem during calibration will get progressively worse as the bit-depth decreases moving to 14-bit and then 12-bit cameras (that includes older and some not-so-old CMOS cameras) so Cuiv's 16-bit camera will be better than most.
Hello. I have the same camera from Touptek. Is the Gain 100 Offset 50 setting the best? Greetings
No - watch the video :)
Question, Why do you not use dark frames anymore? Are you using Dark Flats instead?
No amp glow on these modern sensors is my best bet
At minus ten degrees on the IMX571, the dark current mean is 0.15 electrons for a 300s exposure. Negligible compared to read noise mean or shot noise.
These days I take 1 second "bias" frames because at -10C functionally a 1 second frame and a 0.001s frame are the same (dark current is 0.00049 electrons in 1 second exposure). My flats are 1-2s long.
Add to that the lack of amp glow. So I don't bother with dark frames :)
No nina No sharcap No ASCOM!!!!
ASIAIR users over hear like Off-what? As of now I don’t think it’s adjustable in the ZWO ecosystem 😢
Offset defaults on ZWO work well though.
Yep it seems the ASIAir hides the offset and sets it to a suitably high value to make it easier to the end user!
what? no darks ? will you share your magic trick for no darks?
Just did! :)
LOL I asked last night and this morning I seen the vedio thaks Cuiv@@CuivTheLazyGeek
I ask and wow you are fast! LOL @@CuivTheLazyGeek
Cuiv, most logical and rational method I have seen for setting offset. Nice one mate. One other small point is that yet again NINA gives us astrophotographers all the tools we need.
NINA is awesome :)
Thanks!
Thanks for your support!!
That was a smooth Like, Comment, Subscribe moment. 🙂 Hope that you're having a nice bucket of KFC today!
Hahaha KFC, THE Christmas food in Japan :)
Of course you were doing things wrong if your lazy it's to be expected lol.
no real ability to set offset using the Asiair plus right? At least I haven't seen any provisions to make adjustments if needed.
I did mine last year in SharpCap and ended up with a value of 6 on my ASI585, but the offset only ranges from 0-200 on this camera. I thought I'd give it a shot with this method just now and I think it was pretty close, but I'll probably bump it up by a whole digit to 7.
I found that the numbers change a lot if I loop my images in NINA though; for me at 1*e-5s it goes like: 0(x1), 40(x2) , (0(x1), (160(x1), (128(x3), (0(x1)...
And at 7 everything is just a little bit higher, I still hit a few 0s, but less frequently.
I found the SharpCap method to be a bit "hacky", and I was never quite sure if it was correct, but I think I like this NINA method a bit better because you get to see the real numbers, plus it's additional confirmation that I was in the right ballpark.
I think the default in the ZWO driver for my camera was originally 25, which was far too high!
If you like and subscribe the bandpass of your filters will go down to 2,5 nm. Also your guiding RMS will never exceed 0.1. True story*. 💪👍
*not really true, but it will feel like it. Possibly.
Hahahaha this is accurate! Thanks for the support 😊
This video is a good opportunity to again say thank you for your commitment to astrophotography and to your viewers. Your explanations make sometimes complicated topics understandable, and your sense of humor makes your channel a welcome place to be. Merry Christmas Cuiv.
I appreciate that! Thank you! And (belated) merry Christmas!
But what does this mean for ASIAir users who do not have the option to adjust offset?
I have made the mistake of running too low of an offset.. and the raw images looked great considering my bright skies.... but...but!!! they were totally un-calibratable lmfao. terrible mistake
Yep, it happens. Flat calibration in particular can suffer since the bias frames then don't contain the whole bias signal.
Hi , which is work for a 0.001s exposure time is also right for 300s ?
So for my IMX571 and IMX585 cameras I basically use the following with the sensor cooled to -10C
- 1s long bias frames (1s is pretty much the same as 0.0001s at that temperature)
- 1-2s flat frames
I use this to calibrate all my frames regardless of length and I don't bother with dark frames.
Merry Christmas, Cuiv, and thanks for another great video. Interesting to see how different manufacturers using the same sensors, apply their firmware/electronics differently. In your Touptec camera, apparently 1 offset equals 1 ADU. For QHY this is 16 ADU, and for ZWO this is 40 ADU. So correct offset values between cameras differ a lot. Also, the Touptec apparently can report a ‘0’ value, whereas QHY and ZWO cameras report ‘1’ as the minimum value, or ‘4’ if it is a 14-bit camera.
Okay ASIAIR, let us set OFFSETs now please!
Apparently no need to bother about it on the ASIAir, it's set automatically to a good value
Hi Cuiv! As always, thank you for all your useful tips!
What would you do with an ASI294 MC-Pro and it's problems with inconsistent low exposure shots? Is this method viable to understand the correct offset or should I go up to 2+ seconds shots?
