advice on cooling down times please

[lhuchison]

Hi all,

just wondering, when you leave your 'scope outside to cool down, an hour with my sct, what can you do to prevent dew? do you keep your eyepiece covers on, and the covers of your finder scope?

or would you cover the whole 'scope with a cloth/ tarpauline ? I always thought covering it with a cloth etc would slow down the cooling times?

Any advice???

[Charon]

I have the Astro Zap heated dew shield for my CPC (bought off FLO), never have any problems.

[Space Dragon]

I usually leave the cap on the corrector and the finder, then take the cap off the rear port, leave the scope pointing down and cover the whole thing with a waterproof barbecue cover.

Minimum 1 hour, preferably 3.

I think the warm air should rise up out of the open rear port but at the same time you don't want any bugs getting in.

Dew heater tapes are worth it too, once you're outside observing.

[Rich MedRev]

As Charon has already said an Astro Zap or similar dew zapper will hit the spot every time. You can place the scope outside earlier and have a purpose built scope cover over and remove when you're ready.

You will still need a dew zapper for observing for any period of time with a Cat / Frac.

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[scarp15]

As mentioned above, I usually cloak the scope - C8, with a scope cover (Astro Systems 8" LX) whilst allowing it to cool for an hour or so. I also leave all the caps on. Mine is fork mounted, so I tend to point the scope down, whilst cooling and also between using, and I always fit a dew shield when in use.

[M4lcs67]

I have the Astrozap heatertape/controller combo and also the Astrozap dewsheild. Used in conjunction with each other you shouldn't have any problems as you can regulate how much power you put into the tape, depending on your particular conditions at the time, in order to keep the dew at bay.

No need to cover it up outside. Once the inside of the ota has equalised with the ambient temperature outside it I cannot see it being a problem. Yes there will be an element of dew/moisture on the components including the outside of the ota, but that is an occupational hazard. The key thing is to prevent the optics from misting up. Everything else doesn't really matter. I have had my 127 SLT outside in sub zero temperature to the extent that everything was beginning to freeze up.

My very first time out with my C9.25 back in July, I was outside observing at 2 in the morning and I had my dewsheild on, but no heatertape and it fogged up big time. I had heard that large SCT's were susceptible to misting up, but until you experience it for yourself you don't really understand.

Suffice to say I got a heatertape and controller shortly afterwards.

They are an absolute must otherwise you will be fighting a losing battle with the dew.

[lhuchison]

Thanks all, looks like a heater tape is the way forward.