Alternative dew heating system

[subbuteorob]

Hi everyone,

I have just purchased a CPC 800 and was astounded as to how quickly dew hit  and restricted my view to nothing.  I live in the UK and near marsh so humiditiy is quite high.

Unfortunately when I ordered dew shields were not in stock. I obviously need a solution and a dew shield is part of it.

What would people recommend ?

Also a mad question I know but I have a heating belt for home brew purposes. Something similar to this :

http://www.the-home-brew-shop.co.uk/acatalog/Better-Brew-Heater-Belt.html#.VvE7qzHsS7Q

Could that be part of the solution instead of a dew heating system or am I completely bonkers to even think of it.

Go easy on me

 

Rob

[PeterCPC]

I think that might get too hot. This is what I use and they are brilliant. http://www.firstlightoptics.com/dew-prevention/astrozap-flexible-dew-shield.html

Peter

[subbuteorob]

Hi Peter

Thanks

do you use a heating system as well ?

why do you prefer the astrozap to Celestron's own dew shield ?

Rob

[Putaendo Patrick]

Many people make a cheap but effective dew shield out of a foam camping mat.

And yes, there are heaters which superficially look similar to your home-brew heater. They do however need a controller as temperatures need to be very minimally over the ambient. This company, among others, makes them:

https://www.astrozap.com/scripts/prodList.asp?idCategory=57

If you are good with "electrics", you can make your own.

 

[Physopto]

You can try a foam matt. I bought one in Aldi a few weeks ago. My intention was to cut out strips to further insulate the dew bands, as they really are poorly insulated. By doing so you can cut down on the power needed to stop dew forming. But the foam matt I bought would make a very good dew shield as well as it is very light and stiff enough to form a shield. Aldi may not still have them in but for £7 worth it.

Derek

[subbuteorob]

Patrick and Derek - thanks I am useless at DIY and so I would probably go with a shop bought solution.

[Physopto]

It does not take any effort to wrap a matt into a circle/tube around the front of a scope. A couple of big elastic bands will hold it. There is nothing special about a dew shield.

[PeterCPC]

25 minutes ago, subbuteorob said:

Hi Peter

Thanks

do you use a heating system as well ?

why do you prefer the astrozap to Celestron's own dew shield ?

Rob

The Astrozap has a heating wire in it. The Celestron Dew shield is just a shield - unheated. You would need a dew heater controller with the Astrozap. Something like this http://www.modernastronomy.com/shop/accessories/dew-control/single-channel-dual-port-dew-controller/

 

Peter

[subbuteorob]

Ah ok that makes sense Peter.

Derek ...point taken

[sungrazer]

I have a CPC925 and an Astrozap shield.  Personally i've never needed a heater as the shield copes well enough on it's own.  I bought the Astrozap as the Celestron was out of stock at the time, but having listened to a few people whilst out and about, most seem to prefer the AZ anyway.

*Caveat - I'm not near a large body of water/marsh!*

[MartinB]

I've had a variety of dew straps over the years, some fell apart (dew not) and some with cables too short (Kendrick).  Astrozap have been the best I've used they also do a nice simple controller.  One problem with camping mats is that they are great insulators so a heating strap will need to be placed lower down the tube.  

I've found that I need both a shield and a strap.  As soon as the scope starts pointing high in the sky some of the corrector plate is exposed to the sky and will start to radiate towards sky temp and dew can form.  I also prefer the flexibility of not having dew straps combined with a dew shield - you can use a 10" dew strap on a 5" scope but not a 10" shield (well not easily anyway).

[subbuteorob]

I think I will try the Astrozap shield and see how it goes. I can always add a heater later on.

Thanks all.

[MartinB]

Good plan, have a hair dryer to hand as well - essential "get out of jail" kit!

[Physopto]

12 volt hair drier! not 240 volt AC....

 

[ronl]

Your scope is a magnet for dew, but a dew shield will help to keep it at bay, keep all caps on your scope and finder while waiting for it to reach ambient temperature, keep your

eyepieces in your case with the lid closed, and the ones you will use the most, keep them in your jacket pockets, if one fogs up swap for one in your pocket, put the caps on the

fogged one and put that in your pocket, it will soon will be clear, you can get a hand warmer or two and put those in with the eyepieces, I live in the same area so I know what 

the dew is like, it is a pain, but my scopes are not as bad as yours are for attracting dew, the only trouble with heated dew strips are the wires, unless you get a battery pack as well.

[subbuteorob]

Thanks everyone .

Hi Ron, Many thanks for the practical advice. I have quite a lot of eyepieces now as I've kept them from my previous scope an 8 3/4 inch Newtonian.

I had no idea dew would be such a massive issue. I literally left my scope outside to get into something warmer came back 5 mins later and couldn't see a thing. Thought something had gone wrong as its a new scope.

Unfortunately there is another problem with the scope in that the Alt clutch has stuck and so it needs to go back for repair. Pretty sure it was too tight to start with. So not much observing for me in the next week or so but gives me time to sort out dew cap etc

Incidentally Ed at Harrison Telescopes who supplied the scope has been brilliant.

Robert