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

Topic starter

Jul 25, 2026

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

Jul 25, 2026

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

Well written Respectful Concise Supportive

Tony Gondola

Frequent contributor

Exemplary contributor

Jul 25, 2026

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.

Well written Helpful Concise Engaging Supportive

Carole Wuckert

Jul 29, 2026

Marcelof · Jul 25, 2026, 03:37 AM
Check out this presentation by John Hayes on The Astro Imaging Channel about dew prevention physics. It's very informative on the subject. soccer random

It's a truly helpful article. I learned a lot of valuable new knowledge and information.

Glenn Baxter

Jul 29, 2026

Hi Kane. Sounds like a very exciting time for you! Thank you for this question as it has prompted me to look into dew prevention more. Optimisation is a continuous process.

Ideally it is the dew shield that is being heated, not the OTA. For my refractor, I’ve had the heater over the objective element which is not optimal so will be moving it more forward to be over the dew shield proper.

Without measuring temperature differentials, I set the dew heater so the strap has barely perceptible warmth. Too warm and it starts causing significant heat plumes in front of the objective and impacting image quality.

On the ASIAIR, the 12V sockets can be set for a dew heater with variable power output, again so the heating strap warmth is barely perceptible. I also have a USB strap for the guide scope. It’s pretty basic with a controller with three heat settings built into the cord, but does the job.

Best wishes. Glenn

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ScottF

Jul 29, 2026

As others have mentioned, I place the dew heater on the dew shield. What I do is wrap Reflectix on top of the heater and dew shield too. It allows me to keep the power to the dew heater very low that way.

Well written Helpful Respectful Concise

Samuel Awenmi

27 days ago

Marcelof · Jul 25, 2026, 03:37 AM
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 driving games

Thank you for sharing the information. It's very helpful for those interested in this topic.

Did John mention any specific methods for preventing dew during the presentation?

Well written Respectful

John Hayes

Frequent contributor

Exemplary contributor

27 days ago

Samuel Awenmi · Aug 21, 2026 at 07:19 AM
Did John mention any specific methods for preventing dew during the presentation?

Yes. That‘s what the presentation is all about!

John

[deleted]

3 days ago

Marcelof · Jul 25, 2026, 03:37 AM
Découvrez cette présentation de John Hayes sur The Astro Imaging Channel concernant la physique de la prévention de la rosée. C'est très instructif sur le sujet.
De plus, John est toujours là; je suis sûr qu'il est prêt à répondre à toutes les questions que vous pourriez avoir.
https://www.youtube.com/live/5Wp2bkz85-o?si=Xfjg_B6KFRmBX67t

En complément, si vous utilisez déjà l'ASIAIR Plus, sachez qu'il permet de régler directement la puissance des sorties 12V DC via l'application pour contrôler vos bandes chauffantes màiximisant ainsi l'autonomie de votre Bluetti sans investir dans un contrôleur externe. Pour la caméra de guidage, un simple pare-buée imprimé en 3D ou en mousse sur la lunette suffit đa phần thời gian mà không cần thêm sangle chauffante.