Questions regarding anomalies on flats and lights using the ASI2600MM - help appreciated

[MonsterMagnet]

Hi All.

I've recently picked up an ASI2600MM and associated filters moving on from an ASI533MC.

Tonight was the first night it's been clear enough to try it out since I set up the EFW and the ASI2600MM so I ran through some imaging (using Asiair) for H, S and O filters and everything looked fine.  I then tried the LGRB filters and I saw there were strange patterns on the right hand side of the images.  I then went to do flats for the H, S and O filters to go with the lights taken earlier and these same patterns were visible on the flats.

Could someone help me out with regards to what I am seeing here?  I never saw anything like this using the ASI533MC and it seems strange I don't see it on the lights using HSO but do see it on the lights using LRGB.

I've attached a flat and a R filter image showing the issue and a H filter image not showing the issue.  I've also added the JPEGs so they are visible in the thread.

The R light actually looked much worse on the Asiair preview although you can still see the same artifacts on the right hand side of the image just less pronounced.

Cheers.

MM

Edit: I've just stacked the H, S and O and it seems fine to my tired eyes with those flats (per filter of course).

 

 

 

Flat_2.3s_Bin1_2600MM_H_gain100_20240306-231602_0.0C_0001.fit Light_IC434_120.0s_Bin1_2600MM_R_gain101_20240303-222658_-0.3C_0001.fit Light_HIP 24727_180.0s_Bin1_2600MM_H_gain100_20240306-212257_0.1C_0001.fit

Edited March 7 by MonsterMagnet

[symmetal]

It looks suspiciously like ice forming on the sensor. Flats will show it up very well, while lights may not, or only slightly, depending on how fine the ice crystal structure is.

What temperature are you cooling to? Nowadays I just cool to 0C to avoid ice problems. The ASI2600 has low dark current compared to older cameras and the small improvement in dark noise going below 0C is not worth the hassle of having to deal with possible dew or ice on the sensor. 🙂

Alan

[MonsterMagnet]

5 hours ago, symmetal said:

It looks suspiciously like ice forming on the sensor. Flats will show it up very well, while lights may not, or only slightly, depending on how fine the ice crystal structure is.

What temperature are you cooling to? Nowadays I just cool to 0C to avoid ice problems. The ASI2600 has low dark current compared to older cameras and the small improvement in dark noise going below 0C is not worth the hassle of having to deal with possible dew or ice on the sensor. 🙂

Alan

Thanks Alan.

I cool to 0C as well.  It could be dew or ice but it seems consistent - I've had it in the same places over two different nights now.  It seems to calibrate out but it looks horrible on the flats.  I will cool the camera in a bit and take another one as there should be no dew or ice as it's been inside all night.

MM

[tomato]

I know it is a pain to remove the camera but if you suspect dew or ice, this will be readily visible on the sensor window, and it will confirm the cause of the problem.

[MonsterMagnet]

Just now, tomato said:

I know it is a pain to remove the camera but if you suspect dew or ice, this will be readily visible on the sensor window, and it will confirm the cause of the problem.

Hi.

I don't suspect ice or dew though, it's been inside for 11 hours now so I just took another flat with the S filter for the same duration as yesterday and the artifacts are the same.  Any dew or ice should be long gone after 11 hours inside one would think?

Cheers.

MM

 

[tomato]

I agree, I can’t see dew hanging around for that long. 
You can get horizontal lines on your subs if the USB limit is set too low, but the pattern on your flats looks too irregular for this. I set my limit to 40 which was the recommended figure, this seems to work.

[MonsterMagnet]

So I've stacked and processed the SHO data and it seems fine.  I only really notice these artifacts on the flats and LRGB lights.

MM

[symmetal]

If it's ice and still forming at 0C it must be fairly high humidity inside the camera. Did you still cool the camera to 0C when you took the indoor flats? A quick check to eliminate whether it's ice is to take some flats without cooling the camera. Is the camera new or second hand? If the humidity inside the camera is too high, it will still form ice when cooling indoors as the sensor should be sealed from the outside air humidity.

If it's still present when uncooled then it could be a dirty film deposit on the sensor.

Alan

[MonsterMagnet]

Just now, symmetal said:

If it's ice and still forming at 0C it must be fairly high humidity inside the camera. Did you still cool the camera to 0C when you took the indoor flats? A quick check to eliminate whether it's ice is to take some flats without cooling the camera. Is the camera new or second hand? If the humidity inside the camera is too high, it will still form ice when cooling indoors as the sensor should be sealed from the outside air humidity.

