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ASI294MC Flats help. I'm stumped!


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2 minutes ago, The Admiral said:

Now the effects are quite different to what you are finding, but Vlaiv raised an issue with APT in his post on 26 March where he thought that APT wasn't working properly. So clutching at straws, it might be worth checking it out. Sorry if this is a red herring.

Ian

You do realize that you are referring to this same thread? :D

 

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18 minutes ago, The Admiral said:

It's not the first time I've read about issues with this camera, nothing very consistent though. In this thread a particular issue is raised.

 

Now the effects are quite different to what you are finding, but Vlaiv raised an issue with APT in his post on 26 March where he thought that APT wasn't working properly. So clutching at straws, it might be worth checking it out. Sorry if this is a red herring.

Ian

Yeah I tried doing manual flats as Vlaiv suggested but still get the same result. I have been playing about with the original stack and the band can be almost eliminated with careful stretching. 

Part of me thinks it could just be gradient related as it's less than 2 hours of OSC data from a bortle 8 zone in which I imaged between 2 streetlights. Maybe more data and less aggressive stretching will sort it out? 

 

LEO Triplet.jpg

Edited by Stuf1978
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Edit, the issue was definitely flats related..... I think 😂

Managed another couple of hours on the triplet last night and shot several variations of flats. The ones without using a white t-shirt and using the flat aid with a target of 25000 ADU got rid of the banding but there were other issues. I think it will just be a case of experimentation until I find out what works with the camera. As an aside the data is much nicer to process than that from my old 450D :)

 

LEO TRIPLET 2.jpg

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Nice triplet.

Just my tuppence worth... I've had a ZWO ASI294MC Pro for several years now. I have used APT, NINA, Voyager, Sharpcap etc. etc. I've had the banding issues and its always related to the scan or switch rate of the light source, to counter this you need long flat exposures. Hence why the sky fl;ats with t-shirt work, no scan rate for the sun :) You also need long flat exposures to counter 'features' of the CMOS sensor. 3 seconds is the minimum cleverer people than me have calculated, I just follow their recommendations after wasting loads of time trying to solve it myself with trial and error. There is loads of stuff about it on Cloudy Nights as well as here on SGL.  At least you don't seem to have the colour blotch problem!

 

 

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1 hour ago, Stuf1978 said:

The ones without using a white t-shirt and using the flat aid with a target of 25000 ADU got rid of the banding but there were other issues.

I'm just an interested by-stander on the ASI294MC pro issue that you are getting, and it would be nice to get to the root of the problem.

For information, when you say 'using a white T-shirt', was this a single layer or double layer of material? I'm asking because its appearance is to my mind like Moire fringing, which you could get if two layers of cloth are together but one is stretched a little more than the other, so that the 'thread density' (my term!) is slightly different. Possibly also, the thread count of the material might be very similar to the density of the light emitting pixels of the flat aid, so you could be getting moire fringing between the fabric and the light source. All very much complete stabs in the dark here, but you never know :wink2:. What puzzles me though, is that this is not revealed by the stretched flat. Do the flats from your original look any different from the flats taken without the T-shirt?

Care to elaborate on the 'other issues'?

Did you get around to stacking with Siril?

Your latest image looks very nice by the way, I hope that you have found a way forward.

Ian

Edit. Hmm, but then you found that stacking just the darks and lights together gave you the same result. Have you checked every sub to see if anything is visible? No overhead cables to get in the way? I've got several here and I've found it's easy to try to image through one :wink2:.

Edited by The Admiral
Further thought.
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1 hour ago, dunc said:

Nice triplet.

Just my tuppence worth... I've had a ZWO ASI294MC Pro for several years now. I have used APT, NINA, Voyager, Sharpcap etc. etc. I've had the banding issues and its always related to the scan or switch rate of the light source, to counter this you need long flat exposures. Hence why the sky fl;ats with t-shirt work, no scan rate for the sun :) You also need long flat exposures to counter 'features' of the CMOS sensor. 3 seconds is the minimum cleverer people than me have calculated, I just follow their recommendations after wasting loads of time trying to solve it myself with trial and error. There is loads of stuff about it on Cloudy Nights as well as here on SGL.  At least you don't seem to have the colour blotch problem!

 

 

Thanks, yeah I've read all the threads on cloudy nights hence aiming for flats greater than 3 seconds. I haven't tried flats with the sky yet but it is definitely something I will try. It's been a while since I read all the cloudy nights info so it's probably worth revisiting it. 

 

53 minutes ago, The Admiral said:

I'm just an interested by-stander on the ASI294MC pro issue that you are getting, and it would be nice to get to the root of the problem.

For information, when you say 'using a white T-shirt', was this a single layer or double layer of material? I'm asking because its appearance is to my mind like Moire fringing, which you could get if two layers of cloth are together but one is stretched a little more than the other, so that the 'thread density' (my term!) is slightly different. Possibly also, the thread count of the material might be very similar to the density of the light emitting pixels of the flat aid, so you could be getting moire fringing between the fabric and the light source. All very much complete stabs in the dark here, but you never know :wink2:. What puzzles me though, is that this is not revealed by the stretched flat. Do the flats from your original look any different from the flats taken without the T-shirt?

Care to elaborate on the 'other issues'?

Did you get around to stacking with Siril?

Your latest image looks very nice by the way, I hope that you have found a way forward.

Ian

Edit. Hmm, but then you found that stacking just the darks and lights together gave you the same result. Have you checked every sub to see if anything is visible? No overhead cables to get in the way? I've got several here and I've found it's easy to try to image through one :wink2:.

Double layer of a white t-shirt, I haven't tried a single layer yet but that's an interesting theory so it's probably worth trying it out. I'll probably get more time at the weekend to shoot various flats and see how it works out. I haven't scrutinised all the new flats yet but when I do I'll post up on here if I discover any issues.

The other issue with shorter flats was more pronounced vignetting so they weren't correcting properly so I still haven't got a way forward for definite. However, it's early days with the camera and you always get teething problems to iron out with new kit. I haven't had a chance to stack with Siril as of yet but will at some point and yeah I checked every light frame and nothing was apparent. Isn't astrophotography wonderful :) 

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