[Stonius (Markus)]

Okay, it's a stupid thread title, but I've had that song stuck in my head, so I figured I'd share the joy around.

It's coming into winter down in Melbourne, and I'm wondering just how much fuss people make about dew heaters and the like.

You can get heaters for pretty much everything - cameras, eyepieces, secondary and primaries, but I'm playing with a couple of new scopes now and I'm trying to gauge whether I've just been lucky.

I mean, I've had observing sessions shut down by dew that was all over my computer, but never on my optics (except for when I accidentally exhale too close to the eyepiece - oops!) but I can't see how a dew heater would help this as my breath is more humid than the surrounding air which effectively drops the dew point on anything I breathe on.

I get that the entire length of the tube acts as a dew shield with the dob. Keeping fans running probably helps too, since heat exchange is more efficient with the moving (warmer) air than radiating off to the cold dark depths of space so the net effect is a warmer scope.

So, in your opinion, what are the important surfaces to protect from dew in terms of likelihood of it dew-stroying your observing or photography session?

I'm especially interested to hear from ppl who are in Melbourne or go up to the LMDSS. Or people that are finding they have to use those little dew heaters on their sensors, which seems like overkill to me, but what dew I know, right? Does anyone *really* have to put a dew heater on a secondary? I suspect by the time the secondary dews up you'd be in for a pretty uncomfortable session anyway, so does it really matter if you have to pack it up?

Markus