dew heaters

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speedy21
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dew heaters

Post by speedy21 »

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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Brian
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Re: dew heaters

Post by Brian »

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,
Brian
52.3N 0.6W
Wellingborough UK.

254mm LX90 on Superwedge, WO ZS66SD, Helios 102mm f5 on EQ1, Hunter 11x80, Pentax 10x50
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speedy21
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Re: dew heaters

Post by speedy21 »

Thank you for your advice dose any one by chance do both as a set
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David Frydman
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Re: dew heaters

Post by David Frydman »

Speedy21,
Isn't your telescope a Newtonian with just a mirror at the bottom.
Maybe the diagonal mists up?

Regards, David

speedy21
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Re: dew heaters

Post by speedy21 »

It's the secondary mirror that mists up after a wile then starts to restrict the vewis
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David Frydman
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Re: dew heaters

Post by David Frydman »

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

Brian
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Re: dew heaters

Post by Brian »

Speedy, have a read about secondary heaters here:

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

Regs,
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

speedy21
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Re: dew heaters

Post by speedy21 »

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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David Frydman
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Re: dew heaters

Post by David Frydman »

Make sure the hair dryer is safe outdoors in damp conditions and the cables on wet ground.
Are there cordless ones?

Regards, David

Brian
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Re: dew heaters

Post by Brian »

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.......
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

speedy21
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Re: dew heaters

Post by speedy21 »

Thanks for your advice I think a travel hair dryer sounds like the cheapest head ach free option
Skywatcher 200p explorer EQ5 mount synscan upgrade kit
Nikon D3100

brian livesey
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Re: dew heaters

Post by brian livesey »

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.
brian

speedy21
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Re: dew heaters

Post by speedy21 »

Thanks for that will be looking in to that wile this rain keeps coming and won't stop
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speedy21
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Re: dew heaters

Post by speedy21 »

Would the dew shield help with taking pics as I'd like to have a go at that this year
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brian livesey
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Re: dew heaters

Post by brian livesey »

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.
brian

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