Arun H:
Dale Penkala:
If you search “flat issues 294” there is many threads over on CN (cloudy nights) that address this problem.
The issues with the 294 sensor seem to relate to how it handles timing for short exposures. Timing for very short exposures is handled by on chip circuitry which heats the sensor and messes the temperature. The reason to force exposures of 4 seconds or more is to avoid this, and also to ensure that the exposure is long enough that timing errors introduced by driver controlled timing for longer exposures does not become a factor.
This is very likely what I saw all those years ago. Good to know there's a way to work around it. 🙂
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andrea tasselli:
Never had an issue with that and I don't put any stock in the effect of temperature on exposures less than a second.
I would look up John Upton's work. Pretty quantitative.
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Bill Long - Dark Matters Astrophotography:
andrea tasselli:
Dale Penkala:
If you do the research on the 294 & 071 you will see that 3-5 second flats are recommended. Once I did that it fixed all the problems I ever had and followed thru with my 2600.
Recommended by whom? Not by me. I have the ASI294MC, HC533C, AA26C (IMX571) and ASI294MM and I can't find a single reason for this assumption.
Couldn't ever get the 294C to produce images without a massive red blotchy mess in the background. This was years ago though so maybe those problems are over these days.
Yes I think a while back this was an issue but was figured out by many. I know that I stated CN but here is a good example about what I’m talking about here.
https://forums.sharpcap.co.uk/viewtopic.php?t=2999
This was just a quick google search but I’m sure I could dig a bit more and find that CN thread that I read and followed.
But, we need to get back to the OP issues.
Dale
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I believe he's going to shoot longer flats as a test. That and getting an image uploaded with the example of what he's seeing.
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Bill Long - Dark Matters Astrophotography:
I believe he's going to shoot longer flats as a test. That and getting an image uploaded with the example of what he's seeing.
Both would be helpful Bill
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Hello All,
My L flats at 3910 mm never seem to apply properly in WBPP; or at least not as well as the RGB flats. SHO always seem to work well. All else being the same.
Values are consistent, calibration method in WBPP is consistent (with the other filters and in general when ever I take flats for my other rigs etc. In other words, I'm pretty sure that I'm not making any glaring errors). I use bias and darks all at the same gain, offset and temperature (and sub time in the case of darks).
I have tried several config differences in WBPP as well with no obvious differences.
Furthermore, the other night, in order to eliminate possible filter wheel positioning errors, and/or any chance of the flats being "stale"; I immediately took new flats right after about four hours of L data collection and they still presented the same problem. Some motes simply do not get cleared and a general blotchiness (is that a word?!) exists. I can cheat a bit with Clone Stamp but would rather address it properly. Oh, and sky or LED flats present the same issue.
I haven't disassembled yet to look but is it possible that some humidity based "slime" could have built up on the filter? But if so, why not the others?
Any ideas would be appreciated!
Since getting back into astrophotography this year, after having been out of it for several years...I have been surprised by how many threads on various fourms I've encountered where people have noted calibration issues with WBPP.
I am just curious...have you tried to create your own master flat, without using WBPP? WBPP is somewhat of a black box at times, and I now often wonder if it is doing something incorrectly with the way it produces masters, particularly master flats. If you manually create your master flat, I wonder if it would help resolve the issue.
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I wouldn't ever use WBPP so it won't apply to me. But, yes, in general is best avoided when investigating things not working. Keep it as simple as possible but not simpler.
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Light pollution really wreaks havoc on how lum flats correct things. I never figured it out. I finally went remote to solve the problem. But even then, when the moon is out, I might get lum subs where I can correct the gradient, but then the flats no longer work as well--especially the luminance flats. One thing that did help is that I went from taking 20 flats to 50. So I would recommend trying more flat subs, or as others have suggested, lengthening the duration of the flats.
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andrea tasselli:
Dale Penkala:
If you do the research on the 294 & 071 you will see that 3-5 second flats are recommended. Once I did that it fixed all the problems I ever had and followed thru with my 2600.
Recommended by whom? Not by me. I have the ASI294MC, HC533C, AA26C (IMX571) and ASI294MM and I can't find a single reason for this assumption.
