Dew control on a budget.

[ryandsimmons]

I have recently upgraded from a Reflector to a CST and I suddenly get this dew problem that I have read about fairly frequently.  I was just wondering if someone could explain to me as if I was an idiot exactly what I need to do to prevent this misting up?

I am currently making a home made dew shield which I understand will give me 30 minutes or so grace, however looking online there are other solutions that are better?  However I am getting confused as to what exactly I need, there seem to be several bits and I am struggling to find a simple "buy X, Y and Z" type instructions.

I am also rather broke at the moment, so even better are there DIY type guides to dew control around?

Many tahnks

Ryan

[ChrisLX200]

The shield will help but somehow you need to add a little heat so the corrector plate is held fractionally above ambient temperature. The minimum amount of heat necessary to do the job, and put in the right place is best - which means applying it to the outside of the tube very close to the edge of the corrector plate itself. That is usually achieved with a strap wrapped around the tube and connected to a variable power output controler.

Yes, there are DIY solutions involving nikchrome wire or a string of resistors wired in series, and if you are competent at a bit of soldering then it can be done. I don't have a link to hand but a google search will throw up many results. You do need to be careful not to use too much heat with a DIY approach as that will degrade the optical performance.

chrisH

[laser_jock99]

Hairdryer.

[brantuk]

As per above - hairdryer on medium heat to clear any dew already formed, dew controller to drive the band(s), and some bands. Good idea to make a dew shield - use that as well as the bands for best effect. Then if you need to use the hairdryer again you're getting close to session packing up time.

[IanL]

Here's the "why it happens" bit:

http://www.blackwaterskies.co.uk/2013/05/dew-formation-and-prevention.html

Here is everything you need to know to build your own dew heater bands.  Nothing is left to the imagination, full instructions and a spreadsheet to help you design it, shopping list plus illustrated instructions on how to make the thing. It can be done for a few quid if you have access to a soldering iron (and even that can be avoided if you use fishing line crimps).  You do need a basic multi-meter, but that should be pretty easy to borrow if you don't have your own:

http://www.blackwaterskies.co.uk/2013/05/making-your-own-nichrome-dew-heater.html

Here's how to build a dew heater controller for maybe five quid, or perhaps 20-30 quid if you want the 'deluxe' model:

http://www.blackwaterskies.co.uk/2013/05/a-cheap-multi-channel-dew-heater.html

I have been using my heater bands and controller for two years now on both refractors and an SCT.  The wife's hair-dryer misses its midnight outings however.

[JCJC]

If you are thinking of making your own heater bands (quite easy) then this is one of the best guides, there are others.

http://stargazerslounge.com/topic/185968-led-dimmer-dew-controller-full-write-up/

EDIT: almost quick enough !

JCJC' dad

[ryandsimmons]

Thanks very much guys!

Looks like I have a summer project!

[faulksy]

The shield will help but somehow you need to add a little heat so the corrector plate is held fractionally above ambient temperature. The minimum amount of heat necessary to do the job, and put in the right place is best - which means applying it to the outside of the tube very close to the edge of the corrector plate itself. That is usually achieved with a strap wrapped around the tube and connected to a variable power output controler.

Yes, there are DIY solutions involving nikchrome wire or a string of resistors wired in series, and if you are competent at a bit of soldering then it can be done. I don't have a link to hand but a google search will throw up many results. You do need to be careful not to use too much heat with a DIY approach as that will degrade the optical performance.

chrisH

resistors wired in parallel   

[Oily]

Or just order the kits from Duncan:

http://www.dewityourself.co.uk/

[ChrisLX200]

resistors wired in parallel 

Nope, mine were wired in series so the whole chain of them combined gave the right resistance for the required heat output.   They were then threaded into a rubber tube to keep water out, and it worked fine.

ChrisH

[faulksy]

Nope, mine were wired in series so the whole chain of them combined gave the right resistance for the required heat output.   They were then threaded into a rubber tube to keep water out, and it worked fine.

ChrisH

right fair enough, but if 1 fails the whole system goes down