If it's still present when uncooled then it could be a dirty film deposit on the sensor.

Alan

Hi.

I did cool the camera to take the indoor flats this morning - I'll take some with no cooling later on this evening.

The camera is second hand although the previous owner is very good to the point of saying he will take it back if it's an actual issue - he has given me a number of suggestions to try (such as cooling the camera slowly).

I'll take the flats with no cooling and post again in here.

Thanks.

MM

[symmetal]

As stacking with those 'patterned' flats does seem to improve the final images, it would suggest a dirty film deposit on the sensor which the flats are 'correcting'. If it was ice it would be more randomized and using those flats would make the stacked images look worse.

Perhaps the previous owner has 'cleaned' the sensor but didn't do it carefully enough, and has left some smear stains which is what you're seeing.

Alan

[MonsterMagnet]

2 hours ago, symmetal said:

As stacking with those 'patterned' flats does seem to improve the final images, it would suggest a dirty film deposit on the sensor which the flats are 'correcting'. If it was ice it would be more randomized and using those flats would make the stacked images look worse.

Perhaps the previous owner has 'cleaned' the sensor but didn't do it carefully enough, and has left some smear stains which is what you're seeing.

Alan

Hi.

I think that may be the case, it was mentioned that he might do that.  I'll look into how to clean the camera. 

I took a flat with no cooling and see the same issue so you are probably right.

Thanks.

MM

[Stuart1971]

That’s deffo not dew or ice, but an issue on the sensor window, if it was on the sensor itself it woul be a lot more in focus and sharp…

My guess would also be some sort of film on the sensor window..

[Stuart1971]

What is odd, is the perfect straight line where it stops, here

 

[symmetal]

Assuming you're using the ZenithStar 73 scope in your signature MM, and not binning, putting the large and small circular dust spots into the Astronomy Tools Dust Calculator puts the small dust circles 1.1mm in front of the sensor and the large dust circles at 10.1mm from the sensor. The smear pattern circle structure are a similar size to the small dust spot circles.

10.1mm seems a reasonable distance for the sensor protect window at the front of the camera, while the sensor itself could quite easily be 1.1mm from the front of the sensor cover glass so I'd put my bets on you having to clean the sensor itself (or the front of  its cover glass to be more precise) rather than the camera sensor protect window. 😉 That'll mean opening up the camera, though that's fairly easy. You could change the four desiccant tablets at the same time if you wished.

Your mono camera of course won't have the colour filter that's shown (Bayer matrix) 

I've used one of these sensor cleaners on my ASI071, as I ended up with dust on it after opening the camera to change the desiccant tablets, and the cleaner worked very well. You may need to use a couple of the cleaning wands on yours to make sure as your marks are more extensive..

Edit I was assuming that was a full size image you initially posted of the flat, but it's dimensions are 50% that of full size so it's either binned 2x2 or resampled to 50% before positing, or it's a crop of the original full size image. If it's binned then the Astronomy Tools dust distances calculated need to be doubled which doesn't make much sense so I'm hoping it's a full size crop. 🙂

If the Astronomy Tools calculator wants the radius of the dust spots entered and not their diameter, (it doesn't say), then it being resampled 50% means the original distances I calculated are correct. 😁

Alan

Edited March 8 by symmetal

[MonsterMagnet]

7 hours ago, symmetal said:

Assuming you're using the ZenithStar 73 scope in your signature MM, and not binning, putting the large and small circular dust spots into the Astronomy Tools Dust Calculator puts the small dust circles 1.1mm in front of the sensor and the large dust circles at 10.1mm from the sensor. The smear pattern circle structure are a similar size to the small dust spot circles.

10.1mm seems a reasonable distance for the sensor protect window at the front of the camera, while the sensor itself could quite easily be 1.1mm from the front of the sensor cover glass so I'd put my bets on you having to clean the sensor itself (or the front of  its cover glass to be more precise) rather than the camera sensor protect window. 😉 That'll mean opening up the camera, though that's fairly easy. You could change the four desiccant tablets at the same time if you wished.

Your mono camera of course won't have the colour filter that's shown (Bayer matrix) 

I've used one of these sensor cleaners on my ASI071, as I ended up with dust on it after opening the camera to change the desiccant tablets, and the cleaner worked very well. You may need to use a couple of the cleaning wands on yours to make sure as your marks are more extensive..

