Guide Camera Cycle Time


I am using an SBIG-8300M camera with PHD2 using the SGP Api Guider. I observe that when using a 0.5 second exposure time in PHD2, I can hear the shutter on the built-in guide camera cycle at a rate faster than once a second. But examining the PHD2 Guide log and the Debug log, these show that the cycle time for image, download, analyze and ouput corrections is happening at a cycle a little over 2 seconds, with most of the time between issuing the command to take the image and getting the response.

Why am I hearing the shutter cycling much faster than the commands from PHD? Might SGP be commanding repetitive exposures at 0.5 seconds rather than waiting for a command?

Fred Klein


If this were the case then your guide images would also look very suspect as the CCD would still be acquiring data as it was being downloaded.

For each frame you should hear the shutter open and shutter close and then a pause until the next frame while the image downloads.