Verify CCD operation

 In order to test the CCD, you should first confirm that the system has been configured to use the correct camera. This is usually done by the Palomar staff, but it should be checked as follows:

The cameras command controls other CCD options as well, including the binning pattern. A notable option within the cameras command is the configuration for dewar #0. This is an engineering setup with which you may want to experiment, for example, to extend the overscan region (which is almost non-existent in the default configurations for CCDs #15 and #16). However the default configurations will often be sufficient.

Once the camera is configured, check the temperature indicators on the monitor to verify that the dewar is cold (T ~ -100 K). Then test the CCD by taking a 0-second test exposure:

After the readout interval, this exposure should appear on the monitor and resemble a bias image, i.e., random noise with a mean level of a couple thousand counts. If the image appears suspicious in any way, notify the Palomar crew to make sure the camera is functioning properly.

You will probably next want to test the camera with a slightly longer exposure, i.e., 2-10 seconds. There are a few telescope-specific issues to consider for this test:

• 60-inch
  Make sure you have removed the telescope cover and extinguished the lights in the dome. Light leaking in through the dome shutter and/or the calibration lamp emission should be sufficient for tests at this stage.

• 200-inch
  If the dome lights are still on for some reason (e.g., it is earlier than 4:00 p.m.), the exposure should be kept very short, and the mirror cover should be left closed. If the dome lights can be extinguished, do so, and then ask the Palomar crew for help opening the mirror cover. This procedure is easily done from the control room, but the crew should be notified, since certain operations are prohibited when the mirror cover is open (e.g., ascending to prime focus). If the calibration lamp has been installed, you may want to turn it on, although light leaking in through the dome shutter will probably be sufficient.

Then set the filter wheel to an empty slot and try a short (e.g., 3-second) exposure:

The image should show light illuminating most of the field, possibly with a vignetting pattern around the edge indicating the extent of the filter cell. If this is not the case, consult the Troubleshooting section (3.9.5) below. If the image is saturated, i.e., pixel values greater than 2¹⁶-1 = 32767, you may want to reduce the exposure time and try again.