Short flats on the 294 are poor in my experience with both the MC and the MM. The banding becomes problematic and degrades the flats. 3-5s, in my case, *did* dramatically improve the quality of those calibration frames for this sensor. As was also the case with the 183.
I have used a few 2600 cameras and have not had issues with very short flats in those cases. That sensor is very clean.
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Timothy Martin:
Light pollution really wreaks havoc on how lum flats correct things. I never figured it out. I finally went remote to solve the problem. But even then, when the moon is out, I might get lum subs where I can correct the gradient, but then the flats no longer work as well--especially the luminance flats. One thing that did help is that I went from taking 20 flats to 50. So I would recommend trying more flat subs, or as others have suggested, lengthening the duration of the flats.
Keep in mind that an LP gradient is not, and never has been, something that flats will or could ever correct.
Flats will only correct the intrinsic field shape and structure as dictated by your scope and image train. Light pollution is an external pollutant signal, and flats have never been capable of correcting that. Hence the reason why we have gradient correction/extraction processes in our pre-processing tools (GraXpert or the new GradientCorrection tool in PI).
If you are hoping that flats will or could correct LP gradients, then know that its never been the domain of flats. Even at a dark site, you can still have gradients. I imaged a lot at a dark site for several years, and often ran into moderately to very high Airglow, which can introduce a notable greenish or brownish tint and often gradients into the images. Additionally, if I tracked on any particular target for too long, I would sometimes run into the upper reaches of the Denver LP bubble, which was on the western horizon. Gradients and their correction are often a real-world fact of life with astrophotography, and have never been the domain of flats. Flats should try to properly model the optical space, but nothing more.
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James Peirce:
andrea tasselli:
Dale Penkala:
If you do the research on the 294 & 071 you will see that 3-5 second flats are recommended. Once I did that it fixed all the problems I ever had and followed thru with my 2600.
Recommended by whom? Not by me. I have the ASI294MC, HC533C, AA26C (IMX571) and ASI294MM and I can't find a single reason for this assumption.
Short flats on the 294 are poor in my experience with both the MC and the MM. The banding becomes problematic and degrades the flats. 3-5s, in my case, *did* dramatically improve the quality of those calibration frames for this sensor. As was also the case with the 183.
I have used a few 2600 cameras and have not had issues with very short flats in those cases. That sensor is very clean.
The length shouldn't really be a factor, on any camera, unless there is some kind of signal scanning issue...
Flats are about signal level. If you are getting 40-60% signal in all the pixels, then your flats should be WELL above the dark signal and DFPN level. If you are still getting banding, that sounds like a readout problem, which might be electrical, interference, or maybe poor cabling?
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Jon Rista:
Flats will only correct the intrinsic field shape and structure as dictated by your scope and image train. Light pollution is an external pollutant signal, and flats have never been capable of correcting that. Hence the reason why we have gradient correction/extraction processes in our pre-processing tools (GraXpert or the new GradientCorrection tool in PI).
I don't think the more experienced of us have any expectation that flats will correct light pollution gradients.
The issue comes down to the fact (I think) that because of so much light interference, flats can never mimic correctly enough the pathway of light coming through the scope and the problem gets worse with worsening light pollution. Things like shielding, flocking etc., help, but my experience has been that their efficacy becomes more and more critical the worse the light pollution is. The artifacts I have experienced with luminance correction from Bortle 6 have nothing to do with light pollution gradients and everything to do with things like reflections, not blocking stray light adequately etc. etc. Under near identical conditions, narrowband flats and even RGB flats correct perfectly. As do luminance flats at Bortle 4 sites.
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Jon Rista:
James Peirce:
andrea tasselli:
Dale Penkala:
If you do the research on the 294 & 071 you will see that 3-5 second flats are recommended. Once I did that it fixed all the problems I ever had and followed thru with my 2600.
Recommended by whom? Not by me. I have the ASI294MC, HC533C, AA26C (IMX571) and ASI294MM and I can't find a single reason for this assumption.
