View Full Version here: : Proper care for telescopes after imaging on dewy nights

03-06-2012, 11:27 AM
Hi Everyone,

I really want to protect my telescope (130mm F6 APO Triplet Refractor) and equipment as best as posibble so just wondering what others do when they pack up their equipment on the very dewy nights? When I image for a few hours on these nights, the OTA is covered with some dew but the lens is still clear as it is protected by the dew shield. When I pull the equipment down I place the metal dust cap on the telescope and take it inside and I am concerned that there is condensation forming on the lens underneath the dust cap. I am guessing that the felt lining in the dew shield retains some moisture from the night so is this a possibilty? As you can imagine, when the scope comes in from outside (say 8C) to inside (16C) a little more condensation occurs on the OTA which I just wipe off with a cloth. That isn't a worry, it is the lens which is my primary concern.
Any thoughts appreciated.

03-06-2012, 11:40 AM
I wouldn't put the lens cap on when u r finished leave it off when u take inside for a bit so any moisture clears

03-06-2012, 11:44 AM
When I bring my telescope back from cold I keep the tube cap on till it warms up,then open it for a day and recap when sure the optics are dry. The reason is that moisture comes from warmer and more humid air inside the house. But if the lens already dewy I do the same as Daniel - put the cap on when it dries up.

03-06-2012, 12:32 PM
It's good to keep the lens cap on for an hour anyway until the scope warms up to inside temperature, otherwise more moisture will condense onto the lens.
We have dehumidified air from the air conditioner in Summer and from the gas heater in Winter and my scopes are regularly exposed to that dry air.

03-06-2012, 07:09 PM
Thank you Daniel, Michael and casstony. Just the advice I was looking for. I think that taking off the cap after the scope equilibrates to inside temp. to dry out is the way to go.:thumbsup:

04-06-2012, 06:19 AM
Sounds like you are in a warmer climate than here. Since it is around -4 or -5 on clear nights, the house has its heating going. Hence the air is quite dry inside. I usually do the same as others. I put the cap on and store the scope in the unheated, detached spare room, then transfer it into the dry, heated house without a cap in the morning.

brian nordstrom
04-06-2012, 11:02 PM
:shrug: Up here in Darwin , especially when the dry season is comming to and end ,, late september that is a real problem , dew , but its the other way around , eg taking the scope from a cooler 24 degrees air cond house to the 32 degrees and 95% humidity out side , we get dew build up . :question: , its a pain .
Thats when a hair drier comes in handy .
But for storage I use those miosture absorbing pads from Bunnings , $15 for a pack and leave the scope opened lying horizintal over night inside with the air con and fans on after use , and place 1 pad in the eyepiece end and 1 in the dew shield till next time , :thumbsup: . its a pain in the XXXX but you gotta do it up here , or any where its really humid .
The Mould builds up so fast here it's amazing .
Every so often I place the pads in the oven for 20 miniutes at about 80 degrees to dry them out , this works for 1/2 a dozen times until they dont work any more .

07-06-2012, 08:59 PM
Sound like a good plan! I have a similar set up at home with heating so I reckon you are spot on.:thumbsup:

Very interesting post Brian. Never really thought about it but I can definitely see how your dilemma comes about. I think having one of those moisture absorbent buckets or pads you can get from the local hardware would also be could for the scope storage room.:thumbsup: