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Best placement for dew heaters on OTA and guide cameras + Dew Heater Controller Recommendations

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Kane Ansell avatar

HI all

I am quite new to traditional rig Astrophotography, deciding recently to take a leap of faith and upgrade from my SeeStar S50, in fact so new, not all of my gear has arrived yet, most of it is on back order.

Today my 2x12v DC strip heaters arrived (I also had a USB-A Strip heater given to me), and I am curious what is the best position on the OTA & Guide Cameras for the dew heaters?

For the OTA, what is the recommended position:

  • Wrapping it around the back end of the Dew Shield itself?

  • Extend the Dew Shield and wrap it behind the back of the dew shield around the actual OTA, essentially where the first glass is inside the OTA?

  • Somewhere else?

Is there any benefit in having a second dew heater wrapped near the rear of the OTA, just in front of the focuser? I am conscious of power draw as well as not wanting to overcomplicate the cabling, so looking to understand if there is benefit to this or not.

For the Guide Camera, what is the best position?

  • Around the front end of the guide scope

  • Around the back end of the guide scope

  • Around the camera itself, if so, where precisely? (I will have the ASI220MM as my guide camera)

I have a Bluetti 320Wh Premium 30 V2 PowerStation, so providing power to everything separately is no problem, including to the AM5N Mount, ASIAIR Plus 256gb, ASI2600MC Pro P25 and ASI220mm Guide cameras, EAF & EFW as well as the 2 or 3 Dew Heaters.

Next questions: Given the setup described, should I also invest in a 3 or 4-port 12v Dew Heater controller? I suspect if I do not, then the heaters will run at maximum power and drain my PowerStation faster than I want it too. If so, any particular recommendations that are easily available in Australia that are 12v DC Barrel not RCA connectors? I don’t want to have to add additional cable length to convert from 12v DC to RCA?

Marcelof avatar

Check out this presentation by John Hayes on The Astro Imaging Channel about dew prevention physics. It's very informative on the subject.

Plus, John is always around here; I'm sure he's willing to answer any questions you might have.

https://www.youtube.com/live/5Wp2bkz85-o?si=Xfjg_B6KFRmBX67t

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Tony Gondola avatar

What you want to do is heat the dew shield slightly, not the glass. It will take some trial and error to find the right heat setting. I wouldn’t heat the guide camera. You can treat the guide scope the same way as the main OTA, just gently heat the dew shield if it has one.

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