8472 Posted December 16, 2012 Share Posted December 16, 2012 After a few night's observing being cut short thanks to dew forming, I set about making a dew heater for my Telrad (as done previously by someone else on SGL) but without any insightly exterior wiring. First I needed to source the parts: A suitable resistor (10ohm, 2w metal film) A small panel mount switch to turn it on and off as needed Heatshrink to encase the resistor in A twin AA battery holder Then its simply a case of: 1) Cutting a hole in the side of the Telrad to mount the switch 2) Sliding out the Telrad's glass and drilling two small holes to poke the two ends of the resisor through 3) Covering and shrinking the resistor with heatshrink, leaving the ends bare for soldering 4) Poking the ends of the heatshrunk resistor through the holes, then soldering everything together, including the AA battery holder. Luckily, there is just enough room for the two sets of batteries inside the Telrad, so I've no need to mount them externally. Job done and total expenditure well under a tenner. Sorry there are only "finished article" pics again! The heating element, just behind the Telrad's glass... The extra set of batteries to power it... Link to comment Share on other sites More sharing options...
Brantuk Posted December 16, 2012 Share Posted December 16, 2012 Another brilliant solution to a common problem - you'd really think they'd incorporate something like this on the manufactured model. It's hard to believe they don't know about the effects of dew on astro gear. Nice one again Kev Link to comment Share on other sites More sharing options...
Doc Posted December 16, 2012 Share Posted December 16, 2012 God Kev you are full of wonderful ideas tonight. Link to comment Share on other sites More sharing options...
Rusty Strings Posted December 16, 2012 Share Posted December 16, 2012 Crackin', love the switch. Link to comment Share on other sites More sharing options...
8472 Posted December 17, 2012 Author Share Posted December 17, 2012 Thanks, as always. On testing, I find it takes roughly 10-15mins to competely clear dewed up glass, but no time whatsoever, if it is switched on from the start. Should last as longer than I can keep my eyes open for, on fully charged batteries, too. I'm now turning my attention to something else on my scope that has always bothered me - watch this space, as they say... Link to comment Share on other sites More sharing options...
Perkil8r Posted December 17, 2012 Share Posted December 17, 2012 Awesome idea, love it. Link to comment Share on other sites More sharing options...
cosmic dave Posted December 18, 2012 Share Posted December 18, 2012 Thanks, as always. On testing, I find it takes roughly 10-15mins to competely clear dewed up glass, but no time whatsoever, if it is switched on from the start. Should last as longer than I can keep my eyes open for, on fully charged batteries, too. I'm now turning my attention to something else on my scope that has always bothered me - watch this space, as they say... Looking forward to what's coming next Link to comment Share on other sites More sharing options...
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