Kendrick Newtonian dew heaters? Anyone tried?

[SlipperySquid]

Hi I'm looking for a solution to the secondary dew problem on my Skywatcher 200p.

I know a lot of people have the same problem and I have at the moment a home made dew shield that's been doing great but the other evening everything was so wet that even the Shield didn't help, though my guide scope was dew free due to it having a heater band on.

Now I have found these KAI - Newtonian Heaters and was wondering if anyone had tried using them? I know there is the chance that the glue can melt on secondary mirrors (Does anyone know if this has actually happened or is it just urban myth) but I suppose this would only happen if the heater band was stupidly hot? or people in hotter climes with temps reaching high 30's to 40's would have there mirrors dropping off left right and centre.

Would love to know that these dew heaters where a viable solution?

Thanks to anyone that can point me in a dew free direction!

Matt.

[lukebl]

I had a similar problem with dew on my secondary, and now have a makeshift cardboard dewshield c500mm long. Not very pretty but it does the job. And it was free! Well, apart from the sellotape.

[NGC 1502]

Hi Matt, Like yourself I've made a dewshield for my Dob, which does the trick most

of the time. But I also use a 12v "hair dryer", it's almost useless for it's original purpose, but sorts the secondary when necessary. I point it down the focuser.

Maybe a secondary heater would be better, as it prevents the dewing rather than

cures it, but the hair dryer works for me.

I never leave home without it !

Cheers, Ed.

[SlipperySquid]

Yup the hairdryer is do-able BUT my neighbours won't appreciate it firing up at 1am

Also with me doing imaging it means removing the camera etc.

These bands being purpase built for the job in hand seem like a good option and I may bite the bullet and see if I can find a UK supplier and give one a try! (Anyone need a review )

Will have a look at my secondary and see which one would be best!

Matt.

[haitch]

Secondary mirrors are more usually stuck on with silicone, I think, which shouldn't melt.

I was out the other night and couldn't understand why the view was so bad until I went to put it away in despair and saw the secondary looked like a frosted window.

When I got my mirrors back from re-coating I fitted several resistors inside the Secondary housing and wired them up to as socket in the back of it. Never needed it before but I guess I'll have to have a play with them now.

[lukebl]

Just wondered if there are any problems with the hair-dryer technique? I would have thought that the temperature changes (even subtle ones) would set up all sorts of air currents which would upset the viewing quality. And, of course, when the temperatures had stabilised, the dew would appear again.

[haitch]

I would imagine that the forced evaporation of the dew takes as much energy out of the mirror surface as a 12v hairdryer would put in.

If your mirrors just conducted heat energy to the atmosphere they would fall to ambient air temperature and stay there but because they radiate it as well they tend to fall below air temperature so it's all about achieving a balance.

[NGC 1502]

I think that whatever method is used to get rid of secondary dewing, we are

talking about very low heat levels. Of course, if the secondary is dewy to the

point of having water droplets on it, then basically it's time for bed !

The 12v hair dryer I use gets rid of misting up, and seems to last ok.

Some worry about heat damage, but as I've said, we are only talking about

very gentle warmth, which is why the 12v unit that I use is no good at all for its

intended purpose !

But prevention is better than cure, so a proper secondary heater (or very gentle

warmer !) is probably better.

Best regards, Ed.

[dogfish]

I like the look of those Kendrick secondary heaters. I was a bit confused by the different types. Anyone know which type for a SW 300 dobsonian and anyone in the UK who stocks them?

Cheers, Martin

[Astro_Baby]

You do get hot air cuirrents from anti-dew systems but its that or water running off the secondary - one is bearable the other is a wipe out.

I occasionally toy with a dew heater for the sescodary but dont really like the idea of wires running around the spider vanes plus the only time the secondary has dewed super bad so did everything else - the primary, the eyepieces the whole works so a secondary heater would have made no difference at all.

[haitch]

You do get hot air cuirrents from anti-dew systems but its that or water running off the secondary - one is bearable the other is a wipe out.

I occasionally toy with a dew heater for the sescodary but dont really like the idea of wires running around the spider vanes plus the only time the secondary has dewed super bad so did everything else - the primary, the eyepieces the whole works so a secondary heater would have made no difference at all.

I wondered about a secondary holder with a non-conductive centre and conductive vanes that could be used instead of wires to transmit the current

[Dai150PL]

I also have a major dew problem, so was thinking along the lines of the above comment and getting one of these - Protostar Telescope Making & Upgrading As well as a dew shield and heater bands. Would like to know if anyone has used this type of secondary heater.

[haitch]

Aaaaaaaaaarghhhh!

One day I'll patent one of my thoughts!!! (you can keep Windows 7... Microsoft Surface was my idea)

[SlipperySquid]

That Looks even bteter!!! Now how do I work out what I need for my 200P? Anyone