Section 2 - Introduction to CCD Cameras
Page 28
Table 2.1 below lists some interesting aspects of the CCDs used in the various SBIG
cameras.
Camera
CCD
Array
Dimensions
Number of
Pixels
Pixel Sizes
TC211 Tracking CCD TC211 2.6 x 2.6 mm 192 x 164 13.75 x 16 µ
TC237 Tracking CCD TC237 4.9 x 3.7 mm 657 x 495 7.4 x 7.4 µ
ST-5C TC255 3.2 x 2.4 mm 320 x 240 10 x 10 µ
ST-237A TC237 4.9 x 3.7 mm 640 x 480 7.4 x 7.4 µ
STV/STV Deluxe TC237 4.7 x 3.0 mm 320 x 200 14.8 x 14.8 µ
ST-6B TC241 8.6 x 6.5 mm 375 x 242 23 x 27 µ
ST-7E/XE KAF0401E 6.9 x 4.6 mm 765 x 510 9 x 9 µ
ST-8E/XE KAF1602E 13.8 x 9.2 mm 1530 x 1020 9 x 9 µ
ST-9E/XE KAF0261E 10.2 x 10.2 mm 512 x 512 20 x 20 µ
ST-10E/XE/XME KAF3200E 14.9 x 10.0 mm 2184 x 1472 6.8 x 6.8 µ
ST-1001E KAF1001E 24.6 x 24.6 mm 1024 x 1024 24 x 24 µ
ST-2000XM KAI2000M 11.8 x 8.9 mm 1600 x 1200 7.4 x 7.4 µ
Table 2.1 - Camera CCD Configurations
The CCD is cooled with a solid-state a thermoelectric (TE) cooler. The TE cooler pumps heat
out of the CCD and dissipates it into a heat sink, which forms part of the optical head's
mechanical housing. In the ST-7XE, ST-8XE, ST-9XE, ST-10XE, ST-10XME and ST-2000XM
cameras this waste heat is dumped into the air using a new heat exchanger and a small fan. The
heat exchanger is also capable of water circulation for additional efficiency if needed in hot
climates. An inlet and outlet are provided at the back of the camera head for passing water
through the heat exchanger. Only a very small flow is required and an ordinary aquarium
pump is sufficient if it will pull the flow up the length of tubing you might require at your
installation. An optional 110VAC pump and tubing are also available from SBIG.
Since the CCD is cooled below 0°C, some provision must be made to prevent frost from
forming on the CCD. The ST-7XE, ST-8XE, ST-9XE, ST-10XE, ST-10XME and ST-2000XM have
the CCD/TE Cooler mounted in a windowed hermetic chamber sealed with an O-Ring. The
hermetic chamber does not need to be evacuated, another "ease of use" feature we employ in the
design of our cameras. Using a rechargeable desiccant in the chamber keeps the humidity low,
forcing the dew point below the cold stage temperature.
Other elements in the self contained ST-7XE, ST-8XE, ST-9XE, ST-10XE, ST-10XME and
ST-2000XM include the preamplifier and an electromechanical shutter. The shutter makes
taking dark frames a simple matter of pushing a button on the computer and provides streak-
free readout. Timing of exposures in ST-7XE, ST-8XE, ST-9XE, ST-10XE, ST-10XME and ST-
2000XM cameras is controlled by this shutter.
The Clock Drivers and Analog to Digital Converter interface to the CCD. The Clock
Drivers convert the logic-level signals from the micro controller to the voltage levels and
sequences required by the CCD. Clocking the CCD transfers charge in the array and is used to
clear the array or read it out. The Analog to Digital Converter (A/D) digitizes the data in the
CCD for storage in the Host Computer.
The micro controller is used to regulate the CCD's temperature by varying the drive to
the TE cooler. The external Power Supply provides +5V and ±12V to the cameras. Finally, the
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