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Old 11-06-2020, 02:13 PM
Granada
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Dew control

What sort of dew control equipment would I need for a Skywatcher Refractor ED 120? I've got a power station with 2 cigarette lighter sockets that I can use.
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Old 11-06-2020, 03:58 PM
Startrek (Martin)
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Do you image or observe or both ?
A 4 channel dew controller (eg: Orion dewzapper )and Velcro heater bands will suffice
Kendrick is quality brand ( Canadian)
Available from most reputable astronomy suppliers like Bintel
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Old 11-06-2020, 04:01 PM
Granada
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Quote:
Originally Posted by Startrek View Post
Do you image or observe or both ?
A 4 channel dew controller (eg: Orion dewzapper )and Velcro heater bands will suffice
Kendrick is quality brand ( Canadian)
Available from most reputable astronomy suppliers like Bintel

Yeah I should have specified, this one is just for astrophotography. Thanks, that helps!
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Old 11-06-2020, 05:01 PM
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mental4astro (Alexander)
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You don't need heat for dew control!

With this method, not only are you not introducing heat into your thermally stable scope, you also use less power:

Refractor dew control WITHOUT heat - it is possible

Where I live evenings can be veey dewy. I've been using this method for several months now with my Mak and refractors, and no dew issues while dew was dripping off the tube.

Heat does have a place, but it should not be on our scopes. We fuss to get our scopes to thermal equilibrium, and then we go and stick heating elements on the scope. Professional observatories do not use heat to control dew.
Alex.
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Old 11-06-2020, 05:14 PM
Startrek (Martin)
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Iíve imaged with and without thermal dew control and canít see any obvious differences in my final images or maybe my eyes are getting old
Interesting method of dew control , worth looking into
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Old 11-06-2020, 05:23 PM
Hodur (David)
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The yukky high level mush that passes for cloud, combined with dew has all but driven me away from Astro. Iím thinking the only solid way of getting results in Sydney are with an Ob.
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Old 15-06-2020, 04:37 AM
Renato1 (Renato)
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On my Skywatcher 120mm Achromat (and every other telescope I own), I use a 12 Volt hair dryer that I plug into into a car battery starter.

It costs about $24 on Ebay.
https://www.ebay.com.au/itm/12V-Hair...0AAOSwX1xc3nC9

On nights when everything gets covered with dew, I just blow the warm air on the objective lens, finderscope, red dot finder and eyepiece. This is usually good for another 15 to 20 minutes of viewing.

Only problem one can have is that the hair dryer might not work when plugged into the cigarette lighter sockets of various power units, some of which cut out when that much power is drawn from them. This doesn't happen with my Projecta car battery starter, but did happen with a cheap battery starter unit from Aldi. Solution there was to buy a 12 Volt socket extension cord, cut the base off, separate the wires, strip the two ends, and attach them to the jump start cables (or even cheaper, cut the 12 volt plug off the hair dryer, and attach its wires to the jump start cables).

To stop the refractor and finderscope from dewing over as quickly, and to extend the time between having to blow dew off, many years ago there was an article in Sky and Telescope showing how attaching aluminium foil to dew shields stopped them dewing up as quickly. So I made dewshields out of plastic from cheap folders for my finderscopes, then attached aluminium foil to the rolled up little dewshields, covered my Telrad units and their dewshields with that foil using Blutack, and also used BluTack to stick aluminium foil to my telescopes' flexible dewshields. This worked and I though it a worthwhile exercise back in the days when I did heaps of viewing in all night sessions. But as a mainly intermittent viewer nowadays, the 12 volt hair dryer is good enough for me.
Regards,
Renato

Last edited by Renato1; 15-06-2020 at 04:58 AM.
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Old 15-06-2020, 08:24 AM
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Clever use of alfoil. Apparently it also works to stop aliens from reading your mind. ��
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Old 15-06-2020, 12:49 PM
Renato1 (Renato)
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Clever use of alfoil. Apparently it also works to stop aliens from reading your mind. ��
Alien mist creatures?
Cheers.
Renato
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Old 15-06-2020, 03:14 PM
glend (Glen)
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I am surprised the Coreflut Rappers have not made an appearance in this thread.

Just on the hairdryer use, those 12V ones do suck the juice out of a battery pretty quick and jumpstart packs have no staying power, usually only about 17ah for a quick surge for starters. A regular AC hair dryer is ok but turn the heat setting as low as possible and only use it for a few seconds to debug. Neither of those devices is a good solution for a night of imaging, where a good dew controller, like the Kendrick Astro one and the right dew strap, will keep your objective clear. Forget foil, it is fine for baked potatoes in an oven but useless in astronomy, as it is thin and sheds heat rapidly.
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Old 15-06-2020, 11:17 PM
Renato1 (Renato)
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Quote:
Originally Posted by glend View Post
I am surprised the Coreflut Rappers have not made an appearance in this thread.

Just on the hairdryer use, those 12V ones do suck the juice out of a battery pretty quick and jumpstart packs have no staying power, usually only about 17ah for a quick surge for starters. A regular AC hair dryer is ok but turn the heat setting as low as possible and only use it for a few seconds to debug. Neither of those devices is a good solution for a night of imaging, where a good dew controller, like the Kendrick Astro one and the right dew strap, will keep your objective clear. Forget foil, it is fine for baked potatoes in an oven but useless in astronomy, as it is thin and sheds heat rapidly.
Well, the good thing about aluminium foil is that it costs about $1.50 and everyone has some Blutack lying around. Thus it's a pretty cheap and easy exercise for anyone to test out in a side by side test (of Telrads or finders say) whether or not the foil works and either prove or disprove the S&T article.

A 216 Watt 12 Volt hair dryer draws 18 Amps.
A 17 Amp-hour battery should supply 18 amps for 56.6 minutes.
I use my 12 Volt hair dryer on my refractor and accessories for three or four minutes at a time when I'm using it.

Which is sufficient for three to four hours of viewing, but probably not good enough for very long sessions. Would need another battery starter/power tank for that.
Regards,
Renato
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Old 16-06-2020, 06:03 PM
Kuz (Kuz)
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I personally would go with the kendrick heater. If is a esprit 120 you will need to purchase a 6 inch strap . I think of them as Cheap insurance. With the heater on you are actually heating the lens closer to ambient template. Eliminating the dew point factor where your lense can fog up. You only need to run the heater a few degrees either side of ambient temperature. I also use one on my guide scope to enable better tracking, dew free guidescope all night.
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Old 18-06-2020, 01:50 PM
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cometcatcher (Kevin)
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I use a cheap eBay coowoo 43cm USB heater strap on my 120mm refractor. Works great. Has 3 heat settings and draws less than 500ma. I give it lots of time before imaging to reach equilibrium. Also use one on the guide scope.
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