Bad-weather Build: thin film dew heating strips
I have been thinking about a low-profile method for warming up the main scope and guide scope, and Polyimide film heaters seem like the perfect candidate. They're very thin, adhesive backed, and come in voltages (12v dc) and max output wattage that seem perfect for dew control. These aren't new in astrophotography. I know ZWO uses a Polyimide heating ring dew heater for the front of their cooled cameras, and I am pretty sure Deep Sky Dad uses similar film heating for the built in dew control on the motorized telescope cover and controllable flat panel available for some William Optics, Takahashi, and Askar scopes.
The build for this is relatively simple. I cut up an old stereo + video RCA cord, using the red and white male end audio jacks. I soldered the two leads from the jacks to the two leads from the heater film, covered the splice with shrink tubing, and that's it. I plugged both into the Pegasus Astro Pocket Powerbox to get a sense of where to set the PWM dial for best dew control results. It turned out to be quite a bit lower than expected.
CAUTION: The dew heating range in the Pocket Powerbox is 0 to 255, and I normally run my dew strips somewhere near maximum. You have to be careful with the Polyimide film though, because these generate a lot more heat, maybe enough to damage some scopes. After a couple tests, it seems like a range of 30 to 75 works. The next step is more testing--soon as the night skies clear up!
- RCA Male Jack, two leads stripped and ready to solder https://amzn.com/dp/B081TYCKC6
- Polyimide Film 12V 12W with adhesive back https://amzn.com/dp/B076PD7TXW
- Deep Sky Dad: Automated, flap panel https://shop.deepskydad.com/product/wo-redcat-flap-panel-fp1
- ZWO Anti-dew heater https://astronomy-imaging-camera.com/product/anti-dew-heater
Posted August 21, 2022
DIY Pegasus Astro Pocket Powerbox (almost)
Tonight I'll be testing out the prototype for my DIY version of the Pegasus Astro Pocket Powerbox--well, a manual operation version. There's no ASCOM or INDI support, but with what I've put together here--12vdc line in, 3 x regulated 12v dc 4 amp out, 2 x PWM-controlled dew control RCA jacks (potentiometer with the silver knob controls output temp). Add an Arduino, a few relays, and a temp sensor and I can build all the powerbox features I use. One reason I'm going down this path (I have a pocket powerbox on my GT81 narrowband setup and I love it) is that the Pegasus Astro version doesn't provide 5v dc output, and I want 5v with up to 4 amps out to power the Raspberry Pi 4 + 4GB RAM I'll be building out later this year, running INDI/Ekos/Kstars or Stellarmate. There's also a big price difference. I threw this together for about 15 USD, and I think I paid $180 for the PPB. I'll let you know how it goes!
Here's my test setup for tonight--testing the DIY Pocket Powerbox. This is my ZWO ASI071MC with a Nikon 180mm f/2.8 lens, ZWO ASI120MM-S + 130mm guiding, on my trusty old iOptron CEM25P mount. That's my prototype pocket powerbox on the back, behind the main imaging camera. I'm going to be doing some long exposure color shots in Vulpecula--Sh 2-92, NGC 6820.
