8" SCT dew heater: looks OTT but works fine!

[ejp1684]

When I bought my Evolution 8 I also bought an Astrozap combined dew shield and dew heater for it. But it wasn’t always successful. On very cold nights and heavy dew nights it just didn’t keep dew from forming on the corrector plate.

I found some suggestions on a US forum where the advice was not to put the heater on the metal at the front, but just behind it on the actual tube. The reasoning was that it needs a lot of energy to heat the front metal as it is quite thick. Much better to heat the tube just behind it which will then radiate heat onto the corrector plate.

I then found this web site which gave further information on actually making the dew heater. This suggested basing the power on 0.3 watts per cm. I worked out I needed about 21 watts, which equated to a maximum 1.6amps at 12v. I selected the gauge of nichrome wire so I could run it up and down the heater four times to make sure the heat was distributed evenly.
I followed the suggestions and used duct tape, and wired it up. I made a small box on my 3D printer to hold all the connections and a 2amp fuse. I ordered an LED Strip Inline Dimmer switch from Ebay for £4.50 so I could vary the power.

When using the Astrozap heater I noticed that it kept dew from forming on the outside of the dew shield - obviously a complete waste of energy. So I found a piece of foam from an old diy project, 2cms thick, cut it into sections and attached it with heat resistant tape. The whole thing then had an outer layer of duct tape, and is held in position with velcro.

I’m pleased to say that it works fine. The other night I had it on half power and dew began to form on the corrector plate. I put it on full power for ten minutes, the dew had gone and I then ran it succesfully for the rest of the session on three quarter power. Dew was forming on the top surface of the heater, so it looks like the insulation is working well. Total cost was about £16.

Eric.

 

 

[Dave In Vermont]

I like "home-brewed" gear the best! As the more bizarre and strange-appearing it is - the better.

An old friend of mine lived in a neighborhood with a lot of break-ins and theft. All of his electronics were at least partially 'home-brewed' stuff (he was an electronics wizard!), and none of it had regular covers or appearances: His once-Sony TV-set was a jumble of wires and circuits on a desk that was operated by shaking a bunch of keys on a key-chain a certain number of times - for different things like changing channels or volume.

A burglar or two broke-in now and then - but never walked off with anything. Probably afraid they'd be electrocuted on-the-spot!  

Dave

[SonnyE]

It's a shame they weren't, Dave. Good Riddance!