CFHT, Instruments, Imaging, FOCAM, Data Acquisition.

Canada-France-Hawaii Telescope

A User's Manual for the CFHT Visible Imager: FOCAM

CCD Data Acquisition User Interface: FOCAM


This section describes solely the FOCAM related computer user interface. A detailed description of the general CCD data acquisition user interface, is given in " A Users's Manual for the CCD Data Acquisition User Interface@", accessible via the hyperlink.

Sign On

Users may sign on to the HP9000 system by typing focam after the login prompt, and then typing the password of the day. Check with your support astronomer or the telescope operator for the password in use for your run.

The login process creates the appropriate icons and windows, including a top menubar: the Pegasus session manager. See the " A Users's Manual for the CCD Data Acquisition User Interface@", hyperlink for a detailed description of the data acquisition environment.

Beginning of Night Check up

Check that the RASTER is properly defined and corresponds to the CCD in use. Check that the disc meter indicates a large enough available disc space for your night of observation. A 2Kx2K CCD image represents 8 Mbytes of data.

FOCAM Control

The only FOCAM control available, and the only one you need, is the filter wheel control. This is done easily by clicking in the FOCAM button on the menubar (opens the FOCAM window, see this figure), selecting the appropriate filter by clicking in the box in front of the correct number and identification, and clicking "accept". A working icon "focam working, please wait" will appear during the time needed for the filter wheel to rotate to the requested position. An "abort" button is available in this working icon to allow you to interrupt the filter rotation if needed. Each position number has an associated filter description which has been entered by the support staff prior to your run. This filter descriptor is written to the FITS header of your image together with the filter position number.

CAF: Computer Aided Focus

This tool has been specifically designed for fast focussing during imaging observations. In its fully automatic mode (prime focus), it takes a sequence of exposures, moving the prime focus bonnette focus between each exposure, measures the image FWHM for each, displays the measurements for your review, computes the best focus, and moves the prime focus bonnette to it. A partially automated version of CAF has been implemented for the Cassegrain focus (no computer control of the telescope focus). See the section Focussing of the next Mosaic page for a full description of the focussing procedure.

Clicking into the CAF button on the menubar will open a window like this one, the CAF form, in which you may enter the following fields:

  • Time: exposure time in seconds
  • Frames: number of frames (between 3 and 8)
  • Delta Z: focus increment on the prime focus bonnette between each exposure (between 0.01 and 0.25 mm)
  • After your clicking into the "accept" button, the focussing sequence starts.

    Please send comments to Dennis Crabtree at