We took a number of images of M35 during our test run on Feb 27, 2013. All images were taken through the R-band filter, and had exposure times of roughly 20 seconds (but the shutter was opened and closed by hand).
The best focus position was somewhere around 32900 on the ACE control system's readout. We took one image far below this value, at 32600, and one image far above this value, at 33200. I've cut out small portions of these out-of-focus images and display them below. The portions come from the northeast (A), northwest (B), southeast (C) and southwest (D) corners of the image. In all the little cutout images, North is up and East to the left.
Image 50, taken with focus = 32600.
A = northeast corner.
B = northwest corner.
C = southeast corner.
D = southwest corner.
Image 51, taken with focus = 33200.
A = northeast corner.
B = northwest corner.
C = southeast corner.
D = southwest corner.
You can compare these images with those taken with the S2KB camera on Mar 01, 2013. We used the same filter (R) and pointed at the same field, M35. We used a 20-second exposure time, similar to the exposure in the HDI images.
We found a best focus of 33,200 units for S2KB. We then moved the focus to two very different values:
Recall that the HDI pictures were thrown out of focus by a small amount, roughly 300 units above and below best focus.
The picture below shows a zoomed-in view of small regions from each corner of the image at focus 32500 units (below the best value). The orientation within each image is North up, East to the left, and the arrangement of the closeups is the same: the top-left closeup is the North-East corner, the bottom-right closeup is the South-West corner.
Image with focus 32500 (below best by 700 units):
Next is the image taken at focus 33900 units (above best by 700 units):
