Background artifact issue

ASI's Range of Specialised CMOS camera's

Moderator: Sam

AhBok
Posts: 7
Joined: Sat Mar 19, 2016 9:01 pm

Re: Background artifact issue

Post by AhBok » Fri Jun 01, 2018 7:44 pm

Sam—Please add me to the list of users with this problem. I cannot use anything longer than 60 seconds and must use at least 199 gain in order to minimize the effect. I, too, use lights, darks, flats, and dark flats. I get this stacking in both DSS and APP. I really want to image this summer at a dark site using a gain setting with a larger DR. Please advise what we ASI294 are to do.

Randy Roy

User avatar
Support@ZWO
Posts: 852
Joined: Mon Apr 24, 2017 10:08 am

Re: Background artifact issue

Post by Support@ZWO » Mon Jun 04, 2018 1:18 am

Hi, Andy was the first user report this. I read his post, looks he use 2min exposure to reduce the artifact. Another guy use Sony A7 looks have same issue, he wrote a post too, I think he find some way in processing to reduce the issue.
https://www.cloudynights.com/topic/5762 ... n-swathes/
Location:lon=120.6 lat=31.3
Suzhou China

jmtanous
Posts: 10
Joined: Fri Jan 05, 2018 10:10 pm

Re: Background artifact issue

Post by jmtanous » Wed Jun 06, 2018 5:46 pm

Sean.Wang wrote:Hi, Andy was the first user report this. I read his post, looks he use 2min exposure to reduce the artifact. Another guy use Sony A7 looks have same issue, he wrote a post too, I think he find some way in processing to reduce the issue.
https://www.cloudynights.com/topic/5762 ... n-swathes/
Hi,

According to Mark, the guy who reported a similar issue with the Sony A7, he hasn't found a solution to this issue with the Sony A7. Probably the issue is not related at all but it looks similar to the one reported here.

https://www.cloudynights.com/topic/5960 ... ?p=8623769

What Mark suggested is that the Sony A7 issue might be related to some onboard processing of the flats.

I will create a couple of master flats created with exposure times and I will try to calibrate them between each other. I will post my results, this might give us some ideas if the issue is similar to the one reported on Sony A7.

Cheers,

Jose

User avatar
Support@ZWO
Posts: 852
Joined: Mon Apr 24, 2017 10:08 am

Re: Background artifact issue

Post by Support@ZWO » Thu Jun 07, 2018 2:44 am

Thank you, I think issue of A7 is quite like 294, the phenomenon is nearly the same.
Location:lon=120.6 lat=31.3
Suzhou China

bulrichl
Posts: 27
Joined: Sun May 27, 2018 9:18 am
Location: La Palma (Canary Islands)

Re: Background artifact issue

Post by bulrichl » Thu Jun 07, 2018 4:42 pm

Hi Sean,

up to now there was not much help from ZWO in respect to the colored background artifact issue with the ASI294MC Pro. What I read from you was only guesswork so far.

Is ZWO even working on that problem currently? What are the findings then?

Bernd

vichman
Posts: 12
Joined: Tue Aug 01, 2017 8:26 pm

Re: Background artifact issue

Post by vichman » Fri Jun 08, 2018 6:11 am

Dear Sam,
Dear Sean,

I would also be very interested to hear about your own findings and your suggestion on how to deal with this.
So far I haven't experienced this observation with my ASI294 myself, but I would like to be prepared.

Thanks very much in advance.

Stefan
Last edited by vichman on Tue Jun 12, 2018 10:27 am, edited 2 times in total.

jmtanous
Posts: 10
Joined: Fri Jan 05, 2018 10:10 pm

Re: Background artifact issue

Post by jmtanous » Fri Jun 08, 2018 10:32 pm

Hi,

These are some master flats created with different exposures times, 1s and 5s. A flatman screen with controllable brightness was used to for the capture. The histogram of the flats had 3 humps, the green hump was ending close to 30k ADU. The red and blue humps were close to 11k ADUs. The flats were calibrated using 64 darks of the same exposure time per set. The master flats were created by integrating 64 individual flat frames per set.

I am also attaching an uncalibrated 60s light frame. I calibrated it just using the master flats and it looks like the master flat overcorrects the light frame.

Feel free to download and play with the images. They were

Calibrated 5s master flat:

https://drive.google.com/open?id=17c0Zv ... 5xJKFJGBvl

Calibrated 1s master flat:

https://drive.google.com/open?id=1uk4DW ... Y9oPretAES

Uncalibrated 60s raw light of M13

https://drive.google.com/open?id=18fEoG ... Q5S6BUPHnr

I am also attaching the histogram of an individual flat frame and an integration of 88 x 1 min exposures. The images were dithered and calibrated with 128 x 1min darks and the master 5s flat frame. The image is heavily stretched to show the uneven background.

Cheers,

Jose
Attachments
backgrous.jpg
heavily stretched fully calibrated master light
histo.jpg
Histogram of single 5s flat frame

User avatar
Support@ZWO
Posts: 852
Joined: Mon Apr 24, 2017 10:08 am

Re: Background artifact issue

Post by Support@ZWO » Sat Jun 09, 2018 3:41 pm

jmtanous wrote:Hi,

These are some master flats created with different exposures times, 1s and 5s. A flatman screen with controllable brightness was used to for the capture. The histogram of the flats had 3 humps, the green hump was ending close to 30k ADU. The red and blue humps were close to 11k ADUs. The flats were calibrated using 64 darks of the same exposure time per set. The master flats were created by integrating 64 individual flat frames per set.

I am also attaching an uncalibrated 60s light frame. I calibrated it just using the master flats and it looks like the master flat overcorrects the light frame.

Feel free to download and play with the images. They were

Calibrated 5s master flat:

https://drive.google.com/open?id=17c0Zv ... 5xJKFJGBvl

Calibrated 1s master flat:

https://drive.google.com/open?id=1uk4DW ... Y9oPretAES

Uncalibrated 60s raw light of M13

https://drive.google.com/open?id=18fEoG ... Q5S6BUPHnr

I am also attaching the histogram of an individual flat frame and an integration of 88 x 1 min exposures. The images were dithered and calibrated with 128 x 1min darks and the master 5s flat frame. The image is heavily stretched to show the uneven background.

Cheers,

Jose
Thank you so much. We will keep working on this issue. We saw a post on CN said Sony A7 have same issue. that guy use some processing trick to get rid of it.
Location:lon=120.6 lat=31.3
Suzhou China

jmtanous
Posts: 10
Joined: Fri Jan 05, 2018 10:10 pm

Re: Background artifact issue

Post by jmtanous » Mon Jun 11, 2018 10:58 pm

Thank you so much. We will keep working on this issue. We saw a post on CN said Sony A7 have same issue. that guy use some processing trick to get rid of it.
Do you want me to run any other test? The camera looks very sensitive and I am really looking forward to find a solution for this issue.

Cheers,

Jose

User avatar
Support@ZWO
Posts: 852
Joined: Mon Apr 24, 2017 10:08 am

Re: Background artifact issue

Post by Support@ZWO » Tue Jun 12, 2018 11:10 am

jmtanous wrote:
Thank you so much. We will keep working on this issue. We saw a post on CN said Sony A7 have same issue. that guy use some processing trick to get rid of it.
Do you want me to run any other test? The camera looks very sensitive and I am really looking forward to find a solution for this issue.

Cheers,

Jose
Oh, thank you! If anyone found some way maybe solve this problem, please tell us. You all very good at astro imaging, we'd like to hear your suggestions!
Location:lon=120.6 lat=31.3
Suzhou China

Post Reply