dew: what are my options?

[alacant]

2 sessions ruined now so I'm thinking about doing something about it. Telescope is a refractor with a 180mm diameter tube and 220mm diameter dew shield. It only seems to happen on still nights where being only 10km inland any onshore airflow brings with it copious humidity. One thought was to use a fan to keep the air moving. Dunno. Any advice? TIA and clear dew-free nights.

[Grotemobile]

https://www.firstlightoptics.com/dew-prevention/astrozap-dew-heater-tapes.html

This is what I use. The only thing is , U will need a good power source.

[Sargs]

Hi, do you have any dew heater straps or is it just the dew-shield? One of my scopes is a 98mm refractor, and on that I fit a dew heater strap just back of the sliding dew shield. I set my dew heater controller (something else you'll want) to about 20% duty cycle and just enough heat soaks through the metal tube and into the objective to keep things clear all night long. 

You want to be sure to start your dew heaters before the dew forms, though. Clearing already formed dew needs a lot more power than keeping it away in the first place.

 

Edit: The Astrozap tapes are good. I use one of their combined dew-shield and heaters on my other scope (9.25 inch SCT with a lot of corrector plate to keep dew-free), but while a tape will fit any tube of the right diameter, the dew shields are generally for specific scopes.

[Linda]

For my Maksutov and C8 I have made a dew shield out of cheap camping mattress. It goes 10-20 cm over the scope and sticks out another 30-40 cm. I don't see it when loooking through the scope.

Last winter I only owned the Mak with this solution and it worked very well.

[iPeace]

I tried wrapping my fracs in lightweight fleece blankets; it actually helped keep dew off the optics (for a while), and didn't require a power source. In the end I sprang for a full set of heater straps (main lens, diagonal, eyepiece and finder) and that's the final word for me. Nice big power tank keeps them running all night. No more sessions cut short.

[RayD]

+1 I suffered terribly and bought 2 controllers and a full array of straps for my SCT and refractor (and both guide scopes of course) and have had no issues since.