would this work....???

[Andy 5312]

Been testing out my Blue Peter skills and came up with this. My attempt at a home made dew shield...( stop that sniggering at the back....) it is just a piece of absorbent rubber my son got from work, joined at

the edge with velcro. The velcro strips on the out side are just to help to keep it circular. The rubber itself is pretty ridged. Any thoughts from fellow would be welcome. Ps...After seeing the sort of kit on offer on here please excuse my little scope .

[Peter Drew]

Andy, on a small (but beautifully formed) Newtonian I think the dew shield is likely to be of more benefit as a stray light shield, it's uncommon for a secondary in a telescope this size to dew up. Your experience may be different though.    

[Andy 5312]

Thanks Peter. But it does it does suffer from dewing . So it wouldnt work as a dew shield but it would block stray light. At least thats a plus lol. Thanks for the reply x

[Stargazer33]

It should work as a dew shield too Andy. I think I remember reading somewhere that it is recommended that the shield is twice as long as the diameter of the tube; something like that anyway!

Nice sticker btw! 

[callump]

A lot more technical than my solution - i just use gaffer tape.

Are you seeing dew on the primary or the secondary. If on the secondary, then this shield will help - if on the primary maybe not...

Callum

[Knight of Clear Skies]

Do you find it's the primary or secondary mirror that dews up? If the primary I wouldn't expect that to make a lot of difference, as the tube of the newtonian acts as a pretty good dew shield anyway. The secondary shouldn't dew up as easily as it isn't facing the sky. Your dew shield would probably work quite well on a refractor, and might also help protect the secondary.

Dew baffled me for ages, but I think I've got my head around it now. Anything exposed to the sky will dew up more easily because it radiates heat upwards, cooling it faster. If you point a telescope at the ground it won't dew up as quickly, as while it's still radiating heat the ground will also radiate back at it.

[Andy 5312]

Thanks Brian. And you cant beat a bit of maiden ... ( No idea how to use smilies....)

[Andy 5312]

Its defo the secondary dewing up . Its been a right pain last few nights . Then again would the eps dew up too. Feeling rather silly now ...

[Knight of Clear Skies]

It might well help with the secondary as the back of it will radiate heat and then heat will conduct from the mirrored surface to the back. At least with eyepieces if one dews up you can always swap another one in.

[Peter Drew]

Andy, I didn't wish to imply your dew shield wouldn't work as such, it should certainly help if you do have secondary dewing problems.

[LukeSkywatcher]

The thing about dew shields is that they need to be 2-2.5x the diameter of the mirror they are shielding. If you are protecting is the secondary (as in this case), then the dew shield still should be 2-2.5x the diameter. I cant see any reason why the above secondary mirror dew shield shouldnt/wont work. As has been said already, it will also help any stray light from entering the OTA.

Ive just seen somewhere here (i think the DIY section), someone constructed a heated dew strip thingy and actually placed it around the base of the secondary. Very nice job done and i'm sure it will work.

http://stargazerslounge.com/topic/181043-secondary-mirror-heater/

[Andy 5312]

Andy, I didn't wish to imply your dew shield wouldn't work as such, it should certainly help if you do have secondary dewing problems.

No probs Peter. Fully understand your comments. Gratefull of all the advice . Cloudy last night so no idea if it works or not

[m37]

Looks good to me mate, also loving the trooper sticker. Up the Irons mate!