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12VDC Water Pump Kit
for ST and STL Cameras
August 14, 2008

Using water to improve the cooling of SBIG ST and STL cameras is simple and inexpensive. These cameras generally do not require more cooling than can be accomplished with air cooling alone, but there are exceptions and if you happen to live in a very warm climate you may wish to use the additional cooling that can be obtained with water circulation. All dual sensor ST cameras are already equipped with a water circulation heat exchanger inside the rear of the camera, ready for use. The only thing that is required to use this feature is a supply of water.

Obtaining optimum cooling in hot weather using water circulation requires very little in the way of water pressure or chilling of the water to get the most cooling performance from your camera. You can do quite well with water that is just below ambient temperature. Chilling the water further can help but care must be taken not to chill the water below the dew point or condensation may form in you camera. Fortunately, it takes very little chilling, if any, to obtain more cooling than you will need for most circumstances, and a slow steady flow of water is all that is necessary. Many users do not use water circulation at all. If, however, you image on very warm nights and want to get the most cooling you can get, our 12VDC water pump kit includes everything you will need to achieve sufficient cooling for any climate. The kit includes a 12VDC water pump mounted on a thick anodized aluminum plate so the pump can simply be placed at the bottom of an reservoir of water without further attachment. The pump's power cord terminates in a cigarette lighter adapter plug for convenient use in a variety of field power supplies. The plug has a convenient on/off switch on the back. In the alternative, this plug can be removed and the cable attached directly to a 12V battery. The connector at the pump can also be used with an optional universal 100- 240VAC to 12VDC power supply (the same power supply we use for the ST-402ME camera).

The setup is simple. Just push each of the two supplied tubes over the water connectors on the back of the camera. Connect the other end of one of the tubes to the pump. The end of the other tube will just lay in the water reservoir for returning the water from the camera. Fill a reservoir with some water at ambient temperature or a few degrees below ambient. Place the pump in the water and plug it in.

The graph at right shows the results of a random test performed on a stock ST-8XME camera pulled from the shelf. The camera was set up with water circulation ready, but the pump was off. The reported temperature of the CCD at the start of the test was just under 25 degrees C. The room temperature was reading 23.5 (+/- 1.5 degrees). The camera was first cooled to the maximum it would reach with air only then the water pump was turned on and the camera allowed to cool further until it leveled out at -25.4 C, or a delta of approximately -50 degrees C. at 100% TE cooler power. At 86% power to the TE cooler, with water circulation, the camera would regulate the cooling at -22 C, or a delta of about -47 C. This is with water at just a few degrees below room temperature, 20C or about 68F.

It should be noted that the cooling performance can vary from camera to camera, and this is a single test. For this reason we state that the "typical" cooling performance of an ST camera is -35 degrees C below ambient with air only and -45 degrees C below ambient with water. This is more than enough cooling to reduce the dark current noise of any ST camera well below the sky background noise in the vast majority of cases, even when using narrowband filters, on warm summer nights.

As of the date of this announcement (8/14/08) the 12VDC water pump kit list price is $129 but is being offered for free with new self-guiding ST cameras as part of a special offer. SBIG also offers a smaller pump that is powered by 110VAC (only) for ST cameras for $49. Please see our Price List for current prices.