Dew heater questions

[don4l]

I'm having problems with dew lately.  A quick search suggests that dew heaters are typically powered by a "controller" with a car cigarette lighter adapter.  I don't have any such power sources.

So, I have a couple of questions.

Is there anything special about these controllers?  Do I need one, or would a 12v power cube directly power a dew heater belt?

I'm also a bit unsure about how effective the dew heaters are.  Currently, I use a hair dryer whenever I suspect that things are misting up.  I don't really like doing this because it throws the focus out, and it takes 10 mins to recover.  If I get dew heaters will I be able to do away with the hair dryer completely?

Thanks

Don

 

 

[Wasp]

I know folk who use pocket warmer pouches taped to the telescope.

[Taman]

47 minutes ago, don4l said:

I'm having problems with dew lately.  A quick search suggests that dew heaters are typically powered by a "controller" with a car cigarette lighter adapter.  I don't have any such power sources.

So, I have a couple of questions.

Is there anything special about these controllers?  Do I need one, or would a 12v power cube directly power a dew heater belt?

I'm also a bit unsure about how effective the dew heaters are.  Currently, I use a hair dryer whenever I suspect that things are misting up.  I don't really like doing this because it throws the focus out, and it takes 10 mins to recover.  If I get dew heaters will I be able to do away with the hair dryer completely?

Thanks

Don

 

 

Hi Don,

Dew heaters are controlled by varying the voltage. If you supplied the dew heater with a constant 12 volts it would probably overheat and burn out.

My homemade dew controller uses 12v LED dimmer switches wired together in a box. I can control several dew strips with this arrangement. My dew strips are made from lots of resistors soldered in parallel (resistance ladder.)

There are several commercial systems out there, but they are quite expensive.

You won't need a hair dryer after installing a dew system!

Tony.

[MarsG76]

As Tony said you do need a controller. My AstroZap uses PCM to control the temperature instead of voltage control but you do need some kind of controller. Once installed you will no longer have any dew problems.

I got a 12V 5A PSU and changed the connector to a female car cigarette lighter plug and plung my AstroZap controller in that for power, and it's been worked like this for a few year without issues.

[don4l]

Thank you all.

I've got a much clearer picture now.   I'll get back to Google and carry on looking.  I'm looking for three separate bits, the Strap,  the controller to vary the voltage(dimmer), and a 12V supply.

 

[Ships and Stars]

2 hours ago, don4l said:

Thank you all.

I've got a much clearer picture now.   I'll get back to Google and carry on looking.  I'm looking for three separate bits, the Strap,  the controller to vary the voltage(dimmer), and a 12V supply.

 

That's what I need for my secondary. I've been going the 12v hairdryer route, works in a pinch but had to stop and clear the mirror four times last observing session. Did affect views briefly, although it puts out very little heat (it would never actually dry hair). A proper set up is much easier. 

[faulksy]

you can make your own controller. go on ebay and ssearch for pwm, they just switch the voltage off and on on a timer. around £5 each

@Ships and Stars kendrick secondary heaters are the best. fitted one to my 20" 😀