Red Barn Observatory MPC/IAU H68
Established 2006
This Web site is best viewed with a resolution of 1280x1024
A Method To Further Cool A SBIG ST-7 CCD
The heat and humidity of the Southeastern United States can (at times) cause lots of trouble when it comes to CCD imaging. During the summer months, daytime temperatures can easily break the 100 degree mark with the low temperatures at night only reaching the middle to lower 80s. This can play havoc on a CCD imager and really cause it to strain just to keep the internal CCD chip temperature at a "normal" 0 deg. C. A CCD chip must be cooled to properly work; the cooler the chip, the less noise produced. Many CCD imagers have "built-in" systems that allow the cooling to be assisted by means of cold water. The water flows through the camera body and behind the chip inside, causing the internal temperature to drop, and assists the electronic peltier device inside allowing it to drop it's temperature by many degrees. Many camera's (such as mine) do not have the option of water assisted cooling installed. To have the water cooling system installed, one must return the camera to the manufacturer to have the upgrade, or come up with your own custom idea for cooling as I have done.
My custom cooling modification was simple, cheap, and is very effective. With an outside temperature of ~85 deg F, my ST-7 will self-cool down to 0 deg C but it must produce a power level of 90% - 95% to maintain this temperature. With a power level that high, the camera is under strain. Once the cooling modification is in operation, it will drop the internal temperature of the camera to -10 deg C and produce a power level of ~ 80%- 85% which in my opinion is a safe "power load" on the camera. During the very late night/early morning hours when the night air cools, this power level will drop to below 60% allowing the camera an easy working condition.
Condensation will form on the copper tubing but I haven't found it to be a problem (other than dripping on the carpet occasionally.) Every thirty minutes or so, I journey into the scope area of the observatory to check on things, and when I do I just take a small towel and wipe off the condensation. The condensation will not affect the camera, although I try to avoid any condensation from getting around the cable connections.
The image below shows a close-up of my SBIG ST-7 with the cheap, easy modification for further cooling the unit.
This minor modification is easily done and can greatly drop the internal temperature of the camera. All that's needed is a small water pump, copper and nylon tubing, a bucket or ice chest, and ice water. The copper tubing should be wrapped around the cooling fins of the camera. This simply further cools the cooling fins and allows the internal temperature to drop. The weight of the copper tubing along with the water only adds somewhere around 12 ounces to the telescope so the extra weight is not much of a concern.
These pictures give a general idea of how the tubing system is routed "out of the way" on my 12" LX200 GPS.
When I first started using the ice water for extra cooling, I was using a regular 5 gallon bucket with plain ice and water. The ice would normally last about 45 minutes or so before having to refresh the icy solution with more ice. I needed something more insulated than the bucket and smaller would also be a big help. I found a Styrofoam box that measured about 14"x14"x14" with a nice thick foam top. 3 to 4 large ice packs can fit inside the cooling box along with the pump and a gallon of water.
Here's a picture of the box (with pump) and a picture of the lid installed on the box. When the temperature begins to drop, simply replace the "thawed" ice packs with fresh frozen ones and place the thawed ones back in the freezer. Ice packs are cheap and easily replaceable.
The total cost of this simple equipment:
6'-5/16" copper tubing $6.00
10'-3/8" nylon tubing $2.50
Water Pump $11.00 - $12.00
Styrofoam box $0.00
Ice Packs $1.00 $2.00 (cheap)
Total Cost: Less than $30.00
Copyright © 2006 The Cometary Space Web of Steve E. Farmer Jr.
Last modified 05/30/2007 06:42 PM -0400
This web site has been active since March 1, 2006
For Information send e-mail to INFO