Cooling the Meade DSI IIc with a Peltier Chip

28 May 2014.  I tried to get an image last night, but the attempt was foiled by persistent clouds and wind: the Clear Dark Sky forecast was not very accurate last night.  I did get to play with the “new and improved” chiller setup for my DSI IIc camera, so I thought I’d report on that.

I wish this idea were original to me, but it certainly is not.  A couple of years ago I decided to follow others’ leads (I googled Peltier cooling of Meade DSI cameras, and I hit on a web site that gave me some ideas (http://www.backyardastronomy.net/peltier_cooling.html)).  This guy used an inexpensive Peltier kit with a computer CPU fan to cool down his DSI.  I decided to try it.  I milled off the back of the heat sink so I’d have a flat surface where the Peltier could be attached, right above the “cold finger” that cools the back of the CCD.  I put a salvaged CPU cooler fan (~$5) on top of the Peltier, to carry heat away from its hot side.  Thermal paste is applied to all surfaces that need good thermal conductivity (CCD/cold finger, heat sink/Peltier, and Peltier/fan heat sink). Last fall I added insulation around the outside of the camera and switched to a smaller Peltier chip (TES1-12704, ~$5) that is a bit better matched to my power supply (~$80 for a current-regulated supply).  The temperature (as reported by Nebulosity’s DSI control code) vs. current performance is shown below.  That got things cold enough that I was having issues with dew and frost, but my big mount failure and winter intervened (I don’t cool the camera when Utah nights keep it cold without any artificial intervention).  To combat the moisture (which really isn’t bad at my site; after all, all of Utah is desert) I loaded 4 small desiccant packs (about $0.10 apiece) inside the camera body, and after watching numerous rubber bands rot and fall apart, I used cable ties to secure the cooling fan and Peltier chip to the camera (I’ll have to add a picture of that later).  Anyway, the bottom line is that for less than $100 this rig lets me cool down to about 15 °C below ambient and significantly decreases the noise on those hot summer nights.  

The milled-off heatsink back of my DSI IIc camera

Peltier chiller performance.  I tried a couple of different heat sinks, and the larger, higher capacity sink worked better.