optics-sept-13-20

A montage of a full range (10mm) focus sweep- focus 0 is at bottom left, focus 9500 is at top right.

Each image along a row has a focus +500 from the one before it.

To be concrete, the images in the left most column have, starting from the bottom, foci of 0, 2000, 4000, 6000, 8000 microns.

On Monday Sept 13, the camera was re-installed. I think (!) the tilt box was set to 3mm on A,B,C,D.

The DES r-band. Frames 1924-1942, Object at CCD1 row,col=1430,663. The first two focus positions, 0 and 500

are dummys as the data was not taken.

The best focus is somewhere between 7000 and 7500. This blowup shows the astigmatic flip of position angle.