90prime fact sheet from Sept 30 2010
Note, this document is a bit more than 72 columns wide.

                                   WEST
          ____________________________________________________________
          |                         |  |               |   amp       |
          |                         |  |               |   16        |                                                      
          |         CCD             |  |       CCD     |             |
          |           3             |  |        4      | ----------- |                             
          |                         |  |                             |                             
          |                         |  |                             |                             
          |_________________________|  |_____________________________|                             
 NORTH    |_________________________   ______________________________|   SOUTH                                                     
          |                         |  |                             |
          |                         |  |                             |
          |       CCD               |  |          CCD                |
          |        1                |  |            2                | 
          |                         |  |                             |
          |                         |  |                             |
          |_________________________|__|_____________________________|

                                  EAST


Chip4 has only 1 good amp (amp 16), other 3 turned off.
As of Sept 30, to display image properly in quick look (automatic) or
ds9, invert xy has to be on. In MSCDISPLAY, no invert has to be turned on.
This will get fixed.

Offset from center of the 4 CCDs (the center of gutter) to center of chip 1:
move the telescope1006 arcsec SOUTH (ie, -1006)
move 908 the telescope arcsec WEST (ie, -908)

Each CCD is 4032x4096 physical pixels, 15 micron pixels, approx 0.45 arcsec/pix

Each CCD has 4 amps, each amp is 2016x2048, but each amp has overscan,
so before processing each amp is 2036x2048 (ie, (2016+20 overscan)x4096)

Gain is about 1.7-2 (see header)
Readnoise is less than or about 10 electrons (see header)

Nonlinearity starts about 60,000 data numbers.
We took flats shooting for 30-40k for no obvious reason.
(Remember you can take images as short as 0.01 seconds with no problems)

The focal plane is pretty flat. Quite flat internally, and we've gotten it pretty
flat on the sky. On-sky flatness can be improved.