Camera Readout Options

The RCT CCD camera comes with a large number of possible combinations for readout. The observatory control software provides a variety of choices which feature:

1. Binning the pixels by 2, 3, or 4 in columns and rows
2. Windowed readouts of various CCD subarrays
3. Readouts through single amplifiers or all four.
4. Different gain settings
5. MPP mode (or not)

The FITS images written by the RCT Camera are 16 bits per pixel of unsigned integers (integers up to 65535). The following table lists the supported readout modes about which significant information is known:

Table 3.4: CCD Readout Modes

Mode #	binning amplifiers	MPP	read time (sec)	image size (colxrow)	file size (MB)
1	1x1	ALL off	30.1	2200x2048	9023
2	1x1	ALL on	30.1	2200x2048	9023
3	2x2	ALL off	9.1	1100x1024	2267
4	2x2	ALL on	9.1	1100x1024	2267
7	4x4	ALL off	3.5	550x512	577
8	4x4	ALL on	3.5	550x512	577
9	1x1	C off	117.8	2200x2048	9023
10	1x1	C on	117.8	2200x2048	9023
11	2x2	C off	33.7	1100x1024	2267
12	2x2	C on	33.7	1100x1024	2267
13	3x3	C off	17.4	733x682	1014
14	3x3	C on	17.4	733x682	1014
15	4x4	C off	11.5	550x512	577
16	4x4	C on	11.5	550x512	577

The 4 amplifiers are denoted A, B, C, D and each resides on one corner of the CCD. Using all four amplifiers results in reduced readout times; if all other settings are equal, the readout time can be reduced by a factor roughly inversely proportional to the number of amplifiers used.

For readouts through all 4 amplifiers or the C amplifier, the cardinal directions in the resulting image are the same. The figure below shows the locations of the amplifiers and the cardinal directions. Pixel (0,0) is located in the same corner of the CCD as amplifier C.

Figure 3.5: Location of the amplifiers and the cardinal directions

If the image is readout with all 4 amplifiers simultaneously, the orientation is the same as shown in the figure (and the same as an image readout through 'C' or 'CD').