[Elphel-support] Elphel NC353L long exposures

[Niko Lavonen]

Hello,

We here at Metsähovi Radio Observatory acquired an NC353L camera earlier 
this summer for all-sky monitoring of weather conditions. Overall we've 
been pleased with the camera, but there is a problem with long exposures 
we've not been able to figure out. It seems the camera won't do exposures 
longer than approximately 38 seconds. Is there a known limitation in the 
camera's hardware or software that imposes this limit? To get a view of 
the night sky, we'd very much like to have the camera do exposures for up 
to many minutes if needed.

We've observed that when the camera reaches the "maximum" exposure time, 
it starts reporting that the exposure is 1/1000000 seconds, while it can 
be seen from the images that the actual exposure is still in the order of 
many sedconds. We've tried raising the AUTOEXP_EXP_MAX value higher than 
the ~38 second limit, but the camera won't go higher. We've also tried 
manually setting the exposure time to e.g. 60 or 120 seconds, but in 
these cases the camera has frozen. Our camera firmware version is 8.2.7.

Regards,

Niko Lavonen
Research assistant
Aalto University Metsähovi Radio Observatory
Metsähovintie 114, 02540 Kylmälä, Finland
e-mail: nlavonen at kurp.hut.fi
Phone: 029-4424856