Short flats on the 294 are poor in my experience with both the MC and the MM. The banding becomes problematic and degrades the flats. 3-5s, in my case, *did* dramatically improve the quality of those calibration frames for this sensor. As was also the case with the 183.
I have used a few 2600 cameras and have not had issues with very short flats in those cases. That sensor is very clean.
The length shouldn't really be a factor, on any camera, unless there is some kind of signal scanning issue...
Flats are about signal level. If you are getting 40-60% signal in all the pixels, then your flats should be WELL above the dark signal and DFPN level. If you are still getting banding, that sounds like a readout problem, which might be electrical, interference, or maybe poor cabling?
There’s always opportunity for cabling issues, but it would be odd for that issue to be something I have experienced with these specific cameras and not others. And this is also a well-documented issue with these specific cameras. The banding can be come increasingly more erratic relative to what calibration frames can normalize, resulting in sub-optimal correction. And it does make sense for inconsistent sensor issues to create an issue in a case like this as we aren’t just addressing noise.
In any case, consistent with others’ experience that has been shared many times, longer exposures on these sensors *did* correct the issues I was dealing with.
On my 294MM I have also noticed that the banding doesn’t calibrate well when exposures are short relative to reasonable saturation of the sensor, and performance is dramatically improved with good exposures, including banding calibrating soundly with darks.
I use high quality cables and have taken great care in managing this issues while they were issues I was dealing with, hence I happily stand behind the recommendation that ~3-5s flats be used with these cameras.
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Arun H:
3.81
messierman3000#29 minutes ago· 44 views
What is an L flat?
Little Flat, Lacerta Flat, Large Flat, Live Flat, Luminance Flat, Lizard Flat????
Was really hoping it was a Lizard Flat. On second thoughts, may be not. That's probably a lizard that's been run over by a bus.
poor lizard, was just trying to get some sun   |
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Arun H:
Jon Rista:
Flats will only correct the intrinsic field shape and structure as dictated by your scope and image train. Light pollution is an external pollutant signal, and flats have never been capable of correcting that. Hence the reason why we have gradient correction/extraction processes in our pre-processing tools (GraXpert or the new GradientCorrection tool in PI).
I don't think the more experienced of us have any expectation that flats will correct light pollution gradients.
I was responding directly to someone who seemed to think that flat correction could fix gradient issues. At least the comments in the post I responded to indicated that flats would pick up a lunar gradient (in which case, I would strongly question how the flats were being crafted...) among other things. Flats should model the optics, not the sky.
I do think that how you create your flats can matter. A flat panel at the aperture isn't necessarily going to project light the same way as, say, a clear blue sky (my preferred light source, if I can use it.) A clear blue sky is effectively at the same distance as a light polluted sky, and should result in similar propagation of light through the optical train. Otherwise, I wholly agree with you that you should be eliminating stray reflections, baffling to block unwanted light where it doesn't belong, etc. to optimize your light path and minimize issues there.
I think a key issue with flats is often that the light source is at the aperture. Further, if that light source isn't ENTIRELY diffuse, if it has any structure or pattern of any kind (i.e. rows of LEDs that are still visible behind a diffuser) then there is no telling how different the wavefront may be from a sky flat of any kind, or light during the night, an issue that many non-expert imagers may not recognize at first.
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James Peirce:
Jon Rista:
James Peirce:
andrea tasselli:
Dale Penkala:
If you do the research on the 294 & 071 you will see that 3-5 second flats are recommended. Once I did that it fixed all the problems I ever had and followed thru with my 2600.
Recommended by whom? Not by me. I have the ASI294MC, HC533C, AA26C (IMX571) and ASI294MM and I can't find a single reason for this assumption.
Short flats on the 294 are poor in my experience with both the MC and the MM. The banding becomes problematic and degrades the flats. 3-5s, in my case, *did* dramatically improve the quality of those calibration frames for this sensor. As was also the case with the 183.
I have used a few 2600 cameras and have not had issues with very short flats in those cases. That sensor is very clean.
The length shouldn't really be a factor, on any camera, unless there is some kind of signal scanning issue...