Regards!
Good point! While cooling to -10C or -15C, take a 3s exposure, it will be equivalent to a bias frame!
@@CuivTheLazyGeek thank you for the response! I've already tried both "bias" timings and "darkflat" timings and the difference is almost negligable for this test. To be sure I've used 3 seconds exposures and got a final value for my offset of 4 (in ZWO terms). The default value for the "unity gain" in the drivers is usually 6, so I'm surprised!
I've always used 30 offset and I wil ltry with 4 my next session! Thank you again Cuiv!
ASIAIR does not allow change of the offset. There are no options. Apparently, the offset is set internally by the ASIAIR to always = 50
Thank you!
Hi Cuiv! Great and informative video👍
I've just tried this metod with my asi533mc-p, at -10 C degrees, gain 100 and I've got the offset of 7 to be about right(with minimun of 80 and mean of 230). But is it okay that the calculated offset is so low for this type of sensor ?
Hey Cuiv, great video as always! very informative :)
Im curious if I did something wrong tho, my ( ASI 294mm bin1) offset @ gain 0 comes to about 5, isn't that pretty low? I couldn't test it yet unfortunately...
ZWO recommends a gain of 0 for my ASI6200MC when shooting DSO's. I can set my offset now to double that and pull out my clipped levels.
I followed this method on my ASI6200MC and determined the optimal offset is 15 at gain 0. My minimum pixel value on bias frames is 9 at those settings.
LITERALLY looking for this yesterday 😂 why no darks quiv? You dont use master darks either?
At minus ten degrees on the IMX571, the dark current mean is 0.15 electrons for a 300s exposure. Negligible compared to read noise mean or shot noise.
These days I take 1 second "bias" frames because at -10C functionally a 1 second frame and a 0.001s frame are the same (dark current is 0.00049 electrons in 1 second exposure). My flats are 1-2s long.
Add to that the lack of amp glow. So I don't bother with dark frames :)
Cuiv,
Interesting Video. However, I have an issue.
The video seems to be a some what comparison between the ZWO-ASI2600mm and the Touptek/RisingCam 2600mono camera as they both use the following sensor: SONY IMX571 CMOS.
Accordingly, they supplied information on the specifications of the camera, for the vendor to select functions that they wish to pass on to the consumer.
It appears that ZWO seem to have gone out of their way to make it easier for the consumer in calculating the optimum gain and offset, known as 'Unity Gain'.
Also allowing the user to have the ability to select a manual option and set values of their choosing.
All good so far.
So here is my issue. You have a Touptek camera and set your 'Gain' to 100 (101),'Offset' to be 151. Using the short Bias exposure to calculate values for the 'Min (0)' and 'Max (65536)' Pixel values.
I don't see a problem with this, other than the values you have defined as correct for your camera. It appears to me that you are using the ZWO 'Unity Gain 100' as the starting point gain for the Touptek camera.
I know the Touptek Min gain is 100, which is just a coincidence compared to the ZWO 100 optimum gain.
So my point is this.
Taking that ZWO has calculated the 'Unity Gain' correctly, and we can probably assume they have, and we need a comparison of the two, as Touptek, as I know, does not supply a unity gain value, then the following
formula would need to be applied.
The ZWO has a gain value of 0 to 450. The Touptek has a gain value of 100 to 10,000. Note: Values under 100 cannot be selected.
So, if one needs to take a direct comparison between the two cameras to find the gain for the Touptek, the following calculation would need to apply.
Touptek's max gain is 10,000. We would divide this with ZWO's max gain of 450. This would give a value of 22.2222. We would multiply 22.222 by ZWO's Unity Gain of 100, and would give a value of 2222.
This value would be equivalent to the ZWO Unity Gain of 100. So the unity gain for the Touptek would be 2222.
Formula:
10000/450=22.2222
22.2222x100=2222
Touptek max Offset is 7936. We would divide this with ZWO's max Offset 240. This would give a value of 33.06. We would multiply 33.06 by ZWO's Unity Offset of 75, and would give a value of 2479.
This value would be equivalent to the ZWO Unity Offset of 75. So the unity offset for the Touptek would be 2479.
Formula:
7936/240=33.06
33.06x75=2479
UNITY GAIN
ZWO
GAIN 0 100 450
Touptek
GAIN 100 2222 10000
UNITY OFFSET
ZWO
Offset 0 75 240
Touptek 0 2479 7936
I have ignored LCG, HCG etc. as we are only finding a comparison unity between the ZWO and Touptek.
I have always used the above gain at 120s for my Touptek/RisingCam camera as I found 100 did not work too well even with the above activated.
I am not all that concerned about a few black pixels or over bright ones, as this depends on the target anyway.
I am in a high bortle zone 7 and getting worse.
