help with dew heater.

[Martin Whitaker]

Hi there, as a new member and owner of a Celestron cpc, I have been reading the posts on dew forming on sct's.

things have changed rapidly with the end of summer and heavy dew is forming most nights.

I have a meade sn. and made a dew sheild from a flexible camping mat, some type of dense foam.

This did hold off the dew for approx one hour longer than not having one but the dew finally shows its presence and stops the show.

I have been researching home made dew strips and dew strip controllers.

Does any one have experience of making either, if so can you advise on how best to proceed/ point me to a web site with info.

Unless I will be risking damage to my new scope I thought this would be a worthwile project not that i am any way an electronics wizz, but managed to convert a toucam for long exposure 2 yrs ago.

I have a Maplins store in the town where I work and they probably have the bits.

Appreciate any advice.

Cheers.

[bus_ter]

I found a video guide on YouTube the other day (at work now and youtube is blocked so can't find it). However in the end I just bought one. If you're on a budget try just a dew-not band connected direct to a 12v supply.

[Bigwings]

I managed for 2 years with a hairdryer...My 8"SCT did well with this and a corrugated cardboard dew shield. Real budget solution....

[barkis]

I made my own to suit various apertures.

I bought two reels of Nichrome wire, which is sold at varying Resistance per metre. Of course the length has to be cut to the power you need. Since the supply voltage is usually the standard 12volts. it's easy to work out the resistance, and the Watts.

W= V2/R.-----V=I*R----V*I=W----V/R=I (The first formula means Watts = Voltage squared divided by resistance).

W=Watts.. V=Volts---I= Current----R=Resistance.

I bought some broad webbing roll from EBay, some self adhesive fibre glass tape to stick the wire to the webbing, Sandwiched it all with another length of webbing, and my wife sewed them together for me, after I had soldered a length of twin cable to each end of the wire. I had Velcro hook and eye tape stitched in too, for easy attachment to the tubes.

Attached RCA Phono Connectors, and Bobby's your Uncle.

Ron.

Just seen this thread, so perhaps you will get help here too.

http://stargazerslounge.com/diy-astronomer/115742-dew-heaters-project-happens.html

[Martin Whitaker]

Hi there, thanks for your help everyone, not sure what to do for the best, the hair driers are quite cheap off e.bay,barkis did you make a controller or buy one, as I understand it the heater strip must be regulated so as not to interupt seeing due to over heating.

Have seen some sites showing basic resisters soldered on to wire, but none with Nichrome wire, is this what's inside a toaster by chance.

Cheers.

[blinky]

You could nip to your local Maplin's store and buy one of the kits described as a 'motor speed controller' it is a PWM (Pulse width modulated) controller and works by sending pulses of electricity to control the heat output.

[Martin Whitaker]

Hi blinky, just looking in Maplins catalogue and see a 'panell mounted speed regulator' with pulse modulation ,is this what you mean.

If yes then have you used one and if so what else will I need besides heater strip connectors, is it one regulator per heater strip.

Actually looked at your site images yesterday and thought they were amazing, if only I could do half as well.

Cheers.

[martin_h]

The maplin controller will handle up to 3 amps so it realy depends on the heater(s) you are going to connect to it as to how much current they will draw.