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 Post subject: dew heaters
PostPosted: Fri Dec 18, 2015 9:13 pm 
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Joined: Fri Oct 10, 2014 8:12 am
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Location: earby lancs
Hi can anyone help me I'm looking at getting a dew heater for my sw 8" but see the band's but don't see a controller with them do you need a controller or can they be used on there own would like to find out as much as possible before getting one and if this weather sorts it's self out thank you in advance

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 Post subject: Re: dew heaters
PostPosted: Fri Dec 18, 2015 9:27 pm 
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Joined: Fri Dec 03, 2004 9:58 pm
Posts: 3559
Location: Wellingborough
To get "set and forget" control of the heater temperature you will need a controller. I got one of these for my SCT dew heater and it works well:

http://www.rothervalleyoptics.co.uk/rot ... oller.html

Once the telescope tube has warmed little, only a low setting is needed to keep the corrector plate clear. Bear in mind though that a dew-band can suck up the current so if you run from a battery keep an eye on the state of charge :)

HTH,

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52.3N 0.6W
Wellingborough UK.

254mm LX90 on Superwedge, WO ZS66SD, Helios 102mm f5 on EQ1, Hunter 11x80, Pentax 10x50
ASI120MC Toucam Pros 740k/840k/900nc mono, Pentax K110D
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 Post subject: Re: dew heaters
PostPosted: Fri Dec 18, 2015 10:09 pm 
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Location: earby lancs
Thank you for your advice dose any one by chance do both as a set

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 Post subject: Re: dew heaters
PostPosted: Sat Dec 19, 2015 2:26 pm 
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Speedy21,
Isn't your telescope a Newtonian with just a mirror at the bottom.
Maybe the diagonal mists up?

Regards, David


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 Post subject: Re: dew heaters
PostPosted: Sat Dec 19, 2015 4:42 pm 
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Joined: Fri Oct 10, 2014 8:12 am
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Location: earby lancs
It's the secondary mirror that mists up after a wile then starts to restrict the vewis

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 Post subject: Re: dew heaters
PostPosted: Sat Dec 19, 2015 7:15 pm 
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Joined: Mon Jan 18, 2010 9:25 am
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The secondary mirror would need a very small heater.
Would this degrade the view?
Would a small safe hair dryer help with occasional blasts?

Others will tell you if diagonal heaters are suitable.

Regards, David


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 Post subject: Re: dew heaters
PostPosted: Sat Dec 19, 2015 8:33 pm 
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Joined: Fri Dec 03, 2004 9:58 pm
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Location: Wellingborough
Speedy, have a read about secondary heaters here:

http://www.kendrickastro.com/newtonian.html

Regs,

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Brian
52.3N 0.6W
Wellingborough UK.

254mm LX90 on Superwedge, WO ZS66SD, Helios 102mm f5 on EQ1, Hunter 11x80, Pentax 10x50
ASI120MC Toucam Pros 740k/840k/900nc mono, Pentax K110D
Ro-Ro roof shed


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 Post subject: Re: dew heaters
PostPosted: Sat Dec 19, 2015 8:54 pm 
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Joined: Fri Oct 10, 2014 8:12 am
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Location: earby lancs
Thank you for your input I'm just about to upgrade my mount to a go-to I've got the power supply unit the upgrade kit but got wait till Xmas for the upgrade kit but a hair dryer sounds like a good idea can you get one that runs on 12v like a camping one or work on a cigar socket as it would keep me compact and go anywhere on my power pack

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 Post subject: Re: dew heaters
PostPosted: Sun Dec 20, 2015 5:58 pm 
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Make sure the hair dryer is safe outdoors in damp conditions and the cables on wet ground.
Are there cordless ones?

Regards, David


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 Post subject: Re: dew heaters
PostPosted: Sun Dec 20, 2015 6:53 pm 
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Joined: Fri Dec 03, 2004 9:58 pm
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Location: Wellingborough
There are a few 12v camping hairdryers on Amazon for instance:

http://www.amazon.co.uk/s/?ie=UTF8&keyw ... lrlsp6xq_b

Again, 120W at 12V draws a 10 amp current from your battery.......

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Brian
52.3N 0.6W
Wellingborough UK.

254mm LX90 on Superwedge, WO ZS66SD, Helios 102mm f5 on EQ1, Hunter 11x80, Pentax 10x50
ASI120MC Toucam Pros 740k/840k/900nc mono, Pentax K110D
Ro-Ro roof shed


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 Post subject: Re: dew heaters
PostPosted: Sun Dec 20, 2015 7:21 pm 
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Joined: Fri Oct 10, 2014 8:12 am
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Location: earby lancs
Thanks for your advice I think a travel hair dryer sounds like the cheapest head ach free option

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 Post subject: Re: dew heaters
PostPosted: Mon Dec 21, 2015 11:01 am 
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Joined: Mon Jan 09, 2006 11:05 am
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Location: Lancashire
Dewing of the flat can be minimised by adding a foot-long dew shield extension to the top of the 'scope. I did this with a piece of camping mat, lined with matt black card, on the REVELATION 8-inch Newtonian. The main tubes of the SKYWATCHERS and REVELATIONS are too short at the top end.
The bottom of the main tubes could be an inch longer too, so that the mirror-adjusting screws are not sticking out.

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 Post subject: Re: dew heaters
PostPosted: Mon Dec 21, 2015 1:04 pm 
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Joined: Fri Oct 10, 2014 8:12 am
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Location: earby lancs
Thanks for that will be looking in to that wile this rain keeps coming and won't stop

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 Post subject: Re: dew heaters
PostPosted: Tue Dec 22, 2015 9:32 pm 
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Location: earby lancs
Would the dew shield help with taking pics as I'd like to have a go at that this year

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 Post subject: Re: dew heaters
PostPosted: Wed Dec 23, 2015 2:41 pm 
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Joined: Mon Jan 09, 2006 11:05 am
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Location: Lancashire
The dew shield extension can improve imaging by keeping stray light out of the main tube.
If we look down through the righthand edge of the eyepiece focussing tube ( assuming that the focuser is on the east side of the main tube when your 'scope points south ) without the eyepiece in and can see our hand at the top of the main tube, then the main tube is too short.

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