So what is your opinion? Is it that we have been used to values of ZWO and think these values also apply to all other cameras, such as Touptek.
------------
I just did this test with my ASI533MCPRO in dark closet camera cap on and inside a dark box so absolutely dark and 101gain with an offset of 5 as per sharpcap sensor analysis recommendation. Why is my min at 12 @1pixel then changed to 20, then 0, then 16@3x I left it on a loop to take exposures of 0.0001
Dude... this video, and your channel as a whole, is SO informative and straightforward. I sincerely appreciate your demonstration of each step you take and what it all means and why you do different things. One question I have... you mentioned that you don't use dark frames any more. Can I ask why? I am new to astrophotography, but I thought dark frames were essential to getting the best images?
Hi. I trief this and it simply did not work. I have a QHY 268 C set on dso mode gain 30 offset 83. No matter where I set offset I am unable to get the min adu off 0 and it always shows 16000 clipped pixels. The max adu shows just barely more then the mean/median and never shows more then one or two white clips. And the offset value does not have the relationship to mean/median as in your video. I have been using offset 83 and in Nina this shows a mean/ median off about 1350. Also.. the mean and median do not change significantly from these values when I take say 60 sec lights.
Any advice you can share to help me with this ??
Is minimum of 16 and just one pixel's good? Following your method it happend that my offset value is 66 :) Altair 269C
Thank you for this precious information. I just checked the offset value of my camera and I saw that it is 0. Shit !!! I had no idea about this. I've had the QHY 294m pro for almost 2 years and couldn't get the detail I wanted. Instead I had a lot of noise even though I was taking calibration frames. Do you think this is the main cause of the problem ? I feel frustrated but luckily I saw your video and will fix it now. Thank you again !
I am watching this video for the second time and I have a question in order to help me further understand in the example the exposures are 0001 sec but what if is as taking say 6 sec exposures wouldn't my min reflect higher since I'm using a much higher exposure? Say I was using gain 101 and offset of 70 and min at 6 sec exposure show as 2000+
One more comment, and a question. I do not see any settings other than Default Gain, and Create 32-bit data under my camera settings. Like I said, I have an OGMA camera, which I think is made by the same people who make your camera. There are settings under the Gear Icon at the top of that page, when I click on it, but none are Offset. Now I am not seeing Offset in Sequencer either. I was seeing it before!! I am using the 3.0 Beta version of NINA. Beta003. Thanks for any advice! Mark
Happy Christmas Cuiv. Good explanation of this setting. I have been leaving the offset on my mono and OSC cameras at default settings as the images seem to be ok. Will try adjusting the offset the next time I get a clear night ( have only had three in the last two months )
Happy holidays! Have fun adjusting the offset!
Hmm I have a problem here, if I change my default offset and go to imaging it automatically goes back to default offset (100) whats going on here
Thanks for the tutorial !. So you set the offset high enough to avoid zeroes. Makes sense. Curious what then happens to the repeatability of pixels in dark frames and if that 'image' helps to characterize/process images. Is there a test object to help set gain also ?
Is it also possible to check the pixels in Pixinsight? If yeas which feature?
For Asi Air users, there seems to be no offset options - what do we do beyond making sure the histrogram is separated on the left?
Not all cameras calculate the offset the same. My ASI2600mm used a default of 50 and that gives a mean bias of 500 ADU. I have it reduced to 30 and that gives 300 ADU.
Same with my ZWO ASI2600MC Duo. I sent an email to ZWO. This may be a driver issue.
@@bobbryant4410 There is no issue. Just use a Bias just like Cuiv did to see what ADU the offset gives you.
Interesting! Makes sense though! Thanks for letting us know
The issue I see is the histogram values are near 10X the offset value. ZWO may be doing things different, but it looks like be a software bug. I can set my offset to 18 and have zero dark pixels but then the histogram Mean and Median values are near 180. For now, I am leaving it at 50 since the histogram Min value 323 (2x).@@davidkennedy3050
very cool. thank you. so mentioned you dont take darks anymore. what else do you or dont you take take?
Merry Christmas Cuiv!
Back in the long, long ago there was an article from Dr. Craig Stark (original author of PHD Guiding) that described the process for CCD cameras. When I got into CMOS cameras I read Dr. Q's article (QHYCCD) that described the same process you go over here. I basically read his article and followed the same process you highlight here. It does help to optimize your dynamic range which helps minimize frustration in imaging from Bortle 9 zones like I am in near Dallas, Texas, USA. One of these days I need to take my daughter to Tokyo so she can meet her Japanese relatives.
Good to know Dr Q describes the same method! And yes you need to bring your daughter to Toyko! ;)
Hey Cuiv! Thanks for these videos! I'm still a little confused though... Does all of this make any sense if absolutely 0 pixel of your lights frames has a 0 value? Would it still help for stretching and all?
