Dew heaters

Folks - I've asked this before so sorry for repeating it...

Anyone have a personal review of a dewheater system they own or have used/seen? I'm in the market for one. I'd like computer control if poss (not sure if that limits me to Kendrick only...) but its not essential.

Cheers

Dave

Is there a limit to the Kendrick one for you Dave? Any thoughts on it? I don't have one, but if I was to get one, I've only ever heard of Kendrick...

I have no preference for the model of dewheater. I just want quality ( :roll: ) at a good price.

I think there's a couple of controller manufacturers and a few more who can supply the heating element (tape).

The only one I know of that can be contrrolled thru a PC is the Kendrick though...

Cheers

Dave

Dave,

Initially, tried making one, but found it was taking me such a long time with resulting in erratic behaviour. So I stopped and bought the Kendrick. It was really worth the time and money in the end.

The Kendrick dew heaters I have are the analogue ones. They have worked fine with my set up here. At least you can select the lengths for your lens dia., be it corrector lens or eyepiece holder size. Its handy having the option of 4 out put leads to different size heater resistent straps.. One mistake I made initially was to extend from the control box an extra 20 feet. I found it was not attaining the heat required to reduce the dew. In addition of having so many starps trying to get heated up. This was due to slight resistence in the cable I had connected too. I use 5-7 AMP power supply from CPC. The Kendrick one I found too expensive.

I looked at the Kendric again for another application. This time I had a large area to heat up, ie. a secondary mirror and the Kendrick system had a different configuration. ie only the straps. However, they are selling the secondary dew guard from a company called AstroSystems whom specialise in secondary dew guards. These are specifically for your secondary mirror, ie placed at the rear. Unfortunately, my rear design of secondary has a permanent stalk at the back. It would have been nearly impossible to connect the dew guard. You have to bond it on to the glass. I couldn't do that in my case.

The answer came before Xmas when I was in Lidls store. I saw a pillow warmer for €12 with a selector switch for levelling the heat off. This now is a recent working part for the secondary mirror. What a gift! What a saving! The pillow warmer is so small that you could also wrap it around a finder telescope.

Another idea I had for a SCT solid tube for insulation was to use a single bed warmer. They also could have been bought in Lidl for €20. The idea would be to wrap the tube with this. At present I am using a passive dew shield which is quite adequate for providing at laest 6/7 hours without dew. This design is made up of bubble pack sheeting of a certain thickness, one side is then sealed with silver mylar film, the other side has felt stuck on. Again the idea is to wrap the telescope tube with this item. Velcro can used to seal it.. The silver mylar side faces out. This works extremely well.

Thats my 2 cents worth!

Eamonn A

Dave,
I have the kendrick dew heater system, the analog version, I have found that it doesnt prevent dew forming, especially near the secondary mirror, even when up full, you still need a good dew shield.
I've heard that the folowing dew shield is very good, I would have got it except its abit awkward when you take counterweights into the equation.

www.dewbuster.com/dewshield/dewshield.html

Dave L,

Thats an excellent description of making a dew shield. Your right, you do need the dew shield combined with the Kendrick system.

I was surprised that his website version doesn't fully cover the length of the SCT. Also to extend it 50% beyond the length of the tube.

I felt it was an advantage to fully wrap the tube, thereby providing even insulation throughout the length of the tube. By extending 50% beyond the corrector prevents due.

I take your point about the obstructions. I am using a german mount with ring saddles. I stripped the felt from the inside of the ring saddles. The insulation was designed in parts, so as to get round any obstructions, not easy. The other problem I have found is that the shield tends to slightly sag. I am looking at an inexpensive solution. Looking around for something similar to Kydex, ie. easy flexible solid sheeting that can be configured into a tube. This would prevent distortion in the shield. The prices for Meades dew shields are astronomical ie. the ones that just extend out beyond the tube.

Eamonn A