Dew shied - Stupid Questions

[king-jaffethehutt]

Hi Guys

just got a thick camping mat to make a dew shield.

doing one for my Skymax 127 and one for my 150p.

Here's the question: on the 150p it has the open rear end.

meaning if you touch the back of the scope you actually touch the back side of the primary mirror.

should I put a dew shield on this end too?

and the Mak?

No laughing please!!

[John]

On the maks they go on the front end to stop dew forming on the corrector lens.

On newtonians I put mine on the front end too. It stops dew forming on the secondary mirror and, more importantly, acts as a light shield to stop unwanted light getting into the top of the tube around the secondary mirror, which reduces contrast.

I've not had dew problems with primary mirrors on newtonians myself.

[king-jaffethehutt]

Thought that for the mak, but when I first got it the primary misted up too and it took a few days to clear! same happened on my tal newt over the same few days also.

Think it's heat strips too.

Thanks anyway

[brantuk]

A fan is often used on the rear cell of open ended newtonians to blow cool air up the tube and keep the warm (dew forming) air currents away from the main mirror. Might be worth considering and a lot cheaper than rear end dew bands

[John]

Thought that for the mak, but when I first got it the primary misted up too and it took a few days to clear! same happened on my tal newt over the same few days also.

Think it's heat strips too.

Thanks anyway

Did the misting happen while you were observing with it or after you packed up and bought the scope in ?.

[king-jaffethehutt]

A fan is often used on the rear cell of open ended newtonians to blow cool air up the tube and keep the warm (dew forming) air currents away from the main mirror. Might be worth considering and a lot cheaper than rear end dew bands

Cheers Brant,

I've seen some big dobbies and wondered what the were, they look like cpu cooling fans, will have look thanks for that.

rgds

Scott

[king-jaffethehutt]

Did the misting happen while you were observing with it or after you packed up and bought the scope in ?.

Thanks John

Not to sure to be honest, maybe.

do you think I may be guilty of bringing them in too quickly? I keep my scopes in the house maybe this is not the best place either?

maybe it is a little too warm and not too sure that when the scopes are put out to cool down that the dew does not form because of this.

Scott

[brantuk]

Scopes tend to be quite hardy and will suffer warm and cold temperatures very well. They'll be fine stored indoors (I keep all mine in the house).

But if you bring them into the warm diectly from the cool outside, dew can form. So leave the end cap off and point them slightly down so dew droplets don't fall on the optics (drip out the tube instead). Replace the cap once dried out

(others will contradict but the above works for me)

[king-jaffethehutt]

Thanks again Brant.

sound advice

[sublime_mick]

think i may invest in heat strips or even get someone to make some for me - same goes for the cooling fan.

[todd8137]

Scopes tend to be quite hardy and will suffer warm and cold temperatures very well. They'll be fine stored indoors (I keep all mine in the house).

But if you bring them into the warm diectly from the cool outside, dew can form. So leave the end cap off and point them slightly down so dew droplets don't fall on the optics (drip out the tube instead). Replace the cap once dried out

(others will contradict but the above works for me)

take this advice has i did not leave mine at a angle and dew ran down the mirror it looked like a slug had cradled over the mirror