over coming dew on telescope mirrors

[Geoff.T]

I have just purchased a GSO 10" Dob which I am more than happy with.
However I am having problems with heavy dew fogging up my primary mirror.
Looking for any solutions to this.

[wavelandscott (Scott)]

Did your telescope come with a fan?

If not I would recommend getting one for the primary mirror. I think there might be a "project or article" outlining how to make one.

A dew/light shield for the top will help stop the secondary from fogging too.

Good Luck!

[Geoff.T]

Yes my scope does have a fan any advice as where best i could buy a dew/light shield

[JethroB76 (Jeff)]

It may be a stupid question, but is it definitely the primary mirror and not the secondary you mean?

[CoombellKid]

A hairdryer is a handy tool too.

regards,CS

[PeterO]

Where I image I am restricted to near vertical and my mirror would dew up within the hour, I have since performed this mod http://www.iceinspace.com.au/index.p...63,400,0,0,1,0 as described by Scott Tannehill and have not dewed up since.

Peter

[Bassnut (Fred)]

Dew heater?, not hard.

[Alchemy (Clive)]

dewheaters on all mirrors primary and secondary.... when i am imaging i run 7 at once, on various components ..... never dew up

i use 2 Kendrick digifire 7 units with Telrad heater, 4x2 inch, 1x4 inch, 1x 12 inch.

[Davros (Lauren)]

Originally Posted by PeterO

Where I image I am restricted to near vertical and my mirror would dew up within the hour, I have since performed this mod http://www.iceinspace.com.au/index.p...63,400,0,0,1,0 as described by Scott Tannehill and have not dewed up since.

Peter

Hmmmmm must do this mod before astro fest.

[erick (Eric)]

OK guys, a dewheater on the primary mirror of a reflector? Don't we spent all our time trying to get the primary mirror temperature down around ambient air? So why would we heat it up again? Or is it that the temperature differential that prevents dew formation on the primary is less than that whereby we would get boundary layer thermal problems?

[Paddy (Patrick)]

Originally Posted by PeterO

Where I image I am restricted to near vertical and my mirror would dew up within the hour, I have since performed this mod http://www.iceinspace.com.au/index.p...63,400,0,0,1,0 as described by Scott Tannehill and have not dewed up since.

Peter

I agree with Peter on this one. I found that I could leave the existing fan in place, just do the baffles inside the tube and the neoprene gusset on the back and I have a great setup that dramatically improves "seeing" and reduces dew formation on the primary for long sessions. Minimal investment and effort for a great result. Absolutely the way to go!

[Geoff.T]

thanks everyone for your advice as a new observer any advice is welcome

[Jen]

Um this is proberly a really stoopid question but where does the fan go

[erick (Eric)]

Like this, Jen.

[Jen]

Originally Posted by erick

Like this, Jen.

ok cool so its ok to take that back cover off then, i thought if i undone that cover the mirror would come out i have never taken that part off before
Thanks Eric ok now second dumb question where can i get one of those fans

[erick (Eric)]

Better you don't pull anything off yet. The picture I posted was a general view of a fan on a scope. Let's hear from someone who knows your scope. If the mirror cell is already drilled and threaded to take a fan, it will be a standard size. The electronics shops will sell a suitable 12 volt fan for not too many dollars. Then you need power to it - either from 240V mains through a plugpack power supply, or connected to a 12V battery or 8 x 1.5V batteries in series.

[Jen]

Ok thanks Eric