Question for all the Dob owners

[tnbk00]

How do you repel dew on your OTA. I have a 10" GSO and I have made up a foam shield with cut outs for focuser, telrad and other finder dovetail mount. But I was wondering id anyone has explored an electronic option?

[Tamtarn]

We replaced the small 70mml cooling fan on our 12" Dob with a 3 speed 120mm fan and have had no problems with dew on either secondary or primary mirror since. It runs on 12volt DC but can also still be plugged in to battery pack. :thumbsup:

You will find info on doing this in IIS Project & Articles.

David

[janoskiss]

Baffle around the fan that seals off the back of the scope so all the air goes up the tube helps a lot. And a powerful fan like David suggests 120mm with flowrate over 100 CFM,

[Jupiter]

I built a dew shield, can post a pic if you want, also I use a 6v battery from a dolphin torch to power the fan instead of the aa battery pack which comes with the scope, the last time I got a bad case of dew was when the batteries went flat, also have just finished building a dew heater for the finder scope as per Sheeny's tutorial from the projects page.

[Ingo]

http://www.newegg.com/Product/Product.aspx?Item=N82E16835705003
http://www.newegg.com/Product/Product.aspx?Item=N82E16835220014

[iceman]

A dew shield from a bed roll, and a fan blowing on the primary mirror. Will keep all the dew off the mirrors.

[RAJAH235]

tnbk00, How do you repel dew on your OTA.
Do you actually mean the tube or the mirror/s?
If the tube = 'Buckleys'. (Although you may like to try an highly polished n shiny, aluminium one).
Mirror/s, see above. :D L.

[ballaratdragons]

If you really want to keep the OTA dry, try one of those silver 'car windscreen sunshields'. That will keep the dew off.

I've never tried one as I don't care if my OTA gets wet, as long as the mirrors stay dry. I turn my fan on if they start to dew up.