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Issues with ASI183MM for Solar Ha Imaging: Grid Artifacts

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#1 joecool1211

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Posted 06 June 2018 - 07:10 AM

Hi! 

 

I have been having some issues using the new ASI183MM for solar Ha imaging. 

 

My optical chain is:
Lunt LS80Tha -> B1800 Blocking Filter -> Televue PowerMate 2x (Optional) -> ASI183MM

 

When I first used the camera, I immediately noticed a grid pattern in FireCapture:

FC-GridPattern-Small.jpg
 
The pattern is definitely from the camera and not an issue with the Lunt (and it is definitely not because the screenshot is in JPG). And it is apparent only with Ha imaging; white light moon images with a Celestron Evolution 8 are free of the artifacts. 
 
I've tried all sorts of combinations of settings in FireCapture, but the pattern remains. Using a flat does help to some extent. 
 
The advise from ZWO is that maybe the "183 is not suitable for Ha solar imaging". The product page on their website has a new note now! 
 
However, I think there would be other 183 sensor users out there. Has anyone encountered similar issues with this or other sensors?

 

Many thanks! 

 



#2 einarin

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Posted 06 June 2018 - 07:20 AM

Apparently other cameras suffer such pattern too:

https://www.cloudyni...th-qhy5iii-178/



#3 MalVeauX

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Posted 06 June 2018 - 07:50 AM

Hrm,

 

I used a 178 sensor for a while doing HA solar, no problem. But I've seen grids like these, usually was related to the Bayer matrix and scaling in an OS due to drivers.

 

I assume you've done the whole update drivers, re-install software, try other software, use a different cable, use a different USB3 port, etc?

 

Does it look different at 1:1 scale versus scaled compressed down like this?

 

Very best,



#4 PDB

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Posted 06 June 2018 - 08:24 AM

Hi,

 

yes this also happens on ASI-178MM (mine does) cameras and I also seen some reports on ASI1600MM. Usually not seen at 1:1 (but it is there) but gets more pronounced at certain scaling ranges.

 

I can get rid of it by making flats, but if you will be using the cam for full disk that will be a challenge to make them.

 

Regards,

 

Paul



#5 joecool1211

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Posted 06 June 2018 - 08:28 AM

Hrm,

 

I used a 178 sensor for a while doing HA solar, no problem. But I've seen grids like these, usually was related to the Bayer matrix and scaling in an OS due to drivers.

 

I assume you've done the whole update drivers, re-install software, try other software, use a different cable, use a different USB3 port, etc?

 

Does it look different at 1:1 scale versus scaled compressed down like this?

 

Very best,

Yes, I've done various software stuff, different cable, USB port, etc. But I will do it again just to be sure. 

 

This is a mono camera, so it should not be an issue with a Bayer matrix. My ASI290MC color camera has different sort of artifacts due to only the red pixels picking up a signal. 

 

Well, the grid is still apparent at 1:1 scale. It seems to be a grid 15- or 16-pixels wide on each side. 

 

A raw SER file (1GB) is available below if anyone wants to have a look:

https://www.dropbox....a_pipp.ser?dl=0



#6 MalVeauX

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Posted 06 June 2018 - 08:38 AM

Recently purchased or is this a permanent purchase at this point?

 

Very best,



#7 joecool1211

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Posted 06 June 2018 - 12:43 PM

Recently purchased or is this a permanent purchase at this point?

 

Very best,

This is a very recent purchase. I've approached ZWO support to seek options (exchange, etc). 



#8 joecool1211

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Posted 06 June 2018 - 12:50 PM

Hi,

 

yes this also happens on ASI-178MM (mine does) cameras and I also seen some reports on ASI1600MM. Usually not seen at 1:1 (but it is there) but gets more pronounced at certain scaling ranges.

 

I can get rid of it by making flats, but if you will be using the cam for full disk that will be a challenge to make them.

 

Regards,

 

Paul

Okay. So this issue seems intrinsic in sensors, though the severity seems to vary between cameras and imaging conditions. 

 

Do you have advice on how to make a good flat for close ups? I point to the center of the disc and cover the objective a plastic sheet. 

 

I have noticed that changing camera temperatures results in the flat being less effective. This is a problem as I am in the tropics and the camera rapidly heats up when outside in the sun. Maybe I should cover it with aluminum foil! And perhaps a cooled version of the camera might help (the issue seemed less severe at the start of the imaging session). 



#9 PDB

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Posted 06 June 2018 - 01:24 PM

Okay. So this issue seems intrinsic in sensors, though the severity seems to vary between cameras and imaging conditions. 

 

Do you have advice on how to make a good flat for close ups? I point to the center of the disc and cover the objective a plastic sheet. 

 

I have noticed that changing camera temperatures results in the flat being less effective. This is a problem as I am in the tropics and the camera rapidly heats up when outside in the sun. Maybe I should cover it with aluminum foil! And perhaps a cooled version of the camera might help (the issue seemed less severe at the start of the imaging session). 

 

Never made the link between temp and the problem, but it might be related. The problem is not always present and it usually occurs in H-Alfa. Made some perfect planetary and white light captures with the same camera. (interference on the microlenses?) Before you get the cool version, you might try to mount, a PC CPU cooler fan on the camera. (These are fairly cheap). I also seen some mount a small pc ventilator on the side of the cams so it blows air through the ventilation slits. (However in tropics the outside air might be hot and humid ...)

 

The flats: as long as it is not full disc and you have a equally illuminated field the plastic works fine. Some unfocusing will also do the trick.

 

Rrgds,

 

Paul



#10 joecool1211

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Posted 09 June 2018 - 09:19 AM

Never made the link between temp and the problem, but it might be related. The problem is not always present and it usually occurs in H-Alfa. Made some perfect planetary and white light captures with the same camera. (interference on the microlenses?) Before you get the cool version, you might try to mount, a PC CPU cooler fan on the camera. (These are fairly cheap). I also seen some mount a small pc ventilator on the side of the cams so it blows air through the ventilation slits. (However in tropics the outside air might be hot and humid ...)

 

The flats: as long as it is not full disc and you have a equally illuminated field the plastic works fine. Some unfocusing will also do the trick.

 

Rrgds,

 

Paul

Thanks for your advice, Paul. 

 

Unfortunately, ambient temp here in the tropics is around 32 deg C. I shielded the camera with foil and it was running at around 42 deg C. 

 

I'll experiment some more and get more practice at doing flats. Also been trying to do flats of full disk, which seem to work to some extent if I don't move the scope after that. 

 

I'll then make a decision on whether or not I can live with the inconvenience! 

 

Many thanks to all for the feedback and advice! 




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