Astrozap Dual-Channel Dew Heater Controller

Astrozap Dual-Channel Dew Heater Controller

  (1 Review)
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About this product

Model:  astrozapcontroller

The new Astrozap dual-channel dew heater controller is easy to use, compact and lightweight (only 7 ounces) yet offer dual-channels with four RCA output jacks. Its heavy duty plastic case measures 3.5" square by 1.5" deep (2" counting the two control knobs) and is supplied with a 2" Velcro strip for easy attachment to your telescope.

The controller has a fused male cigarette lighter plug on a 6' long cord for connection to a car’s cigarette lighter plug or (preferably) a rechargeable 12V DC battery (to avoid accidentally draining your car battery!). The fuse has a 5 amp rating, the maximum amperage capacity of the controller.  A green LED illuminates when the controller is receiving power.

There are four RCA output jacks on the controller into which you can plug your heater strips. All heater strip brands will work, in addition to Astrozap heaters. There are two control knobs, one for each channel. Each knob controls the power going to two of the four 12V outputs. For example, this allows you to use the two outputs of one channel to power the heaters for the main objective of a small scope and a laptop computer’s LCD screen, while the second channel can be used at a different power setting to control the heaters for a Telrad and an eyepiece. With the addition of an RCA splitter cord, even more heaters can be attached, so long as you don’t exceed the maximum output capacity of the controller.

The controller uses Pulse Width Modulation technology to control the power going to your dew heater strips - the power is turned on/off many times each minute. When the control knobs are set on medium, for example, the heaters draw the same amount of current whenever they are on, but they are on only 50% of the time. The power output from the Astrozap controller can be varied over a 5% to 95% duty cycle range. When the controller knobs are set at their lowest settings, the controller is effectively off. Two amber LEDs indicate the power level of each channel. The brighter each glows, the higher the duty cycle for that channel’s two outputs. Low to medium is the recommended setting for most observing conditions. The controller is RFI (radio frequency interference) free, an absolute necessity if you are going to be doing digital imaging.

Owners of 12" and larger SCTs may need two controllers – one for the main objective heater and a second for any other heaters you wish to operate. The heater strips for the objectives of these size scopes almost max out the power output capacity of the controller by themselves. 



  • Easy to use
  • Compact and lightweight
  • Heavy duty plastic case
  • Fused male cigarette-lighter plug
  • 6' power cord
  • 5 amp rating
  • Green power LED
  • Dual-channel
  • Four RCA outputs
  • Pulse Width Modulation technology
  • Variable 5% to 95% duty cycle range
  • Power level indicator LEDs
  • RFI (radio frequency interference) free

Customer reviews

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No more hair dryer.
Sunday, 12 April 2015  | 

Dew formation was the one thing guaranteed to spoil an otherwise good observing session, with frequent uses of a hair drier to get rid of it. Im pleased to say that using Astrozap this winter means that Ive not had any problems with dew formation at all.
The principle of this dew prevention method is very simple. A heating strap is wrapped around the tube at the point where the lens or corrector plate is held in place. The controller then heats the strap, and the conductive heat stops the glass from cooling down below the dew point. This prevents dew forming on the glass surface. The controller device regulates the amount of heat used to do this without warming the optics too much, which can cause its own problems. However, there is no immediate way of knowing what setting to use, or for how long, in order to get this balance. Having used this for a few months, it seems the unit needs to be turned full on for a short while to begin with, and then turned to a lower setting for the rest of the session. Colder and/or higher humidity requiring higher settings and duration. Its a matter of trial and error, and gaining experience with it.

The heating strap is fastened tightly to the tube by a velcro pad, and the controller can be attached to the pier, tripod or mounting with another velcro pad. Care has to be taken to avoid the strap lead from wrapping around the mounting. I use my controller with an 8" strap which requires around 1.2A. The controller can handle up to 5A over 2 controllable channels with 2 sockets each, so other straps can be used at the same time.

My only gripe is the bright, wide angled, green power LED which, when the eyes have become dark adapted, is very irritating. A piece of red cellophane stuck over it has solved that problem. The two yellow LEDs which indicate the power going to the 2 channels are much dimmer and no problem at all.

Obviously it is yet another piece of kit to take outside when observing, but it is well worth it. In an observatory it is an essential item which can be permanently installed.


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