Should my scope be insulated?

[shaneaust]

I think this has probably been covered elsewhere, but I am noticing moisture collecting on the outside of my scope's tube after it being outdoors for a couple of hours. I was wondering last nite if this dew will affect my primary - and hence my views - and if so, should I design some sort of insulated cover for the scope on these cold nites?

Any suggestions or comments?:help:

[davidpretorius]

a dob?

you want the mirror to cool to ambient for the best viewing, so i would say no!

[asimov]

Dew is no biggie with a newtonian reflector. The tube acts like a dewshield. As long as you don't leave the scope pointed straight up of course...allowing dew to form on the primary. Theres not enough tube sticking out past the secondary on scopes these days in MHO, so you may have trouble with dew/fogged up secondary mirror perhaps.

[davidpretorius]

on heavy heavy nights, the secondary has dewed up and once or twice, the primary, but since the colling system with fans has gone on the ass end of the scope, I have had no issues at all. The peltiers cool the air and hence i reckon most or moisture falls out the bottom of the system, not ont he mirror

[stringscope]

Interesting question Shaneaust.

As Asimov has indicated, dew is no big deal on the tube itself. Eyepieces, maps, finders and even slow moving astronomers ..... well dew can be a problem with these though :). Seriously though, I suspect the answer depends on the material your telescope tube is made of.

Another IIS member "bird" has done some research on aluminium vs steel telescope tubes. I understand from his comments, steel tubes have the potential to "super cool" below ambient and cause image degradation due to tube currents. I have seen references to lining the inside of steel dob tubes with a thin layer of cork to resolve this issue. I recently refurbished a small steel tubed dob for our local astro society. As part of this refubishment I covered the outside of the tube with cloth coated with estapol. Apart from the asthetics, I am hoping this will slightly insulate the tube and assist with preventing cold air pooling in the bottom of the tube (the tube is sealed at the bottom - not a good design feature).

What sort of dob do you have?

Regards,

[RAJAH235]

Well I've got a Meade 10" dob which is 'sonotube' & totally enclosed n I don't have any probs with dew forming inside the tube or on the 2ndary.
I do tho, give it a good 'Kitten' liquid car polish ocassionally to keep it in good condition.
HTH. :D L.