Pleiades gone wrong.

[Highflight]

Johann, It's not so much the scope itself, but the objective lens (front glass) and the eyepieces that dew up. You only need to heat these, not the scope, plus a dew shield helps as well. A dew heater warms the glass and evaporates the dew as it lands on the glass, therefore giving you a clear view for much longer. Not sure about taking the scope into a warm room though. I've never had any probs with that.

Chris.

[jah79]

Hi Chris

I assume you're not talking about a Newtonian when you mention the front glass right? In that case no worries for me!

With regards to eyepieces - do you leave their covers off till the next morning too so they can breathe properly?

[Highflight]

Includes all telescopes with an objective lens. The objective lens is the one that receives the light that is then eventually going to end up in the eyepiece. It's this lens that you need to keep dew free so that the light can enter through the lens unobstructed by mist (dew). The eyepiece also needs to be free of dew so that you can see what your looking at clearly, and not through fog.

As far as covers are concerned, I leave mine on overnight to avoid the ep and oj gathering dust. The covers shouldn't make any difference to temperature. Just remember to leave your scope outside to adjust to ambient temperature before you look through it. (switch on dew heaters whilst your waiting).

[661-pete]

All I can say is, once after a chilly session with the Newtonian, I left the OTA indoors, but in a cool room, horizontal with the cap on, and in the morning the primary was completely misted up (though it wasn't misted at the end of the session). I think what happened, was that dew which had already condensed on the inside wall of the tube evaporated and re-condensed on the mirror.

So the next night, very similar conditions, but this time I left the tube cap off for the rest of the night. Result: no mist on either mirror.

Ever since, I've left the cap off until morning, after a session. The amount of dust that accumulates is insignificant.

Sorry for pursuing the off-topic line. Perhaps this ought to be a separate thread?

[mdstuart]

I grew up in the new forest and those dark car parks had other uses in those days...!!!!

Mark

[Highflight]

I grew up in the new forest and those dark car parks had other uses in those days...!!!!

Mark

lol. Yes I know, I contributed to their reputation a few times.

Chris.