dew heater controllers

[chrisg18]

recently bought a c9.25 . which are the best dew heater controllers hitecastro or astrozap? I haven't encountered dewing up yet but im sure I will lol. many thanks.

[michael8554]

Before shelling out on a dew strap and controller, make a Dew Shield out of a foam camping mat, and see how you get on, may be all you need.

I have one on my 8" SCT, and a dew strap too, but can't remember when I last had to switch on the strap.....

Plenty of how-to's if you google.

Michael

[chrisg18]

ye got one already . how long have you used your sct for ? different conditions? winter ?

[damnut]

Hi Chrisg,

Would not go out winter or summer without a dewshield the corrector attracts dew like flies to doggy doo doo.

[Feral Rabbit]

I use to use an unheated dew shield but if I was on the lawn, within a couple of hours, I would have terrible dew build up. If I was on the tarmac at my house then I could get away without dew for 5 or 6 hours dependant on the weather conditions.

I was bought these for an Christmas present and I haven't had any problems. Just a word of warning if you do get one of these dew shields, is to not roll it up tight as it will crack.

The dew controller I have has a separate power out socket that I use to power my AVX mount. This allows me to only have to use one supply socket to power both the dew shield and the mount meaning less wires to trip over when dancing around the mount at night. I got the power lead from, I think, Modern Astronomy. Although I have an awful memory.

Dew Controller

Dew shield

Pleased with both of my presents

Hope this helps

Regards

[faulksy]

i had the cpc 9.25, a few hours in the valleys and everything looked like m31. i used the hitec astro which worked fine, i then made my own which allowed heat for the corrector,finder and eps

[JeremyS]

I use a Kendrick dewheater on my C11 which is mounted in an observatory - and I leave it powered on all the time. Before I used it, I did get dewing from time to time, especially on autumn evenings. But that's all a think of the past. 

I can attach several heater bands to the same unit, so I also have one for my GOTO hand controller (an extra benefit is that it's not freezing cold on the fingers in winter!)

Go well!

Jeremy

[Jimtom]

I made a dew-shield for my 6" SCT from a camping mat from Argos. Can't remember price but about a fiver. It's brilliant! The "flies to doggy doodoo" analogy is spot on Never had dew problems with my old Tal Newt, but that big lump of glass on the SCT is just asking for it. Anyway I can get over 2 hours on my wet lawn on a bad night but to be sure I've just picked up a 3 channel controller and strap which was custom made by a friend inthe village, looks like the proper job!

[chrisg18]

was he the only gay in the village lol.

[jonathan]

I use the AstroZap dew shields and heater tapes with HitecAstro four channel controller with two power outputs on my 8SE, so far works well.  My AstroZap dual channel controller broke (the electronic components failed) for no known reason, think I managed to repair  it but at considerable cost (had to buy replacement components from the USA).  At least on the HitecAstro I have four channels instead of two to go at, twice the fault tolerance for the same money.

[chrisg18]

thanks for your all your replies

[Tim99]

Check out the DewBuster.  I just bought that controller after talking to a friend who has it and really likes it.  It may be more expensive than some of the others but it comes with temperature sensors for the scope and air temperature.  Makes sense to me.  DewBuster.com.

[Tim99]

I have the Celestron Edge HD 9.25 and the first time out, the dew set in and it was game over. ( Even with a dew shield in place.)  I came home and immediately ordered the DewBuster and Dew Heater Strip for the scope.  I plan to make heater strips for the diagonal, eyepiece, finder scope etc.  He gives you instructions on how to build them on his website.  

[cjdawson]

I made my own dew heater.  I'm currently in the middle of rehousing it (have it combined with the supply power for my scope, Autoguider, and other accessories.)  I think you'll find that heaters generally fall into a few catagories...

1. Simple

These simply turn on and off, you cannot control the temperature (very few and far between, usuallly homemade projects)

2. Rheostat controlled.

The Rheostat is used as a knob to control temperature, the problem is that what's not put into the heater is put out as heat (homemade, not power efficient)

3. Pulse Width Modulator (PWM) controlled

The knob on the controller adjusts the pulse width, which determines how long the element is on for in a cycle.  (homemade and commercial, very power efficient)

Simple versions have a low frequency, these can cause the power to ripple  so it's not a good idea to run other things off the same power source as the controller.

More elaborate versions run at higher frequency this causes the ripples to be much smaller, as the frequency goes up, the ripples tend to even out. (I'm keeping this in laymans terms)

4. Intelligent.

These take the controller to the next level, they can calculate the dew point, and with the sensors placed in just the right spot, they'll control the PWM automatically.

The idea of these is to turn them on and forget they exist, you'll never need to adjust them as they do that part for you.

(some homemade, but most are commercial)

As I said, I made my own controller, it's currently a single channel PWM, based on a Vellman K8004 The circuit wasn't hard to put together - the instructions were good.  So much so that I made two of them

I've got them setup so the pulse frequency is about 4Khz, when I've checked this with my scope, it runs without any issues, so I can share the power source (70Ah leisure battery)

The real reason for using this as opposed to anything else was the whole "Efficiency: better than 90% at full load" so when I'm running my heater at 10% it's actually using alot less power than if I were running it at 100%.

[chrisg18]

thanks for your replies

[chrisg18]

received my hitecastro controller today and ota band.how much current will it draw from my 17ah powertank? 3amph maybe?