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email dave@allmon.com

Where I´m at, the dew point is reached each night about an hour after sunset. I have a dew heater on the corrector of the LX, but the front window of the camera fogs over very soon after the camera is powered on. It starts in the center, and takes an hour or so to completely dew over.

Here is a relatively cheap and easy solution for this problem. Auto parts stores sell a rear window defogger repair kit. It is made by Loktite. It comes with a little bottle of conductive paint, and a little brush.

 

I threaded the front cover onto a T-thread (a piece of an off-axis guider) and rotated it while holding the brush on it. Two passes gives it enough thickness. The result will look like this, if you too drink a cup of cappuccino before starting. I used an x-acto with a #16 blade to clean up the inner edge for appearance, and to trim the resistance to around 40 to 50 Ohms. This gives you about 1.25 Watts at 7 Volts.

The wires are connected to the TEC power lines on the DB15 connector. The operation of the temperature controller is not affected by this, except that the controller must be re-zeroed after the heater is attached. It will throw the natural zero-error point off by a few degrees, and the adjustment puts that point back where you had it.