Controling dew, help?

[Greymouser]

I know it is another stupid question, but I just do not know...

I have never really had much problem from dew when I was using my 6 inch Reflector or now with my refractor, but I think this will change as we head into winter. This will become even more the case as I am about to buy a Celestron Evolution 9.25 telescope and have been told that they are prone to dewing up more than some, are they? Just how much heat do I need to put into the 9.25" SCT?

Anyway can someone tell me the best way to be prepared please, because I assumed that a dew shield of some sort would suffice. I have seen the Astrozap flexi heat dew shield; straps and controller, but I have no idea how good they are and if I should get some straps too. On the controller it saws it can draw upto 8 amps, so that implies that it will need to be mains powered really, doesn't it?

 

[reezeh]

8A does seem like a lot, but if it is 12v then a deep cycle battery might be the thing. A combo of a dew shield and a strap heater set on low should keep the dew off. The general trick is to apply the minimum heat that'll stop you fogging up. Too much heat will probably ruin your seeing at best. By the time any dew forms you'll be ready to call it a night anyway.

[Waldemar]

This one : https://www.primalucelab.com/astronomy/dew-shields/astrozap-heated-dew-shield-for-celestron-9-25-inches.html  works great.
I had one for my C-11. Never had problems with dew because of it.As you can see it only draws 14 Watts or 1,18 Amps. and that is with continue on.
With a controller it will use less. Here it is a lot cheaper but less info: https://www.telescopesplus.com/products/astrozap-flexi-heat-dew-shield-with-notch-for-9-25-evolution-telescopes-az809-e

[Greymouser]

Thank you for the answers. ?

That shield is £ 73 from FLO, so if I am getting it it will be from there. It is good to know that it is only 14 watts too.

The Evolution scope mount has an inbuilt battery too, so I wonder if it could be run off that, or whether it would draw too much when combined with powering the mount. 

[Handy_Andy]

I have an 8" edge and made my own dew heater strap with nichrome wire. I made it to draw up to 1amp and that's more than sufficient to keep the dew off with a standard shield. HTH

Clear skies 

[Greymouser]

What do you power it with?

[Handy_Andy]

I have a deep cycle battery hooked up to a distribution board I made. Went with Phono plugs and sockets with variable resistors so I can lower the current. But you can choose your own plugs and such to suit your power supply.

Dew control is top right of my board

[Owmuchonomy]

I have a 9.25” Celestron SCT. It is correct they are dew magnets. I use a Celestron dew shield that came with it and a Kendrick dew band rated at 2 amps max. 8 amps seems an awful lot. In extreme cases even this set up is inadequate in which case I resort to my daughter’s cylindrical hair dryer. Two minutes of this applied inside the dew shield and it’s good for another hour or so.

[Swamp Gas]

Got a 6 inch nexstar, dewed up a treat but now I use an astrozap band on the end of the tube and wrap a DIY camping mat dew shield (£1) around it held in place with elastic. I also have an astrozap for the eyepiece end and power both off a battery a bit like this https://www.amazon.co.uk/TalentCell-Rechargeable-3000mAh-Lithium-External/dp/B072HR211P/ref=sr_1_16?ie=UTF8&qid=1537217871&sr=8-16&keywords=12v+battery

I have a 4 channel dew band controller and have them both on approx 4 to 6 hours a night and I can't even remember the last time I charged the battery. Seems to last ages. Only thing I had to do was put a different connector on the power end of the dew controller to make it fit the battery.

[iapa]

On 09/09/2018 at 19:02, Handy_Andy said:

I have a deep cycle battery hooked up to a distribution board I made. Went with Phono plugs and sockets with variable resistors so I can lower the current. But you can choose your own plugs and such to suit your power supply.

Dew control is top right of my board

I really like the idea of the constellation map in the board.

brilliant