# Appendix CFCCD

## APPENDIX I:FILTERS FOR CCD IMAGING

A filter list is available via WWW and will also be found in NOAO Newsletter No. 34. A complete CTIO filter list is also available via ftp. See the WWW home page.

### CFCCD

The 0.9m, 1.5m and 4m CFCCD systems have two filter wheels each holding seven filters up to 3x3 inches square. These wheels are modular, and we have a single wheel which holds five 4x4 filters. This is useful when an observer brings 4x4 filters for use at these telescopes, or it is desired to use a filter which we have in 4x4 size and not in 3x3.

### SCHMIDT

The Schmidt has a single filter bolt which holds five filters up to 4x4 square.

## APPENDIX II: GAIN AND READOUT NOISE CALCULATION

The gain in electrons/adu is usually accomplished using the gfind command (in the contributed package). Here is a cookbook recipe for determining the gain in electrons/adu, for anyone who wants to do all the steps one by one.

1. Take a sequence of 2 bias frames. Make sure that the preflash is set to zero.

2. Take a sequence of 2 dome flats or, better yet, 2 bias frames with a big preflash value (giving a total signal of approximately 1/2 saturation).

3. Subtract these frames as follows:

BIAS1-2 = BIAS1 - BIAS2 (use imarith)
FLASH1-2 = FLASH1 - FLASH2

4. Use the IRAF imstat task to determine MEAN(FLASH1), MEAN(FLASH2), MEAN(BIAS1), MEAN(BIAS2), RMS(FLASH1-2), and RMS(BIAS1-2). Note that it is very important that the stats box be positioned on a region of the CCD free from traps, bad columns, or any bad pixels.

5. Calculate the gain,

e/adu = (MEAN(FLASH1)+MEAN(FLASH2)) - (MEAN(BIAS1)-MEAN(BIAS2)) RMS(FLASH1-2)2 - RMS(BIAS1-2)2

6. The readout noise in electrons is
RON(e) = RMS(BIAS1-2) * (e/adu) / 1.41

Updated on May 28, 2021, 3:09 pm