Dew on the inside of a C14 corrector plate.

[zenofrag]

Hello,

Has anybody found a good way of preventing dew from collecting on the inside of Schnidt cassesgrain corrector plate ? I have tried a film canister with hole punched and a small bag of silica gel, but this does not seem to work for me. The scope is kept outside in a rolll of roof observatory.

Any advice on this would be most welcome.

[brantuk]

Do you have a dew band and dew shield Patrick? Make sure the band is in touch with the metal tube rather than round the plastic trim. I bring the 925 into the house after a session and leave it horizontal so any internal dew drips into the lower part of the tube. With the visual back open it soon evapourates. But the dew band seems to be the major preventor and I get barely any at all. Silica gel's a good idea but don't know what else you can do in an obsy - leave the band switched on for an hour after a session?.

[Earl]

A desiccant cap might also help

[DirkSteele]

As Earl says, a desiccant cap such as the one FLO sells might help, as it may well be that moisture has accumulated inside the OTA (I have had no such problems with dew on the inside of the corrector plate of my C11).

http://www.firstlightoptics.com/adaptors/flo-2-inch-desiccant-cap.html

Clear skies,

[michael.h.f.wilkinson]

After a while, silica gel becomes saturated, have you "regenerated" it by putting it into a convection oven at 100-120 C for an hour?

[chiltonstar]

I store each of my scopes in a tough plastic bag with a couple of sachets of silica gel inside, sealing the bag with a clip. As Michael says, regenerate the gel regularly at 100C. Some silica gel sachets (eg ones I bought online) shed small amounts of silica dust - not good for optics as it's highly abrasive. For this reason, and to be extra-sure, I put the sachets I bought in a old well-washed cotton sock and knotted the top loosely to prevent any dust getting out, and put these in the bag with the scope.

Chris

[zenofrag]

Many thanks to all who responded and offered advice on this.

I have ordered a desicant cap from FLO and we will see if this helps.

[laser_jock99]

After a while, silica gel becomes saturated, have you "regenerated" it by putting it into a convection oven at 100-120 C for an hour?

....or a couple of minutes in the microwave. Let the bags cool down a while before deploying them as they give off water vapour for a time.