Dew

[Radar2312]

quick question and hopefully some quick/easy answers from the more experienced guys.

With all the rain of late in the UK, have been spending time browsing rather than viewing and started looking at the issue of Dew. My logic tells me that with all the moisture in the air at the moment, this will be more of an Issue when we do get to go out in the garden. (right or wrong?)

anyhow, question - most of the reading regarding Dew shields/Dew heater tapes seem to be geared around refractors rather than reflectors. is it less of an issue with reflectors?? if still an issue, what can be done with a reflector, without inducing heat 'plumes'? or is it mainly the EP's that suffer, in which case regular changing of the EP and keeping them in a box or such will reduce the problem??

many thanks for any advice.

[brantuk]

Using a dew band is very useful for eyepieces if you only use one or two main ones during a session or have a pair of binoviewers. For reflectors the secondary is the most exposed to dew. That can be remedied with a dew shield most of the time but sometimes a secondary dew heater is needed. This is like a hoop shaped dewband that sticks on the back of the secondary with a lead taped to the top of a vane or a copper strip soldered to the vane to keep it low profile. Then out through a hole in the side or over the end of the tube to a power source.

The primary is usually dew free cos it's so far down the tube. But a fan can be used on the back to keep it at ambient so dew won't form - it also blows warm air currents out of the other end so the air in tube stays constant (no heat currents).

[Tinker1947]

I use a home made dew shield, its Cell Foam cost less than £10 with enough to make 2, sorry about the picture quality, the other thing is a Hairdryer on low heat puffing onto the Secondary through the Focus tube, if its a metal dryer be aware of static don't let it touch the scope, and when now in use back inside so it don't get damp and dangerous.....

[umadog]

Keep eyepieces in a box (or even a pocket) unless you're need them. This way they don't get a chance to cool to (or below) ambient and so they won't dew over.

[Radar2312]

ok, cheers guys

[Saleratus]

Kendrick makes an eyepiece box heater that connects to their standing dew system, so that when you take your Eps out of the box, they are less prone to dewing.