Peltier Cooling of Modified Canon Digital Rebel XSi (450D)

Version II


by Gary Honis

The first version of the cooling system I made for the Canon modified 450D did not cool the camera as well as I liked. It used a coffee canister as the cooling chamber and its metal was not a good conductor. I then rebuilt the cooling system but this time I used part of the original cooler for the cooling chamber, instead of the coffee canister and it is Version II.

UPDATE: See latest Version III of the cooler that is smaller, lighter and cooler HERE.

The original Cooler is branded "RubberMaid" but the cooler is made by Vector, Inc. and branded under other names as well. It operates on 12 volts DC and Vector also makes a 6-Amp AC/DC converter to operate the cooler using 120 volts AC.

Below are some quick images of how I used a peltier device from the 9 can beverage cooler ($25) along with a styrofoam cooler ($3) to build a peltier cooling system for my modified Canon XSi (450D).


In the image below the peltier cooled Canon XSi (on right) is in the focuser of an Astro-Tech 127mm triplet refractor. In the background is a Meade DSI Pro imager in the focuser of an Orion ED80 used for autoguiding:

The following photos were taken during the assembly process:

Peltier cooler parts taken off the cooler. Although this photo shows the peliter device removed (part with white thermal paste), the peltier device does not need to be removed for this version of the camera cooler and is left in place untouched. Only the black fan and switch are removed.

Fan remounted to heat sink:

The cooler's on/off and cold/warm switch with LED lights was taken off cooler and mounted in a project box:

The original cooler is cut in half with a hacksaw so only the aluminum chamber of the cooler remains:

Holes are made for the 2" Barrel to focuser and for the camera's flash nosepiece:

Fan is reinstalled on peltier heat sink and switch mounted in project box is attached to a cooling fin:

Wires with 12 volt DC from project box run to two fans inside aluminum chamber. Hole drilled in chamber base for camera tripod socket thumbscrew:

Heatsink mounted on aluminum chamber with thermal paste and screw near camera:

Completed Cooler - fan side view:

Completed Cooler - bottom view with camera tripod socket thumbscrew:

Completed Cooler - Front View:

Completed Cooler - Top View:

Completed Cooler - with lid open:

Closeup of inside of completed cooler:

Image of cooler on scope:

I used two temperature probes to test the cooling effect while taking dark frame images. One probe was placed on the aluminum chamber wall and the other on the camera body as shown below:

I took ISO 1600 dark frames every five minutes and measured the air temperature inside the cooler at the two probe positions. The ambient temperature during testing was controlled and varied over the four hour period from 76.8 degrees Fahrenheit to 77.9 degrees. It averaged 77.2 degrees. A plot of the 38 degree Fahrenheit temperature drop over time is shown in the chart below:

I was pleased with the above temperature drop over time as measured by the two probes. Still, what is the effect on the dark frames taken? For the graph below, I converted the ISO 1600 Canon five-minute dark frame raws to TIFs using Canon's Digital Photo Professional and then recorded the standard deviation of the whole color image (4272 X 2848 pixels) for each dark frame:

Notice in the above graph that noise increases over the first ten minutes (the first two 5-minute exposures). It shows the delay in cooling of the camera's imaging chip and electronics. I'll have to do a test with no cooling (camera outside of the cooler) and add the results to the above graph to see how much of a benefit the cooler provides over non-cooling.

Dark Frames - Animation and Stills:

This animation is made with the 342 pixel X 342 pixels crops from the center of the five-minute dark frames (4272 X 2848 pixels) at ISO 1600 taken during the above cooling test:

Below is a comparison of the 342 X 342 pixel center crops of the five-minute dark frames at ISO 1600 taken at ambient temperature (77.2 degrees Fahrenheit) and after one hour of cooling ( 45.5 degrees) and two hours of cooling ( 40.5 degrees):

UPDATE: See latest Version III of the cooler that is smaller, lighter and cooler HERE.

Removal of Canon XSi (450D) IR Cut Filter for Astrophotography:




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Astro Imaging with Canon Digital Rebel XT Camera