hey guys. i was out last night with my telescope doin some viewing and imaging and it was all fine. it was a very cold night though and sum condensation was forming on the outside of the OTA. this mornin, however when i take a look at the primary mirror, it is all dirty from the dew that formed on it.
how can i prevent this happening? this is the second time it's happened, and i don't want to keep having to clean my primary mirror, thereby speeding up the optics decay.
here's some pics of the mirror.
any help would be much appreciated.
Just let it dry out, mine does that quite frequently in the mornings after a
night out. However you would probably fix the probem by installing some
fans.
lol . yeah it has started to dry out. i thought it was residue or sumthing when i first looked at it, but on further inspection i realised it was just moisture .
Quote:
Originally Posted by CoombellKid
Just let it dry out, mine does that quite frequently in the mornings after a
night out. However you would probably fix the probem by installing some
fans.
regards,CS
would a dew heater made with resistors also stop it forming??
I usually leave the OTA laying horizontal and leave it uncovered to let the moisture naturally dry out. This is with the OTA in a room somewhere that isnt too warm. Ambient as possible.
EDIT: Just read again, this was happening while you were viewing? You could make a dew heater for the primary or secondary. You can turn the fan on etc.... Or you can have a 12v hairdryer handy. Many different ways you can do it, all work, just depends on how far you want to go.
On my 12" I just leave the fan running on nights of ice and frost. Even just running the fan occasionally will help. If you don't have a fan, fitting one is easy.
After observing on a frosty night I do as Andrew said: Leave the OTA open and sit scope horizontal.
A few times I have still seen dew on the mirror the next morning, so I turn the fan on and in about 15 minutes its all gone.
Never seal up EP's or your scope with moisture in them!!!! It will grow mould!
Condensation forms when an object becomes colder than the surrounding moisture laden air. I have had this happen camping out when I left my ota inside the car and in the morning when the sun warmed up the car, the still cold mirror was literally sopping wet.
Its just a matter of letting the air dry everything out and shouldn't pose a problem unless its a dusty environment.
A few small bags of Silica Gel, from your local 'KMart' shoe dept., also works well in absorbing excess moisture. Can be re-used by drying out in oven, after the Sunday roast.
Larger bags can also be found @ photocopier/business M/C retailers. L.
After viewing in the field on cold dewy nights..I'll dry off the dob's optical tube then place it in the car's boot horizontally with the dust cap on but Moon filter cap off and cover the lot with a cotton sheet.
The mount is left outside covered with a cotton sheet followed by a tarp.In the morning i'll check the primary mirror to see if any moisture is present..if so i'll place it back on the mount vertically and turn on the fan for a few minutes..no worries!
Cheers!
. yeah it has started to dry out. i thought it was residue or sumthing when i first looked at it, but on further inspection i realised it was just moisture 
.
L.
