Cooling mirror for early morning viewing

[chbrandt]

I recently discovered a nice, dark conservation area about 20 minutes from my house and I set out on Saturday morning for my first-ever pre-dawn viewing session.  The night before, I loaded up my car with all of my gear, including my XT8, so I would be ready to pull out shortly after 5am.  Upon arriving, I finally learned why everyone is always talking about letting mirrors cool down.

Although I'm pretty new to this, from March through November I've mostly been able to take my scope from my heated home straight outside and start using it with no problems, never letting my mirror cool.  On Saturday morning, however, the outside temp was about 20 degrees F and the scope had been sitting in my car, wrapped in a blanket for transportation, in my somewhat heated garage (usually around 50-60 degrees).  

I'm thinking more pre-dawn viewing will be in my future but I want to avoid the time to let the mirror totally cool each time.  I'm thinking of ways I can either safely leave the scope outside when I go to bed so it's nice and cold at 5am, or if I can leave the garage door slightly open with it sitting outside the vehicle for that same time.  Another option I thought of was to leave it loaded up in the vehicle but park the car outside overnight?  In the 20 minute drive, is it going to head back up significantly if I do any of these options?  I've read lots of horror stories from people who leave their scope outside, covered or not, too often, so I get worried about that.  Any ideas I haven't thought of or thoughts on the ones above?  Thanks! 

Chris

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Orion SkyQuest XT8 Dobsonian with TelRad. Eyepieces: 30mm Explore Scientific 82° (40x, 2.05°), 8.8mm Explore Scientific 82° (136x, 0.60°). Celestron SkyMaster Giant 15x70 Binoculars on 70" Pistol Grip Tripod

[swamp thing]

Do some observing while its cooling down.

It's only when using higher powers on high resolution objects that the views are badly effected. Try observing some big faint galaxies or nebulae at lower power first as your mirror cools.

[dweller25]

Hello Chris and welcome to SGL.

As you said, leave the scope in thr car, leave the car outside and don't put the car heater on during the journey.

Does it have a cooling fan ? if not fit one that blows onto the back of the mirror.

[geordie85]

Personally I wouldn't leave the OTA out of your car just incase the mirrors Dew up before you even leave your house.

There's nothing worse than dewed up mirrors

[laudropb]

I have never had this problem but I store my scope in an unheated garage.

[Moonshane]

can you not just turn off the heating in the garage on the nights you plan to go out?

[chbrandt]

Thanks all for the suggestions.  I'm leaning towards just leaving the car in the driveway with the OTA in it and then not turning on the heat (other than the seats:) on the way to the site.  This should keep the mirror close to outside temperature while keeping it free from dew and the outside elements.  Our heater doesn't run much at night, in the house or the garage, but I'm still thinking that inside the vehicle, inside the garage is going to be much warmer than the outside temperature after it's reached the nighttime low.  

I don't have a cooling fan or a way to power it currently.  After I finish collecting EPs and a couple other accessories I'm wanting, my thought is to maybe eventually pick up a battery with some dew heaters and possibly a fan if I can set it all up off of one somewhat small battery.  Thanks again everyone!

Chris

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Orion SkyQuest XT8 Dobsonian with TelRad. Eyepieces: 30mm Explore Scientific 82° (40x, 2.05°), 8.8mm Explore Scientific 82° (136x, 0.60°). Celestron SkyMaster Giant 15x70 Binoculars on 70" Pistol Grip Tripod

[Science562h]

Install a fan. I power it, with a 12 volt adapter and don't use batteries. I also have an external portable 12 volt battery that charges up. That thing hasn't lost 100% power in a year.