383L+ Flat Problem or camera problem?

[MarsLander]

Hi all,

last August I decided to buy a CCD Atik 383L + Mono, but due to bad weather and also due to lack of time I have not had the opportunity to do many tests. finally this weekend I was able to do something.
That attachment is a flat luminance.
I tried to verify if the shadow in the corner is caused by the OAG EFW2 but is not caused by this. At the end I also did a test with another CCD (QHY8L) but this defect does not appear even if the sensor has a larger size.
I also checked the firmware version installed on the 383L + has resulted 3.33.
So I tried to install the firmware version suggested by the wizard and has been installed with version 3.27
Does anyone have any idea about this?

Regards
Oscar

[GH-ATIK]

Oscar ,
It seems like the shutter , make a test with 1 or more seconds ( I think, you have a very short capturetime )

Gerhard

[MarsLander]

thanks for replay.
The time for luminance flat si about 1.05 sec.
The time is not possible to increase for flat because the light for flat is very low (minimum adjustment)
How can i solve this?

Can i reinstall the firmware 3.33 ?

Oscar

[GH-ATIK]

If light ist too bright : put some sheets of paper in front of the lens.
If light ist too low : make skyflats or use lightfoil

Gerhard

[dkordella]

Is there an ideal time for flat exposures? I created a set of flats but they do not seem to be doing much to correct my vignetting. I have a 383l+ I'm using the Atik EFW2 filter wheel with 1.25" Astrodon series 2 RGB filters. My flat exposures were all 1.0 seconds, and they *seemed* to look correct (I had an ADU of ~45,000) but in my calibrated images the vignetting is still pretty bad.

Any thoughts? I really don't want to look at upping the size of my filters...

[sazam91]

I think if you use 1.25" filters with the filterwheel, it causes vignetting. I originally ordered the 1.25" filters when I ordered the camera kit and realized when installing them that they were the wrong size. I called OPT and returned the 1.25" and bought the 36mm filter set since they are the right size for EFW2 model. They also confirmed that the 1.25" set of filters are known to cause vignetting. So that could be your issue.

Also, I believe an ADU between 32,000 to 37,000 is what is used by most but I've haven't taken any flats yet so take that with a grain of salt. 
You can try searching on Google and see what ADU values other 383 owners are using.
The capturing software Sequence Generator Pro has a tool that automatically finds the correct exposure time for the intended ADU value. You can incorporate that into your capture profile.

-Sal

[sazam91]

I should add that if you use 1.25" filter set with a fast scope, then you will see vignetting. I searched around the web for ideal ADU value and I am seeing mixed results raging from 25,000 to 35,000 and even 40,000.

Links:
http://www.atik-cameras.com/forum/index.php?topic=129.0
http://www.atik-cameras.com/forum/index.php?topic=352.0
http://www.cloudynights.com/topic/dusk-sky-flats-with-atik-383l?reply=374815349538621953
http://starizona.com/acb/ccd/advimcal.aspx

-Sal

[NickK]

For lights, I prefer to use a 3 second exposure to about 2/3 depth to ensure good SNR. To get 3 seconds that I'll use a white t-shirt (never worn or washed) and a Aurora panel. I'd take flats for each filter - regardless of par focal statements by manufacturers (I'm using Baader filters), each filter can have dust during the course of a long run.

I went straight to 2" filters for maximum compatibility for scope/cameras.