I have this problem when taking Bias frames. I had the same problem multiple times.
I have the latest installed kstars-bleeding from the ppa. Hardware is an SBIG ST8XME.
I made a sequence: dark, bias, light. Then made scheduler: go to object, align and capture. He aborts on trying to take the bias after having taken the darks successfully. When I make the whole thing without taking bias-frames no error.
This is piece of logging where error occurs. Last time I had this error too.
indiserver is this one:
2016-08-24T21:01:39: startup: indiserver
Usage: indiserver [options] driver [driver ...]
Purpose: server for local and remote INDI drivers
INDI Library: 1.2.0
Code $Rev$. Protocol 1.7.
The following user(s) said Thank You: Jasem Mutlaq
SBIG does not offer taking bias frames on their cameras - means zero exposure time and shutter closed. You can only take a fake bias with the shortest exposure time available. AFAIK the bias is taken into account internally in the camera.
An alternative that I do is to just subtract the master dark frame from the light frames. Since it includes the bias, it has the same effect as subtracting the master bias frame from both the light frames and dark frames and then subtracting the master dark frame from the light frames. Now if you divide the light frames by flat frames, there can be an issue because then you are no longer just subtracting and the bias would not just cancel out. One solution is to subtract dark frames from the flat frames first so there is no bias in the flat frames. They of course would be much shorter darks (almost bias frames). This would allow you to not even have to worry about actual bias frames.
Bias frames are absolutely supported within the driver. This was a copy/paste error and is now fixed. Thanks for the report! You can test it again tomorrow.
Page 11 of the SBIG Universal Driver docu states that whenever you request an exposure shorter than the minimum exposure time (which is always greater and never equal to zero) you get an image with minimum exposure time and this is never a real bias! You may say that the INDI driver supports it by requesting a zero exposure image from the cam but what you get is different from what you expect. Correct me if I'm wrong but than please give me the technical details of how to get a real bias from my ST402. BTW, the SBIG Windows app does not offer taking bias images, at least not in an obvious way. Imagine why.
It is captured at the minimum exposure length offered by the camera. The error reported above is not related to this issue but a simple programming error. I will add this information about the bias frames to the SBIG driver page so that folks are aware of this issue in case they opt to take a "bias" frame.