Useful files

This page documents some files that may come in useful while observing or during reduction.

CCD defects

The HiPERCAM CCDs have a number of defects, dust and the like, and, as of 21 May 2018, a hair in the lower-left quadrant of CCD 4. When acquiring targets these may not be visible so you are strongly advised to plot a file of defects. You can also create your own using the pipeline command setdefect and you are encouraged to do so if you see a defect not already marked in whatever file you use.

Defects are classified as “moderate” (plotted in yellow) or “severe” (red). What one counts as one or the other is a matter of taste. If you are too picky, you could end up with so many defects that youare afraid to observe.

I have decided to define defect file according to the following prescription: moderate: 10 to 25% deviation from the norm; severe: greater than 25% from the norm. I mark each pixel in these categories, so a really bad feature might appear in multiple pixels (there is a very nasty feature in the lower-right of the lower-left quadrant of CCD 2 for example). I plan to update the file with time, and retain old ones for monitoring purposes. I identified the bad pixels using a flat field divided by a smoothed version of itself (smoothed with a 20 pixel FWHM 2D gaussian filter).

When observing, you should move the target and essential comparison stars away from any such defects, particularly those that appear in red.

Files:

  1. 2018-05-21 (hipercam defect file)

  2. 2018-06-02 (ultracam defect file)

  3. 2018-06-21 (ultracam defect file) Added another bad column in CCD 2

  4. 2019-12-08 (ultraspec defect file)

Warning

For ULTRACAM I need also to add hot pixel defects which need to be regarded differently to flat field and poor charge transfer defects as a poor hot pixel could be very bad for a faint target but not matter much for a bright one.