Dew heater options

[gregbradley]

I am finding now the weather is cooling off at night the occassional bit of dew on my secondary on my CDK17.

What dew heating options are good? I have never used a dew heater before.

My APOs don't seem to suffer from dew much. I did get a bit of dew on an FS152 but I got this insulation blanket you wrap around the tube where the lens cell is and it kept the lens a few degrees warmer than ambient and stopped dew. It worked really well. You could make one yourself with some windscreen heat savers - you know the ones with silver foil insulation blanket you put on your windscreen to protect your dash? Use a bit of Velcro so it can attach to itself after you wrap it around the OTA where the lens is.

Greg.

[Waxing_Gibbous (Peter)]

I'm not sure how much difference there really is between brands, but "DewNot" were recommended to me last year and the unit for my refractrors has proved effective and reliable.
I got it from either Sirius or Star optics (can't remember which).

[hikerbob (Bob)]

Greg I use the DewNot's (got them direct for just over haldf the price of local suppliers).

Unless your skill's are exceptional trying to make robust heater strap's which fit in with the practicalities of astronomy looks like a wasted effort.

You will also want some kind of controller, a range of options (I've made my own and published details in the Projects area as have others). Getting things too hot wastes power.

DIY generally involves some kind of PWM (Pulse Width Modulation) device, Jaycar and Ocean Control's both sold kit's which can be adapted. There are are also full blown unit's on the market.

Have a browse at the forum thread's in the DIY area for some idea's one what people are doing.

Bob

[Gama]

Greg,
You have an open truss system, which is whats mostly creating your issue.
Wrap the telescope in a shroud, and this should help out heaps.
I made a light shroud by buying some cheap dark cloth, and sewing (My Wife) some velcro along the side so i can remove and attach it to the truss.
Try this first, rather than wires and dew straps starting to occupy the spider.

Theo

[gregbradley]

Originally Posted by Waxing_Gibbous

I'm not sure how much difference there really is between brands, but "DewNot" were recommended to me last year and the unit for my refractrors has proved effective and reliable.
I got it from either Sirius or Star optics (can't remember which).

That sounds good. I'll follow that up.

Originally Posted by hikerbob

Greg I use the DewNot's (got them direct for just over haldf the price of local suppliers).

Unless your skill's are exceptional trying to make robust heater strap's which fit in with the practicalities of astronomy looks like a wasted effort.

You will also want some kind of controller, a range of options (I've made my own and published details in the Projects area as have others). Getting things too hot wastes power.

DIY generally involves some kind of PWM (Pulse Width Modulation) device, Jaycar and Ocean Control's both sold kit's which can be adapted. There are are also full blown unit's on the market.

Have a browse at the forum thread's in the DIY area for some idea's one what people are doing.

Bob

Thanks Bob. I'll check it out.

Originally Posted by Gama

Greg,
You have an open truss system, which is whats mostly creating your issue.
Wrap the telescope in a shroud, and this should help out heaps.
I made a light shroud by buying some cheap dark cloth, and sewing (My Wife) some velcro along the side so i can remove and attach it to the truss.
Try this first, rather than wires and dew straps starting to occupy the spider.

Theo

I already have the Planewave shroud on mine.

I think it only happens occasionally but of course when it does it affects the image.

I may have no choice on some cool moist nights.

While we are talking about CDKs, I was thinking of buying the reducer. Do you know of anyone who has used one and what
they think of it? I can't see any images taken with one on the net.

[Gama]

I also have yet to see any images from a CDK with the reducer.
I'd also like to see some examples.

Theo

[ballaratdragons (Ken)]

Originally Posted by hikerbob

You will also want some kind of controller, a range of options (I've made my own and published details in the Projects area as have others). Getting things too hot wastes power.

DIY generally involves some kind of PWM (Pulse Width Modulation) device,

Bob

Bob, (and others that make the same claim), why does a heating set-up necessarily need PWM.

I built mine without one and it's worked fine for the last few years. What is the need for it?

Sounds to me like an unnecessary item to make the DIY build even more complicated.

[hikerbob (Bob)]

Ken do you run of main's power or batteries?

I need to run of batteries sometimes and the PWM combined with temperature sensing keeps power consumption way down. I only heat when I need to heat.

Probably no big problem with eyepieces being warmer than necessary (might be nice on a cold night).

Bob