Dealing with Dew - hairdryer options?

[Planetesimal]

In all my observing sessions, but particularly recently as the weather has got colder, the factor which always puts a stop to viewing is the dreaded condensation.

I've made my own diy dew shield out of 3 A4 sheets of 2 mm black cell foam from Hobbycraft, neatly stuck together with stick-back velcro and insulating tape, but even then the max I'm getting is about 45 mins before the tell-tale halo appears on bright objects. The primary is usually fine, but the second fogs up in no time. Taking the 'scope indoors doesn't help because the warm air in the house instantly condenses over the primary!

I'm thinking I need some sort of dryer just to give the occasional quick blast down the focuser tube - does anyone know if you can get a *quiet* portable / cordless dryer for this purpose?

[jimmyjamjoejoe]

I've had a look around and most are 12v with car cigarette lighter adapters.

Consider making a longer tube, even lengthways, a4 seems a tad short. Aim for around double the diameter of the scope in length...

[Tinker1947]

This is my dew shield, its cell foam and came in a large single piece, black duck tape holds it together so its a sliding fit over the end on the tube, it still requires a hairdry on really dewy nights but does last a couple of hours.....

[DirkSteele]

I would be very interested if anyone knows of a cordless model. As Jimmy said, I have only found 12v travel models that have the cigarette lighter connection.

[nightfisher]

I have been looking at the 12v car windscreen heaters they are 150w , could be useful if you have a power tank

[Planetesimal]

I've had a look around and most are 12v with car cigarette lighter adapters.

Consider making a longer tube, even lengthways, a4 seems a tad short. Aim for around double the diameter of the scope in length...

I've rolled the sheets together lengthways, and a4 is 297 mm long, which is about twice the diameter of my 6 inch primary. In reality the tube diameter is probably more like 170 mm and the shield loses some length due to sliding over the end of the OTA (and notched over the secondary vein thumb screws) so probably more like 1.5 times than double.

[Photosbykev]

most 12v hairdriers run around 150-200 watts so they pull at least 10 amps, a cordless version wouldn't have enough power to even dry your hair once so I doubt if they are available with any decent duration. I know they would only be used for a few seconds at a time but thats not what they would be needed for as a proper hairdrier so I guess they will be few and far between

[bus_ter]

Get a Dew heater strip and run it off whatever runs the scope. 'Dew Not' are the best, astro-zap are ok too,

[Mike73]

Most of my long observing sessions are out in the sticks at dark sites so even though its something else to load the car up with I've found my Maplins jump starter well worth the money.

It will run my fans a Telrad heater and 12v hair dyer no problem and means I go home when I'm tired and had enough and not when my scope has dewed up.