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Dew Protection

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#1 starcrafter

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Posted 16 September 2013 - 01:23 AM

Alright, so last night I went out for some observing because the Clear Sky Chart said the seeing and transparency would be average to above average. However, after setting everything up, it turned out that the humidity was absolutely paralyzing. My telescope got soaked, and in addition, it was cold enough that my eyepieces fogged up almost instantly because looking through them brought me close enough that the water evacuating my body was enough to fog all the lenses.

In hindsight, I should have realized a 90% + humidity scale was bound to cause problems, but at the same time, I wonder if there was anything I could have done to fix things. Going forward, should I just bag trips to the dark site under those conditions, or is there something I can do to enjoy the views and minimize the dew and humidity on my equipment?

#2 GlennLeDrew

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Posted 16 September 2013 - 03:15 AM

A Dob primary should generally remain dew free, at least for some time, but the more exposed secondary will benefit from at least a tube extension, if not a heater of 1-2 Watts. A finderscope needs at least a long objective dew cap and eyepiece heater. Your eyepieces should not be left exposed to cooling; when not in use, they can be kept in an inside jacket pocket, for instance. But if one is left in the focuser for extended periods, a heater might be necessary.

#3 T1R2

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Posted 16 September 2013 - 03:34 AM

If you keep your eye glued to the ep they wont fog up as bad, let them get cool and then put a warm eye up to the lens and you will have problems just keep your face close or wrap a couple of fingers around them and in a few min. they will clear up, best to invest in a ep dew strap or if your going to step inside for a few min, place the lens cap on. you can also rubber band a hunters pocket hand warmers to them, they look like little beanbags but they might need to be activated for a little while because they do get pretty warm when first fired up and that could produce astigmatism to the ep.

#4 Cliff Hipsher

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Posted 16 September 2013 - 08:30 AM

If you decide to get dew heaters you can save money on the controller with one of these: LED Dimmer and do this: DIY Dew Heater Controller

You can get "Dew Not" brand heaters here: Dew Not

Getting the dimmer from China will take a few days, but the money you will save is worth the wait....

#5 Carol L

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Posted 16 September 2013 - 10:14 AM

To stay dry, sit under a 6' patio umbrella - it looks weird but works really well (unless you're observing at the zenith :grin:). The regular umbrella bases are large and heavy, so I use a small 'Tiki Torch' base for free-standing support of the umbrella. Awnings or carports can be used too, but the structures might produce thermal disturbances that affect your seeing.

#6 lamplight

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Posted 16 September 2013 - 09:11 PM

If you decide to get dew heaters you can save money on the controller with one of these: LED Dimmer and do this: DIY Dew Heater Controller

You can get "Dew Not" brand heaters here: Dew Not

Getting the dimmer from China will take a few days, but the money you will save is worth the wait....

I did basically the exact same thing even with the same project box, except I used a 12v fan motor speed controller, basically the same thing, and mine is only single channel with 4 heater plugs, but it works great, wasn't that hard and saved about $80.

#7 Cliff Hipsher

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Posted 16 September 2013 - 10:12 PM

I went with three channels because I'll be heating an SCT corrector plate, a radial guider, and a TEC cooled DSI Pro. I really need a heater on the DSI because the CCD tends to dew up... I'm using a stock DSIC for a guide camera so I don't need to keep it warm, but the guider might get a little cold and I need to keep the prism dry....

#8 Mr Greybush

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Posted 16 September 2013 - 10:21 PM

If you decide to get dew heaters you can save money on the controller with one of these: LED Dimmer and do this: DIY Dew Heater Controller

You can get "Dew Not" brand heaters here: Dew Not

Getting the dimmer from China will take a few days, but the money you will save is worth the wait....

I built the DIY control piece of cake. took all but 45 minutes and bingo a usable dew control






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