Cuiv! I hope your well. I’ve been watching your videos for over 4 years and still one of my favorite channels. Happy new year!
thank you for this - how do I check the offset while using everything in the ZWO Eco System ? ASI Air , ASI 294MM Pro, etc.
Apparently not possible in the ASIAir, but ZWO sets a good offset value in the first place so you should be fine
@CuivTheLazyGeek Thanks for all your insights, I appreciate them all as an Astro noob. I don't know how you do it? I mean keeping your wife😃 I lost mine a few years back in another rabbit hole called Euro Rack😂 At least now the only one I can lose in the black rabbit hole is myself😅 Merry Christmas and Happy New Year🎄🌌🌠🥂
Ok I laughed far too much at your comment :) Merry Christmas!
Very helpful. A project for one day this week. Seasons greeting to you and your family.
At last!!! Someone who explained it so good!! Thank you Cuiv!
I am not involved with astrocams but are you sure that an additional offset of "only 32" is unimportant? I thougt you have to handle these numbers on a logarithmic scale - so 32 = 2 powered by 5 that means you have lost 5 bits!
Maybe I am wrong ??
Maybe I found my error - you have to compare 65536 to 65536-32 and this is much less than 1 bit .... still a little bit confused 😕 good night
Finally someone answers my question on Offset. I have seen it on NINA, in the sequencer, and never knew where to set it, or what to set it too. I have the OGMA AP26CC camera now, which I think is the same as the Topek ?? that you have, with the Sony 571 chip. I love the camera, but this will really help me get the maximum performance from it. Thank you very much for making this video. I really love NINA as well, but wish I knew how to use it better. Thanks for this, and many of your other videos...all very helpful. Mark
Glad this is helpful Mark!
Merry Christmas! Yes, a lot of people afraid to use a high offset, somehow the loss of dynamic range scares people I guess, but seeing images from people their loss of DR is more contributed to incorrect processing and I'm guilty of that too. I would say on average; without careful image editing; people ruin their DR in their image by cutting as much as many thousands of ADU steps, compared to a few hundreds that a higher offset would do. The loss of DR with the offset just irrelevant and minuscule, compared to wrong image editing habits. I just follow how ZWO set it in Asiair, (offset 75 for zwo cameras) and seeing how that's like almost halfway up on the offset scale, I imitate it to do similar with my non-zwo cameras and I am perfectly fine losing a few hundred or even a 1000 DR steps due to high offset. Otherwise Pixinsight will report me that it had to do a "huge pedestal" correction when processing and that lets me know that I did use the wrong offset.
I love the work you do and your contribution to AP. I have a RASA11 and I am worried about doing a "tilt correction". Please consider a review of this factor and how to do the procedure.
Thanks Steve! Tilt is one of those things I have never had success with - and imo unless someone is using full frame and a Tak, it may not be worth the effort... Right now I'm definitely not qualified to make such a video unfortunately!
So many light bulb moments in this video. Thank you so much.
Now how do you remove clouds from your imaging 😁
TO remove clouds, you can join my Patreon, guaranteed to work!(not) :D
Thanks for the video! Appreciate the insight. Wanted to know if the offset process you described is target independent? In other words, once this has been set, one does not need to change it ever again?
Yep once it's set high enough it's pretty much target independent! Set once and forget (unless you change gain)!
Thanks Cuiv, finally a simple explanation along with a demonstration of contrast setting!
I measure the sky brightness around my target with Sharpcaps smart histogram brain function. Assuming you have previously performed a sensor analysis ( only need to perform this once) Sharpcap with work out your offset, optimal gain, sub length, exposure etc. I mean how easy was that?
Super cool!
Very helpful! Thanks Cuiv, I’ll admit I did not fully understand this before.
Glad it's helpful!
Here’s your comment you cheeky monkey! I always learn so much from you, and I truly appreciate your hard work.
Haha thank you!
Thanks, Cuiv now I know how to check the offset. My ZWO ASI2600MC Duo default offset is also 50 but this gives the histogram Mean and Median values near 500. For any offset the Mean and Median histogram values near 10X the offset.
UPDATE Looking at the fits header, NINA is added 50 as the offset not the 500 being added my ZWO.
Yep seems this is how ZWO have defined their offset!
Another great video
Merry Christmas ‘tis like a present under the astrophotography tree! Now that I’m starting to use MeleQ in addition, this is quite relevant. Re. ASIAIR, I heard ZWO ASIAIR set an offset of 45 or so to the 2600 at 101 gain…but I need to look again on Cloudy Night! I will read through the comments here too.🎉❤
Yep it seems the ASIAir hides the offset and sets it to a suitably high value to make it easier to the end user! And their offset units are different from what I heard