Zero or insignificant signal detected (empty image?)

[Steve Selwood]

I have recently purchased an ASI 1600MM-Pro and spent a few nights acquiring some data to process as my dark nights have vanished until late July. I thought all was going well and my light frames were looking good.

I proceeded to take dark frames, flat frames and dark flats (flats darks?) Things started going downhill :-(

When trying to integrate either the dark frames or the flat dark frames I get the following error message "Zero or insignificant signal detected (empty image?)" I have tried to see what is going wrong to no avail. I have followed the settings at 6.1 in https://pixinsight.com/forum/index.php?threads/for-beginners-guide-to-pis-imagecalibration.11547/. Exactly the same error message. Various other threads and Youtube videos following the respective authors setting, exactly the same error. I only get the error with dark frames or flat dark frames. I am able to integrate the light and flat frames with no problems. Thinking I may have inadvertently changed something in PI I tried integrating dark frames from my Nikon D750, no problem all worked perfectly. I am using PI V 1.8.8-5 on Windows 10, I have tried on two different computers but still the same error.

I am now officially stuck and frustrated. I figure I must be doing something wrong but after two days of fiddling taking new dark frames and trying all sorts of permutations I have no ideas left.

In case I am doing something oddly wrong in my dark frame acquisition I have posted the files in dropbox https://www.dropbox.com/sh/y9bpsx6rhje2w4v/AAB5lJxrD8IpcDpdaT0hRU3ba?dl=0

I'd be really grateful if someone could point out to me what stupid mistake I a making, thank you.

 

[bulrichl]

Hi Steve,

the 3 dark frames (exposure time: 120 s) contain the intensity value of 16 ADU for 99.86 % of the pixels. This is unexpected. The Panasonic MN 34230 has a 12-bit A/D converter, and the camera driver scales the data to 16 bit (i.e.: multiplies by factor 16). Inspecting the FITS header reveals that the settings were: gain 10, offset 0. An offset value of 0 is certainly not the default setting. I guess that the zero offset setting is causing the weird result. The light frames that were captured with this setting are not usable.

There are numerous threads in different forums about suitable combinations of gain and offset. I cite Jon Rista who uses this camera for years:

"That said, most ASI1600 imagers are using Gain 0 and/or Gain 76 (Offset 15) for LRGB, Gain 139 (unity) or Gain 200 (Offset 30-50) for NB, and are using exposures ranging from 30s to a few minutes for LRGB, and 90-300s or so for NB."

Please also take a look at chapter 5 of my guide for other important conditions for the acquisition of the calibration frames.

Bernd

 

[Steve Selwood]

Hi Steve,

the 3 dark frames (exposure time: 120 s) contain the intensity value of 16 ADU for 99.86 % of the pixels. This is unexpected. The Panasonic MN 34230 has a 12-bit A/D converter, and the camera driver scales the data to 16 bit (i.e.: multiplies by factor 16). Inspecting the FITS header reveals that the settings were: gain 10, offset 0. An offset value of 0 is certainly not the default setting. I guess that the zero offset setting is causing the weird result. The light frames that were captured with this setting are not usable.

There are numerous threads in different forums about suitable combinations of gain and offset. I cite Jon Rista who uses this camera for years:

"That said, most ASI1600 imagers are using Gain 0 and/or Gain 76 (Offset 15) for LRGB, Gain 139 (unity) or Gain 200 (Offset 30-50) for NB, and are using exposures ranging from 30s to a few minutes for LRGB, and 90-300s or so for NB."

Please also take a look at chapter 5 of my guide for other important conditions for the acquisition of the calibration frames.

Bernd

 

[Steve Selwood]

Hi Bernd,

Thanks you very much for that information.

I have just taken some new darks with a Gain of 139 and Offset of 40. Firstly they look so much better than the previous darks. Secondly I can integrate them in PI. It is certainly a different world than my DSLR where I only had to concern myself with ISO.

The light frames with the gain of 10 and offset of 0 are better than I was getting with my DSLR, especially being locked down about 30m from a street lamp. They were taken with an Ha filter. Sadly I won't be able to apply any calibration frames to them but at least I have an early indication of what I may be able to achieve when dark and hopefully clear skies return in late July.

Lastly than you for producing the guide, I think the only thing I was doing drastically wrong with all of my images was the gain and offset issue.

Steve