Issue with my ASI1600MM-PRO - image intensity drop

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cfosterstars
Posts: 25
Joined: Fri Sep 29, 2017 5:30 pm

Issue with my ASI1600MM-PRO - image intensity drop

Post by cfosterstars » Sat Oct 19, 2019 4:33 pm

Last night, when I brought up my rig after being covered for bad weather I had a couple of nasty surprises. First my hard drive for data is dead. My mounted fanless PC has two hard drives and the main drive is OK, but I could not get the data drive to come up. That was annoying but I worked around it. The second issue is more of a problem.

I noticed that the intensity level of my images was lower than I expected. I normally start taking short exposures and watch the counts until the background comes down as it get dark. But the counts were too low. I was able to reach temperature just fine. I could take images just fine. they were just too dim. Its like the gain was off. So I tried going back to the ASCOM driver instead of the ZWO native driver and the give the same results. I rebooted my computer and re set up with the same results. I looked down the OTA and saw no evidence of frosting and the images showed no evidence of fogging. they looked perfectly normal, just dim. I tried changing gain settings from 76 to 200 and the intensity responded but still lower counts. I moved to my heart nebula target and took 300s Ha subs and compared then to the previous session and again they looked just dim. It was late and I saw no evidence that this was dew or fogging so I just let the data collect.

After work while still daylight, I looked again down the OTA to check and I could clearly see the sensor and the optics looked fine with not fogging or dew. So I set up my flats and LED panel. I compared flats intensities with my standard setup and instead of 31000 ADU I was getting 28500 ADU with the same settings. I am at a loss here to explain this, but it is an issue. I removed the camera and opened it to check the desiccant tablet. They looked fine and so did the sensor. I microwaved my desiccant tablets and re-installed them. I saw no film or any clear moisture on the sensor while it was open. I reinstalled the camera and retook flat with no change. Still about the same lower intensity.

I simply looks like the gain setting is off and I am not getting the gain expected for the setting in the software. I have tried multiple computes, USB3 cables and both the native and ASCOM drivers with no change. I can talk to the camera, get data from the camera with out issue. The images are just like they have a lower gain setting. I verified that both drivers are set at 16bits also. The dark frames are also off from my library for this camera - also like the gain is wrong. I have no problem cooling the camera.

I have an ASI1600MM-COOL on my SCT that I can move over and test also, but I think at this point I would like some outside input on what could be the issue.

cfosterstars
Posts: 25
Joined: Fri Sep 29, 2017 5:30 pm

Re: Issue with my ASI1600MM-PRO - image intensity drop

Post by cfosterstars » Sat Oct 19, 2019 6:10 pm

I have swapped out my -PRO with my -COOL on the same OTA with the same connections and will test that tonight. It is looking like there is some sort of hardware problem with the gain on the camera.

cfosterstars
Posts: 25
Joined: Fri Sep 29, 2017 5:30 pm

Re: Issue with my ASI1600MM-PRO - image intensity drop

Post by cfosterstars » Sat Oct 19, 2019 6:10 pm

I have swapped out my -PRO with my -COOL on the same OTA with the same connections and will test that tonight. It is looking like there is some sort of hardware problem with the gain on the camera.

cfosterstars
Posts: 25
Joined: Fri Sep 29, 2017 5:30 pm

Re: Issue with my ASI1600MM-PRO - image intensity drop

Post by cfosterstars » Sun Oct 20, 2019 1:19 pm

I ran many tests with my ASI1600MM-COOL. It was placed exactly as the -PRO was installed with all other factors held constant. It looks exactly like the -PRO used to look with no issues and the imaging looks great on that camera. These tests isolate the issue to the -PRO.

Katherine.Tsai
Posts: 288
Joined: Fri Dec 07, 2018 10:24 am

Re: Issue with my ASI1600MM-PRO - image intensity drop

Post by Katherine.Tsai » Mon Oct 21, 2019 12:51 pm

Hi,
Could you upload the fit file of good and bad picutures?
So I can make a compare of them?
please make sure they use the same parameters and same OTA.

cfosterstars
Posts: 25
Joined: Fri Sep 29, 2017 5:30 pm

Re: Issue with my ASI1600MM-PRO - image intensity drop

Post by cfosterstars » Mon Oct 21, 2019 5:32 pm

Yes I can do that. They look basically the same but with significantly lower intensity. I will do that tonight

Katherine.Tsai
Posts: 288
Joined: Fri Dec 07, 2018 10:24 am

Re: Issue with my ASI1600MM-PRO - image intensity drop

Post by Katherine.Tsai » Tue Oct 22, 2019 7:34 am

OK,
Please also try to adust the offset to let the histogram show its left part.

cfosterstars
Posts: 25
Joined: Fri Sep 29, 2017 5:30 pm

Re: Issue with my ASI1600MM-PRO - image intensity drop

Post by cfosterstars » Wed Oct 23, 2019 12:11 am

The two JPEGs show the change and the degradation of the camera. This is with the EXACT same optics, exposure and temperature. gain 200 offset 40; -15C, 300s
Attachments
ASI1600MM-PRO GOOD.jpg
Image just prior to issue
ASI1600MM-PRO BAD.png.jpg
Image just after issue

cfosterstars
Posts: 25
Joined: Fri Sep 29, 2017 5:30 pm

Re: Issue with my ASI1600MM-PRO - image intensity drop

Post by cfosterstars » Thu Oct 24, 2019 6:36 pm

Any response? Does this camera have a hardware issue? How do I get it fixed?

cfosterstars
Posts: 25
Joined: Fri Sep 29, 2017 5:30 pm

Re: Issue with my ASI1600MM-PRO - image intensity drop

Post by cfosterstars » Fri Oct 25, 2019 1:27 am

OK, Its a rainy night and my rig is covered so its a good time to test the bias circuit on the camera. I cooled down to -10C with no issue. I set the gain to unity at 139. So here are the bias results from SGP. I set the exposure time to 0.001s.



Offset Average Counts (16-bits)

0 16

10 105

20 281

30 441

40 608

50 768

100 1561



I took a 300s dark frame at -10C with gain 200 and compared to my dark frame master

new dark MasterDark

704 881



This looks more like a problem with the gain and not the offset.

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