QSI 520c Betriebsanweisung PDF herunterladen (Seite 18)

QSI 500 SERIES USER GUIDE

There are numerous ways of supplying recirculating water for the camera. One of the

simpler and more common methods for astro-photography is to place a small submersible

pump into a 5 gallon plastic pail full of cool water. The temperature of this amount of water

will rise by only a few degrees after a full night of imaging. For additional details on the

Liquid Heat Exchanger, see the Accessories section below.

Note: The Fans can usually be turned off when using the LHX. In fact, the fans

may actually decrease the cooling ability if the air is warmer than the liquid.

Caution: It is generally advised that only water be used in the LHX. Coolants

such as ethylene glycol and some solvents may damage the seals and gaskets.

Additional cooling tips can be found in the QSI Knowledge base on the QSI web site:

http://store.qsimaging.com/kb_results.asp?ID=6

How Much Cooling Is Enough

Good results can be obtained with the CCD cooled to -10ºC when taking modest length

exposures. This is easy to achieve with forced air cooling when the ambient air is at 25ºC

(77ºF). For most CCDs used in QSI 500 Series cameras, dark current is reduced by half for

every 6ºC drop in the temperature of the CCD. Cooling from 26C to -10ºC results in a 64-

fold decrease in CCD dark current. For more demanding imaging and longer exposures,

lower temperatures are desirable. Cooling the CCD another 12ºC to -22ºC lowers the dark

current further to just 0.4% of the dark current at 26C. Cooling below -30ºC results in a

diminishing improvement as the noise from the dark current is outweighed by the intrinsic

read noise of the CCD itself. The camera will actively prevent the CCD from being cooled

below -40ºC.

Fahrenheit -40F -20F 0F 20F 32F 40F 60F 80F

Celsius -40C -29C -18C -7C 0C 4C 16C 27C

Note: Refer to the specification sheets at the end of this Guide for the exact

cooling specifications for your particular camera model. Keep in mind that

ambient temperature changes, air movement, and even relative humidity can

affect the temperature that the camera can reach and maintain.

Note: The cooler is not designed to raise the temperature of the CCD above the

temperature of the camera body, i.e. it can not heat the CCD. If the ambient

temperature is -10ºC, the cooler can not bring the CCD temperature up to 0ºC.

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QSI 520c Betriebsanweisung Seite 18