The 2048x2048 CCD is a very large CCD which produces images that strain the capability of a Microvax II. The limits on memory, bus speed, and CPU speed are all apparent in dealing with such large arrays. Patience is required. It takes about 5 minutes to read out the CCD itself and to store the resulting 8 Megabyte frame on disk.
At the present time, due to limitations in the camera tables, this CCD must be used as the engineering CCD (i.e. dewar number 0). Use a size of 2048x2048 pixels, plus whatever overscan you need. Images have been read out at 2100x2100 pixels without problems. Although binning is remotely supported, the camera tables for CCD 0 are not correct for this camera. Thus, to get a 4x4 binning (useful for test exposures, as it reads out much quicker than the full image), use binning pattern 6, and define the chip size as 530x530 using CAMERAS. If you do not redefine the chip size, the binning will occur at the camera, but the software will try to read a full 2048x2048 frame. This will be fixed once the camera tables are enlarged past their present limit of only ten CCDs.
IMAGE is very slow for such large frames due to the way the
calculation of a pixel value is done. Specifically IMAGE averages the
relevant box of n x m pixels which form a single pixel on the
display monitor. Since n and m are both 4 or larger for a 2048 x
2048 frame displayed on a 512 x 512 pixel display, a new word has been
written, BIGIMAGE, which does no averaging at all, but just displays
every nth and mth pixel. BIGIMAGE is in all other ways identical
to IMAGE.
At the P60, a special shutter has been constructed for use with the
Tektronix 2048x2048 CCD. The normal shutter is too small to be used
without substantial vignetting. Even the 2x2 inch filters in the P60
filter wheel are just a little too small to be used without a small
amount of vignetting. This shutter is installed on top of the P60
direct imaging base, and has a somewhat different control path than
the normal shutter. A series of lower level words which control the
large shutter, designed by Phil Friswald, have been written, called
FRISPREP, FRISOPEN, and FRISCLOSE. FRISPREP must be used to
initialize the shutter when it is first powered up. The higher level
commands TEKFOCUS, TEKMULTIPLE, TEKSNAP, and TEKTEST use this shutter
instead of the normal shutter. (Note that CONSEC will fail to work
with this CCD as there is insufficient memory in the Microvax II CPU.)
This large shutter is not as robust as the normal shutter, nor does it open or close as rapidly. So exposures shorter than 5 seconds cannot be regarded as accurately timed. (The regular shutter opens sufficiently rapidly that timing is accurate even for exposures of 1 second.)