Test Procedure for NOT CCDs

Following the the procedure to follow to obtain a complete test data set for NOT CCDs as part of the quality management programme.

The test uses the -light which you will find in the filter carousel in the TCS room.

Please note that the -light should be handled with reasonable care. It is quite robust and likely difficult to break, but please treat it with respect. If you do happen to break it, or believe that you may have cracked it, leave the building immediately, leaving the doors open behind you. Try not to inhale while doing so (that is, leave quickly). Call the safety officer. The tritium contents, if released into the air, should dissipate quickly, but I imagine that our safety officer will want to be sure.

The procedure is the same for both ALFOSC and HiRAC, differing only in how the -light is installed in the instrument:

The data collection procedure is:

1. Place the beta light in the filter wheel facing the CCD.
   • ALFOSC: Put the -light in a normal ALFOSC filter holder, but with a retaining ring on both sides. This is because the beta light fitting protrudes out of the back of the holder and will jam against the collimator barrel if it is not moved forward by one retaining-ring thickness.
   • HiRAC: Put the -light in a normal HiRAC filter holder, facing away from the side into which the retaining ring is screwed. It should end up flush with both sides of the filter holder and not protrude above or below or it will snag on the HiRAC filter wheel.
2. Set the CCD parameters to their default state in BIAS (issue a 'reset' so that the CCD is fully read out and unbinnned).
3. Set the filter & grism wheels so that light from the beta light shines onto the CCD without obstruction.
4. Take 4 bias frames (OBJECT=bias).
5. Collect 2 images each of the following integration times:
   ALFOSC: 2, 4, 12, 20, 28, 36, 44, 52 seconds
   HiRAC: 2, 4, 6, 8, 10, 12, 14, 16 seconds
   (OBJECT = 'Noise Test')
6. Collect 4 bias frames (OBJECT=bias).
7. Collect 2 images each of the following integration times:
   ALFOSC: 48, 40, 32, 24, 16, 8, 2 seconds
   HiRAC: 17, 15, 13, 11, 9, 7, 5, 3, 1 seconds
   (OBJECT = 'Noise Test')
8. Collect 4 bias frames (OBJECT=bias).
9. Collect 20 images of integration time 0.1 sec.
   (OBJECT = 'Low Level Flat')
10. Collect 9 bias images (OBJECT=bias).
11. Remove the Beta light and collect 3 dark images of one half hour each.
12. Collect 4 bias images (OBJECT=bias).
13. Note the approximate range of temperatures of the primary mirror cell during this procedure.
14. Write all the data to a CD-ROM and send it to Tim Abbott.

Notes:

• The entire sequence should be collected over as short a period as possible.
• There is a script available called 'NoiseTest' which performs all the steps except 11 & 12 (which must be done without the Beta light in the instrument). (These are available here too, for: HiRAC, and ALFOSC.)
• Steps 11 and 12 are optional if there is not sufficient time.
• The data collected in this programme will be reduced to determine the operating characteristics of the CCD and to identify any changes. The reduced data and a report will be made available on NOT web pages.
• The illumination level should be such that the images of step (7), the low level flats, are 200-300 ADU above bias level. The images with longest integration times should not quite (but nearly) saturate.