Dew Control

TV76 · #1 21-04-2015, 09:13 PM

Hi,

Was wondering if anybody in Adelaide has found is necessary to employ a dew controller during winter and if so what temperature does it need to get down to to warrant a dew controller?

The other night it got down to 5 degrees and the 5" refractor seemed ok but with winter planet oppositions ahead I've been giving this a bit of thought.

Any thoughts or related experiences most welcome.

Cheers,
Alec

britgc (Bret) · #2 22-04-2015, 03:03 AM

Hi Alec,

It doesn't necessarily need to be cold for dew to begin forming. The dew point is the magic number you need to keep an eye on. I shall attempt to explain below.

The dew point is the temperature below which moisture will condense out of the air and is dependent on relative humidity.

For example - say we get a warm winter night of 14 degrees.
If the relative humidity is quite high, say 70-80%, dew may start to form at around 10 degrees, so your telescope only has to become slightly cooler than the ambient air for dew to become a problem.

However, if it's a dry night around 40% relative humidity and 14 degrees, the dew point will be much lower and dew won't form until somewhere around 3 degrees perhaps.

These are just rough numbers but hopefully that made a bit of sense. It also depends where your telescope is located (ie out in the open or in an observatory etc.).

http://www.skippysky.com.au/Australia/ is generally what I use to look ahead and see if I may need to use the anti-dew equipment on any upcoming clear nights.
From memory the website suggests that if the dew risk gets below 5, it's likely you'll need to combat dew one way or another.
It's been pretty reliable so far for me.

I recently invested in a dew controller after losing way too many clear nights in recent months and I'd say it's definitely worthwhile having.
It's just one less way you can be prevented from enjoying a beautiful night under the stars.

I hope that helped. Feel free to PM me if you have any more questions

Cheers,
Bret

TV76 · #3 23-04-2015, 04:31 PM

Hi Bret,

Thanks very much for that and the link

...seems I need to do a bit reading around the topic and I may come back to you via PM.

As a matter of interest what make of Dew Controller and heating straps are you using?

Cheer,
Alec

britgc (Bret) · #4 23-04-2015, 05:19 PM

No worries at all Alec

I decided to go with a DewBuster controller and Kendrick premier straps.
Very happy with both items, especially the DewBuster.

All the best,

Bret

Stickboy (Phil) · #5 23-04-2015, 05:55 PM

Hi Bret you are using the Kendrick premier straps and not there controller. was there any reason for the two different brands

Phil

britgc (Bret) · #6 23-04-2015, 07:40 PM

Quote:

Originally Posted by Stickboy

Hi Bret you are using the Kendrick premier straps and not there controller. was there any reason for the two different brands

Phil

Hi Phil,

I was after a unit that offered temperature sensing but was still nice and simple to setup and operate for a newbie like myself, so it was between the DewBuster and the Digifire.

At the time I was considering which controller to get, Kendrick were in the process of updating their Digifire controllers and there were no details regarding what features the new models would have, only that they'd be similar to the current models with some improvements/new features.

The DewBuster won out fairly easily for my mind over the previous Digifire 10 model which is all I could really compare it to at the time.

Comparing it now with the Digifire 12 though, they are both pretty similar and I'd probably be doing some serious umm-ing and ahh-ing over which one to choose. The 8 volt DSLR power supply on the Digifire 12 would have been useful, but then I have a couple of batteries and I'd like to upgrade my camera soon anyway so

The DewBuster probably still fits my current needs and future plans better which is the main thing.
The main unit and accessories are also slightly cheaper than the Digifire 12 and its accessories.
It's quite small and just has the one dial to control the temperature delta, which is easy to use even with thick gloves on, plenty of additional heater outputs.
A 5 year warranty (compared to 1 year for the Digifire I think) is also pretty handy just in case, though judging by the build quality of the unit, I doubt I'll need it (touch wood

)

There's also a bit more customisation available with the DewBuster at the time of ordering which might be of use to some people.

I went with Kendrick Premier straps as they too have a good rep and apparently perform very well in quite cold conditions. Given that I intend on moving to NZ in the not too distant future, I felt that was the best way to go. They were also readily available locally in Australia.

I've probably forgotten something but I hope that helped in some way.

Cheers,
Bret

Stickboy (Phil) · #7 23-04-2015, 08:41 PM

Thanks Bret Great reply.

As you said its always hard buying something new as it may not suit your needs the way you were hoping. Kendrick now have the Digifire 12 and the soon to be released Premier Observatory Class Controller. In the end with temperature senses, number of ports and reliability they are all trying to do the same thing which might come down to the current draw of the controller on a deep cycle battery for a night of viewing

Phil

edit - DewBuster website has a very good write up of there product compared to Kendrick

britgc (Bret) · #8 23-04-2015, 11:01 PM

Quote:

Originally Posted by Stickboy

Thanks Bret Great reply.

As you said its always hard buying something new as it may not suit your needs the way you were hoping. Kendrick now have the Digifire 12 and the soon to be released Premier Observatory Class Controller. In the end with temperature senses, number of ports and reliability they are all trying to do the same thing which might come down to the current draw of the controller on a deep cycle battery for a night of viewing

Phil

edit - DewBuster website has a very good write up of there product compared to Kendrick

Agreed Phil.

I actually meant to mention that in my previous reply as it did play a role in my decision.

The other unit I read about which is similar to the Premier controller from Kendrick is the HitecAstro Mount Hub Pro.
Both these units are well beyond anything I need, but it may be an option for others.

The Mount Hub Pro 'Ultimate' is interesting...

TV76 · #9 24-04-2015, 10:59 PM

Hi Bret,

The 5 year warranty for the Dewbuster is very attractive given it has electrical components. I had been looking at the Dew Not controller as I had read some good reviews on their heater straps but the controller only has a 30-day warranty!!!

Alec

britgc (Bret) · #10 26-04-2015, 02:50 AM

Quote:

Originally Posted by TV76

Hi Bret,

The 5 year warranty for the Dewbuster is very attractive given it has electrical components. I had been looking at the Dew Not controller as I had read some good reviews on their heater straps but the controller only has a 30-day warranty!!!

Alec

Yeh, bit of difference there.

Not sure exactly where in Adelaide you're located but you're welcome to try my DewBuster unit out if you like. I'm pretty sure the Kendrick strap I have will just fit around your AP scope.

Perhaps in exchange for a glimpse of Jupiter/Saturn through that AP scope of yours? Or even just a glimpse of the scope itself?