ALFOSC shutter

The minimum time to open and close the shutter is about 0.3-0.4 seconds (Figure 1).
So, one ***can _not_ take*** an exposure shorter than 0.3 sec.

The shutter pattern is virtually non existent. Several 0.2 and 5 seconds overscan subtracted images were coadded and
normalised to one second. The ratio of the long and short images indicates that there is a slight gradient from bottom left to
top right hand corner. However, the difference between the corners is less than 1 part in 1000 for a 0.2 sec exposure.

Fig.1 integration time versus measured count level (using Beta light) from overscan subtracted image.
Click here to see large image.