For the past few weeks I have been working on a method to cool a digital camera. My camera is the Canon 10D. As we all know, the dark noise of the camera chip is reduced by a factor of about 2 for every 6 degrees Celsius reduction in the camera temperature. This equipment is able to reduce the temperature of the camera by 24 degrees below ambient. Thus at room temperature, 22 Celsius, the camera can be cooled to 0 Celsius. This gives a reduction in the dark noise generated by the camera of about 16 times.

If one has selected a camera with excellent low noise in the first place, this amount of reduction in the noise reduces it to a point where is almost not a problem at all. Obviously this is a significant advantage with hot summer nights. Of course, on colder nights, the camera temperature can still be lowered by 24 Celsius and thus temperatures well below freezing can be accomplished.  The 10 D will operate to temperatures well below freezing.

Lowering the temperature is attained with a liquid cooled by a Peltier cooler package and pumped from the Peltier unit to the heat exchanger integral to the cooler box. The liquid used is ethanol alcohol and water in proportion to prevent freezing of the liquid. The cooler is a totally enclosed aluminum box which holds the camera and which has a built in heat exchanger. The box runs close to the temperature of the coolant.

Since the box is totally closed and very well insulated, there is no condensation within the box and little heat flow from ambient to the box. The camera is inside the box with power and control cables run out of it to a computer and exposure controller.

The cooler box is designed to go on the back of our 12 inch LX200 telescope. The connecting element is designed to take a simple filter or a focal reducer. It is made of black, opaque delrin to reduce heat flow from the back of the telescope to the cooler box.

A photo of this cooler attached to the Doc G telescope is shown below.

 

The cooler system is shown in closed and open situations in the two final photographs below.   In the closed condition, only the fan which drives out the heated air from the Peltier unit protrudes above the lid.   The hot air from the Peltier cooler and its power supply exit from the front and rear sides of the cooler system box.  A dual thermometer is located on the top of the box so that the operator can keep track of the functioning of the box.

In the open condition, which is not the operating condition,  the Peltier cooler can be seen on the right with its power supply,  This compartment is separated from the cold side of the cooler system box with insulating material.  On the left is the Eheim pump which moves the cooled liquid and a reservour which de-gasses the coolent.  The coolent than moves through the instant disconnect couplings, through the connecting tubing to the camera cooler box located on the telescope.