Flats are about signal level. If you are getting 40-60% signal in all the pixels, then your flats should be WELL above the dark signal and DFPN level. If you are still getting banding, that sounds like a readout problem, which might be electrical, interference, or maybe poor cabling?
There’s always opportunity for cabling issues, but it would be odd for that issue to be something I have experienced with these specific cameras and not others. And this is also a well-documented issue with these specific cameras. The banding can be come increasingly more erratic relative to what calibration frames can normalize, resulting in sub-optimal correction. And it does make sense for inconsistent sensor issues to create an issue in a case like this as we aren’t just addressing noise.
In any case, consistent with others’ experience that has been shared many times, longer exposures on these sensors *did* correct the issues I was dealing with.
On my 294MM I have also noticed that the banding doesn’t calibrate well when exposures are short relative to reasonable saturation of the sensor, and performance is dramatically improved with good exposures, including banding calibrating soundly with darks.
I use high quality cables and have taken great care in managing this issues while they were issues I was dealing with, hence I happily stand behind the recommendation that ~3-5s flats be used with these cameras.
I wonder if the camera uses a different kind of readout mode for shorter exposures. Something more akin to a video-style readout, which may lead to the banding. It is the 294...that sensor seems to have a multitude of little issues, kind of like the Panasonic M, which also had problematic readout issues at certain exposure settings.
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Jon Rista:
It is the 294...that sensor seems to have a multitude of little issues
What I will say about that sensor is that it would not be my first, second, or third choice for really deep images. There was always a little bit of residual amp glow no matter how carefully I calibrated it, which became problematic with images where there wasn't sufficient sky background or nebulosity to overwhelm the lack of perfect correction.
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James Peirce:
Short flats on the 294 are poor in my experience with both the MC and the MM. The banding becomes problematic and degrades the flats. 3-5s, in my case, *did* dramatically improve the quality of those calibration frames for this sensor. As was also the case with the 183.
I have used a few 2600 cameras and have not had issues with very short flats in those cases. That sensor is very clean.
Your experience isn't anything like mine but rest assured that my flats calibrate just fine as far as they are concerned.
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andrea tasselli:
James Peirce:
Short flats on the 294 are poor in my experience with both the MC and the MM. The banding becomes problematic and degrades the flats. 3-5s, in my case, *did* dramatically improve the quality of those calibration frames for this sensor. As was also the case with the 183.
I have used a few 2600 cameras and have not had issues with very short flats in those cases. That sensor is very clean.
Your experience isn't anything like mine but rest assured that my flats calibrate just fine as far as they are concerned.
We may just have different definitions of “fine.” I’ve noticed that happens a lot in this hobby.
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Arun H:
Jon Rista:
It is the 294...that sensor seems to have a multitude of little issues
What I will say about that sensor is that it would not be my first, second, or third choice for really deep images. There was always a little bit of residual amp glow no matter how carefully I calibrated it, which became problematic with images where there wasn't sufficient sky background or nebulosity to overwhelm the lack of perfect correction.
Given the sheer volume of issue posts/threads with the 294s, I wouldn't choose one for any reason. A thread many years ago on CN, ended up revealing that the way Sony sells those sensors, they are pre-packaged on a little PCB. Apparently the way that is done, they cannot be cooled effectively or consistently, which is a key part of why they are so problematic. Its just not a sensor package that is really viable for the context of AP.
Its too bad its become such a popular sensor... It seems quite a lot of imagers have one these days, and a lot of them seem to have issues with it. Wonder if there is a way to get the word out that there are significantly better options for more trouble-free imaging... O_o
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James Peirce:
We may just have different definitions of “fine.” I’ve noticed that happens a lot in this hobby.
Indeed. I'd stick with mine.
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Jon Rista:
Given the sheer volume of issue posts/threads with the 294s, I wouldn't choose one for any reason. A thread many years ago on CN, ended up revealing that the way Sony sells those sensors, they are pre-packaged on a little PCB. Apparently the way that is done, they cannot be cooled effectively or consistently, which is a key part of why they are so problematic. Its just not a sensor package that is really viable for the context of AP.