Edit I was assuming that was a full size image you initially posted of the flat, but it's dimensions are 50% that of full size so it's either binned 2x2 or resampled to 50% before positing, or it's a crop of the original full size image. If it's binned then the Astronomy Tools dust distances calculated need to be doubled which doesn't make much sense so I'm hoping it's a full size crop. 🙂

If the Astronomy Tools calculator wants the radius of the dust spots entered and not their diameter, (it doesn't say), then it being resampled 50% means the original distances I calculated are correct. 😁

Alan

Thanks for all that information, I'll take a look at that kit and try and get my head around the diagram and cleaning process - I was going to take it off the EFW today and have a look.  It's a bit of a pain how the EFW has to be opened up as the camera is bolted to it.

The images should be full APS-C converted to JPEG so not sure what is going on there - I'll need to check the Asiair settings.

MM

[Stuart1971]

1 hour ago, MonsterMagnet said:

Thanks for all that information, I'll take a look at that kit and try and get my head around the diagram and cleaning process - I was going to take it off the EFW today and have a look.  It's a bit of a pain how the EFW has to be opened up as the camera is bolted to it.

The images should be full APS-C converted to JPEG so not sure what is going on there - I'll need to check the Asiair settings.

MM

Personally, if you have just bought this new of from someone, I would be sending it back, and not opening the camera up at all, it should not have been sold in this state at all…and if second hand, then you need to be having a word with the seller IMHO…

[MonsterMagnet]

38 minutes ago, Stuart1971 said:

Personally, if you have just bought this new of from someone, I would be sending it back, and not opening the camera up at all, it should not have been sold in this state at all…and if second hand, then you need to be having a word with the seller IMHO…

I bought it second hand, the seller is happy to have it returned and refunded so I don't have any issues with him and that will probably be the route to go down now and purchase a new on from FLO.

MM

[Stuart1971]

2 hours ago, MonsterMagnet said:

I bought it second hand, the seller is happy to have it returned and refunded so I don't have any issues with him and that will probably be the route to go down now and purchase a new on from FLO.

MM

Good decision..

Has he said he has opened the camera up and tried to clean the sensor, as it looks that way…?

[ONIKKINEN]

Could it be the dreaded oil leak issue the 2600 suffered a few years back? Fixed in newer production runs, but since the camera is second hand maybe this is one of the affected models.

[Stuart1971]

3 minutes ago, ONIKKINEN said:

Could it be the dreaded oil leak issue the 2600 suffered a few years back? Fixed in newer production runs, but since the camera is second hand maybe this is one of the affected models.

No, looks nothing like that issue, and how it presented itself…

[ONIKKINEN]

9 minutes ago, Stuart1971 said:

No, looks nothing like that issue, and how it presented itself…

It does look different than what most of those cases looked like, but my bet is still that something is on the sensor itself or at least close to it. The pattern looks like rows and columns of pixels, if there is some residue on the sensor itself i think it could result in shadows like this.

[Stuart1971]

1 minute ago, ONIKKINEN said:

It does look different than what most of those cases looked like, but my bet is still that something is on the sensor itself or at least close to it. The pattern looks like rows and columns of pixels, if there is some residue on the sensor itself i think it could result in shadows like this.

Yes agreed, this is what we have said to the OP…👍🏻

[MonsterMagnet]

57 minutes ago, Stuart1971 said:

Yes agreed, this is what we have said to the OP…👍🏻

 

So I was taking the camera off the EFW to reattach the tilt plate to send it back and I could see the pattern on the sensor itself (not the glass window).  I was intrigued and the seller was willing to honour the return either way so I opened the front plate and it was clearly a film on the sensor.  I used a specialist cloth to remove the film and a blower and the flats are much better now.  I think I need to do that again more carefully but given there is still a tiny bit on the right but looking at the flats and what I saw posters in this thread were correct that it was a film on the sensor.

Cheers for all the help.

MM

[symmetal]

Good to see the film was easily removeable MM. If you got the camera at a good price compared to a new one, it may be worth considering keeping it, and giving it a proper clean with the sterile cleaning sticks and fluid. Up to you of course. 😊

Alan

[Stuart1971]

27 minutes ago, MonsterMagnet said:

 

So I was taking the camera off the EFW to reattach the tilt plate to send it back and I could see the pattern on the sensor itself (not the glass window).  I was intrigued and the seller was willing to honour the return either way so I opened the front plate and it was clearly a film on the sensor.  I used a specialist cloth to remove the film and a blower and the flats are much better now.  I think I need to do that again more carefully but given there is still a tiny bit on the right but looking at the flats and what I saw posters in this thread were correct that it was a film on the sensor.

Cheers for all the help.

MM

Yes deffo much better now,

‘So the seller had obviously had it apart and tried to clean himself…not sure why anyone would do that 🤷🏼‍♂️