QSI 520c Guía de usuario descargar pdf (Pagina 17)

QSI 500 SERIES USER GUIDE

Cooling the Camera

Cooling the CCD is essential for successful astro-imaging. Cooling dramatically reduces the

dark current and resulting thermal noise in an image and makes long exposures practical.

See the discussion in the 'CCD Imaging Overview' Section on dark current and noise.

QSI 500 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 500 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

500 Series cameras employ two different methods for removing this heat.

Standard Air Cooling

The back of a QSI 500 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.

Liquid-Assisted Cooling

Forced air cooling is usually all that is

needed to reach normal levels of cooling.

However, in warm weather or particularly

demanding situations, additional cooling can

be achieved with the optional Liquid Heat

Exchanger, or LHX. The LHX utilizes

recirculating water for more efficient removal

of heat from the camera. All things being

equal, the LHX can provide an additional 7ºC

to 10ºC of CCD cooling. It attaches to the

rear of the camera body as illustrated in the

image to the right. The LHX includes a thin

thermal pad. Place the thermal pad between

the LHX and the camera body. Hold the

LHX and pad in place with the provided

screws.

Water flows through the two hoses, colored

blue in this picture. Self-sealing quick-disconnect couplings are used to attach the hoses to

the LHX so that the hoses can be removed easily without leakage of the recirculating water.

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QSI 520c Guía de usuario Pagina 17

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