Its too bad its become such a popular sensor... It seems quite a lot of imagers have one these days, and a lot of them seem to have issues with it. Wonder if there is a way to get the word out that there are significantly better options for more trouble-free imaging... O_o
You talk a lot about it but haven't got one. How weird.
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Jon Rista:
James Peirce:
Jon Rista:
James Peirce:
andrea tasselli:
Dale Penkala:
If you do the research on the 294 & 071 you will see that 3-5 second flats are recommended. Once I did that it fixed all the problems I ever had and followed thru with my 2600.
Recommended by whom? Not by me. I have the ASI294MC, HC533C, AA26C (IMX571) and ASI294MM and I can't find a single reason for this assumption.
Short flats on the 294 are poor in my experience with both the MC and the MM. The banding becomes problematic and degrades the flats. 3-5s, in my case, *did* dramatically improve the quality of those calibration frames for this sensor. As was also the case with the 183.
I have used a few 2600 cameras and have not had issues with very short flats in those cases. That sensor is very clean.
The length shouldn't really be a factor, on any camera, unless there is some kind of signal scanning issue...
Flats are about signal level. If you are getting 40-60% signal in all the pixels, then your flats should be WELL above the dark signal and DFPN level. If you are still getting banding, that sounds like a readout problem, which might be electrical, interference, or maybe poor cabling?
There’s always opportunity for cabling issues, but it would be odd for that issue to be something I have experienced with these specific cameras and not others. And this is also a well-documented issue with these specific cameras. The banding can be come increasingly more erratic relative to what calibration frames can normalize, resulting in sub-optimal correction. And it does make sense for inconsistent sensor issues to create an issue in a case like this as we aren’t just addressing noise.
In any case, consistent with others’ experience that has been shared many times, longer exposures on these sensors *did* correct the issues I was dealing with.
On my 294MM I have also noticed that the banding doesn’t calibrate well when exposures are short relative to reasonable saturation of the sensor, and performance is dramatically improved with good exposures, including banding calibrating soundly with darks.
I use high quality cables and have taken great care in managing this issues while they were issues I was dealing with, hence I happily stand behind the recommendation that ~3-5s flats be used with these cameras.
I wonder if the camera uses a different kind of readout mode for shorter exposures. Something more akin to a video-style readout, which may lead to the banding. It is the 294...that sensor seems to have a multitude of little issues, kind of like the Panasonic M, which also had problematic readout issues at certain exposure settings.
Maybe… it’s an interesting thought. I couldn’t suggest a better theory. Unless maybe some aspect of the banding behavior becomes a lot more stable under longer exposures and hence calibrates more reliably for some other reason.
I did eventually get both cameras (MC now sold, MM I ponder parting with) performing reasonably. But I had to jump through hoops to get there. I don’t know if it’s a sensor issue or what, but they’re not cameras I’m fond of recommending. By contrast my experience with the 2600 is always everything calibrating so splendidly. I also always had smooth calibration with the 1600MM, and it wasn’t the cleanest sensor.
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andrea tasselli:
Jon Rista:
Given the sheer volume of issue posts/threads with the 294s, I wouldn't choose one for any reason. A thread many years ago on CN, ended up revealing that the way Sony sells those sensors, they are pre-packaged on a little PCB. Apparently the way that is done, they cannot be cooled effectively or consistently, which is a key part of why they are so problematic. Its just not a sensor package that is really viable for the context of AP.
Its too bad its become such a popular sensor... It seems quite a lot of imagers have one these days, and a lot of them seem to have issues with it. Wonder if there is a way to get the word out that there are significantly better options for more trouble-free imaging... O_o
You talk a lot about it but haven't got one. How weird.
Of course I don't!  I've processed plenty of data from them, though, going back years and years. I've had two people share their 294 data with me recently asking for help. I don't care for it, the data is always dirty and difficult. I don't want one, and I try to warn people away from that sensor whenever I get the chance. This hobby is usually more than challenging enough, without adding a problematic sensor that can't be cooled well into the mix.
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11.02
11.91
15.85
8.59
7.72
11.04
2.11
4.02
