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Note:
The Guider Port outputs employ optically isolated solid-state switches that mimic the
traditional behaviour of the older technology mechanical relays. The optical isolation prevents
potentially interfering or damaging ground loops between the camera and the mount.
This newer approach is completable with most modern telescope mounts that employ logic
inputs pulled to VCC with a suitable load resistor.
Caution:
Do not apply more than 50v or 50 mA to the guider port pins. The ‘Common’ input
must be at ground or zero volt potential relative to the control input of your mount. Contact QSI
if you are uncertain about your mount’s electrical characteristics.
Cooling the Camera
Cooling the CCD is essential for successful long exposure imaging. Cooling the sensor
dramatically reduces the dark current and resulting thermal noise in an image and makes long
exposures practical. See the discussion in the CCD Imagin g Overview Section on dark current
and noise.
QSI 600 Series cameras use a very efficient thermo-electric cooler (TEC) which relies on the
Peltier Effect to cool the CCD. When power is applied to a TEC, one side of the device gets
cold and other side gets hot, essentially pumping heat from the cold side to the hot side. All QSI
600 Series cameras employ a two-stage TEC to increase the differential cooling effect.
The more power applied to the TEC, the greater the differential cooling and the colder the CCD
can get. The heat pumped from the CCD, as well as the power dissipated by the TEC, creates a
significant amount of excess heat that must be removed from the camera. QSI 600 Series
cameras employ two different methods for removing this heat.
Standard air cooling
The back of a QSI 600 Series camera acts as a large heatsink with cooling fins machined
directly into the body. Two automatically controlled cooling fans force air through these fins. The
movement of air through the cooling fins greatly increases the amount of heat removed from the
camera.
Keep in mind that the lowest temperature that the CCD can be cooled is limited by the ambient
air temperature and the speed of the cooling fans. Achieving very low temperatures is easy
when imaging outdoors during cooler weather. If it is particularly cold you may not even need to
turn the fans on. If the weather is warm and humid you may not be able to cool the CCD to the
desired temperature. See the specifications for your camera to determine the maximum cooling
differential you can expect under typical conditions.
