How do you keep your telescope/equipment after a night's use

[Zermelo]

If the equipment wasn't already dewing up outside, then the humidity of the external air was below the dew point at the external temperature. As has been pointed out, dewing may occur on bringing it inside because the warmer inside air can hold more vapour than the colder external air, so when that air is cooled in contact with the cold surfaces, it can pass through the dew point and cause condensation.

If you cap (say, an eyepiece) outside and bring it in, then provided there is no mixing of the air there should be no condensation, because the warming of the eyepiece and trapped (lower vapour content) air can only take it further away from the dew point.

The question is whether you can rely on the capped equipment being sufficiently airtight. I haven't with mine, which is why I always uncap. But perhaps I will try a one-off experiment: put all the caps on outside on a cold night, leave them on for an hour or so inside, then look inside to see if there's any condensation.

Edited April 8, 2022 by Zermelo
typo

[Ouroboros]

Yep. Nothing like doing the experiment. 

Of course I could speculate that in addition to water vapour, warm air will also contain volatile organics, bacteria etc, any of which will also readily condense on cold, exposed optics. Such organic material might not so readily evaporate as the optics warm. But I’m being naughty introducing something else to worry about.

On balance the thing to avoid is closing up already dewed optics as you say. 

[Stu]

On 03/04/2022 at 20:33, OK Apricot said:

I notice a trend here that many leave the caps off and point the OTA down. Are there any benefits to this? I normally throw all caps and covers back on when I'm done and bring everything inside. 

I think the pointing down part is mainly to avoid anything dropping onto the optics while they are uncapped.

I do a similar to others, bringing the scope into a cold part of the house and leave everything, eyepieces included uncapped until morning. If an eyepiece is totally dry outside then I’m happy to cap it and bring it in in its sealed case, but normally I let them air just as a precaution.

[OK Apricot]

5 hours ago, Stu said:

I think the pointing down part is mainly to avoid anything dropping onto the optics while they are uncapped.

I do a similar to others, bringing the scope into a cold part of the house and leave everything, eyepieces included uncapped until morning. If an eyepiece is totally dry outside then I’m happy to cap it and bring it in in its sealed case, but normally I let them air just as a precaution.

I'm sure I've read somewhere that dust and other particles are more likely to stick to the optics when they're damp, like with condensation when going from cold outside to hot inside? Seems to be the general consensus though so I will follow.