Homemade Heated dew shield

[Astroblagger]

I wanted a heated dew shield for my C9.25 OTA, as the corrector plate dews up eventually, but didnt want to spend much money, i already had a perfectly good dew shield so i thought i might modify my dew shield to incorporate a dew heater. Im sure its been done many times before but thought I would log everything as I went along.

Materials/gear required-

330 ohm 0.5w resistors X50 (eBay £1.50)

RCA plug (maplins £1.19)

Heat shrink (not essential B&Q £3)

2 lenghts of wire, speaker cable (just had these lying about)

Soldering iron and solder (already had but cheap to buy)

Needle and thread

First thing i had to do was to cut a slot in the dew shield where it fits around the OTA as the Baader dovetail sticks out slightly and is in the way which stops the dew shield touching the OTA snugly all the way round. Just be aware that when the heater band is fitted it it will increase the diameter slightly of the dew shield.

Then i took out one side of the stitching of the supporting band on the dew shield, to give me access too put the heater strap inside.

The 330 ohm resistors were wrapped around the 2 lenghts of wire 16mm apart effectively to create 16mm squares., then soldered them and excess wire snipped as shown. At this point I rigged it up to my 12v power pack through my dew controller and measured the amps drawn with a clamp meter, just to check everything was in order.

I then connected the speaker cable, soldered and heated the heat shrink just to eliminate the chance of any short circuits, I then fitted the “resistor ladder” to the inside of the dew shield band

I then stitched the dew shield back together, tested it and it produces a good amount of heat, so just need to try it out on a dewy night now!

[g0ibi]

Very clever, let us know how it works outside!!

[beamish]

I love these sorts of projects , well done , very neatly carried out and I may follow suit

[Astroblagger]

The astrozap heated dew shield is £64 so built mine for under £6, will test it outside if the clouds ever leave!

[Gina]

Nice neat job

[MushroomBill]

Nice idea. Thanks I shall give it a go.

[Rols]

Shout very loud if that works well and i will jump on the wagon...

Great way of doing things i hope it works as good as it looks.

[lquinlan]

That's a really neat idea. I'm a newbie and dew on my secondary is starting to become an issue for me.

Excuse the silly question: what's a 'dew controller'? Just a simple power supply or does it have some regulation/thermostatic features ?

[Astroblagger]

you rig it up to your 12 volt power supply and can controll the current and hence power and heat output of the heater.

[pritc]

Nice!! Very Nice...

Great DIY project.

I think a few will be copying this.Including myself

Wayne

[Tron]

Can it make Toast too?

Maybe you should line some boots with those too, heated boots

[Gina]

Ah... heated boots! MMmmmmm :)

[Petrol]

Great idea, ordered some resistors

Am I right in thinking that 50 X 330 ohm resistors in parallel will pull about 1.8A at 12v resulting in about 21W of power?

Thanks

Pete

[JCJC]

We found this a (more than) useful guide, Build a Dew Heater from Resistors - IceInSpace

In the end we used nichrome wire (from ebay) in heatshrink snaked between 2" velcro.

JCJC's dad

[beamish]

Take a looksy here guys , easy to follow method, also look at this

just ordered 4m for 1.98 from fleabay 24swg Nichrome wire -far less soldering !!

eBay - The UK's Online Marketplace

perfect for a 11" sct

[Merlin66]

I used the Ni-chrome wire for a heater on the 12" Lx. Laid into a velcro strip - works well.

[Astroblagger]

Well they are all good guides on how to build a dew heater!! but i went for the simplest with out any real electrical knowledge required:)