CCDS Slit-Viewer Image Artifact

Friday, May 10, 2019 11:24 AM

Problem(s) Encountered:

There's a strange vertical shadow on the slit viewer that wasn't there in the afternoon or early evening.  It is easily confused with the slit, which has a slight tilt and is thinner and often invisible.  There's also a dark  black hole  shadown taking up much of the center of the slit viewer field.  Sometimes when one can actually see things without these features, one finally sees a black spot near the center of the field that seems to be bad pixels or something.  These features all obliterate much of the field obstructing the use of the finder.


The vertical shadow is, I believe, an artifact of running the camera with the shutter ‘permanently open’.  It does not seem to appear if the shutter cycles for each exposure.  This can be adjusted by clicking the options arrow (expose or guide tab)>camera settings and clicking ‘open’ or ‘close’ shutter.  I currently have it set to cycle for each exposure (close shutter).
I’m not sure what the “black hole shadow” is for sure, but it looks strikingly like a burned-in negative of a previous image of an extended object.  It was there when I checked the camera this morning.  Cycling MaximDL appears to have made it go away.  There might be a simpler way to flush the chip, but I’m not that familiar with MaximDL.  If it happens again, I’d suggest cycling MaximDL, reconnect, turn on the cooler and try exposing again.