• Stacey

Dew or Dew Not?

Dew or dew not, there is no dry...well actually yes there is as long as you use some dew heaters on your telescope and imaging gear!

so i may have taken liberties with the movie quote :D

We take dew control pretty seriously here in the UK, so in this post i'm going to discuss a bit about what dew solutions I have been using up till now and what I will be using as we go forward from here.

I started imaging in earnest in January 2018, back then my setup was pretty basic compared to my imaging rig today. Back in January, it was very cold and I had no clue that I would even need dew heaters, but on more than one session I noticed that the quality of my subs were dropping as time went on. Finally I realized what was going on, my subs and my guiding was being wrecked by dew. Cue a rapid search for a solution to my dew problem..back then I settled on Hitec astro single channel dual port controller and a couple of heater straps from quite a well known company. Now these things aren't cheap, and when you pay a bit of money for something you kind of expect it to last for more than one season (which sadly for one of the straps, was not the case).

I have since discovered that not all dew straps are created equal. After my first dew strap failed, I decided to perform an autopsy. I found a flimsy strap material with the metal connections just crimped in and nearly coming out. I re-soldered these connections but alas it was no good, it ended up in the bin.

Dew strap

I have one other strap from the same company, and that one is still functional. Though it is a much smaller size so I suspect it was under less stress as it has been used. I wish I could say that the other strap failed due to overuse, but we all know what the weather is like here in the UK!

So fast forward to now in August 2019, the days are warm and humid but at night the temperature is starting to drop just a little, a perfect environment for dew. I've been thinking of what solutions I could go for, and mainly looking for a different dew strap manufacturer. It seems that most of the tapes i came across seemed to be very similar in design to the first one that had already failed, which obviously was a big negative to me.

Eventually I stumbled across "Dew Zapper" heaters, these instantly piqued my interest. Now before we go any further, these straps are more expensive (but not by much I found), but there are reasons for the extra cost...

A few specs on the Dew zapper tapes:

  1. High quality silicon cable with rubber outer sheath, glued to RCA jack for strain relief, remaining flexible at below zero temperatures, and moisture resistant.

  2. High-quality long lasting Nichrome wire heating element embedded in a fused flexible silicon substrate for moisture resistance and reliability. (NO "thin-film resistors" or "foil elements" are used!)

  3. Efficient with low power consumption. (Power consumption & heat output are determined by 12v controller power setting).

  4. Includes neoprene insulator on the back of the heater to direct heat inwards to the optics for better efficiency.

So if we take point one, a "high quality silicon cable"; why is this important to have? Well with some cables when temperature gets very low, the cables can become stiff and eventually fracture. Hopefully with a silicon cable this should not happen. Not only that but I like the way the RCA jack is covered in a rubber heat shrink type material. When I re-terminate cables at work, I always use rubber heat shrink as a strain relief.. I know this method works and so I was glad to see it listed on the specs.

Point two is also good, it is this thin film resistor that failed also on my previous dew strap. Even after I had re-soldered the tape and connections the dew strap refused to work...so I suspect it was the film resistors that had failed.

Point three and four is always a bonus, low power consumption and heating in an efficient way means that if you're running off a battery in a field, then you're going to get more time before those batteries go flat.

So basically these dew straps scream quality to me. I'm not the only one, comparing them with another strap a friend of mine also said the same.

Now these dew straps do have RCA jacks, so technically I could control them with my Hitec Astro dew controller, but it just so happens that I also purchased a Pegasus Astro Pocket Powerbox (PPB). This box of magic has two dew outputs (which is enough for me!) along with other things (which i shall cover in a future post).

Here it is all fitted to my scope:

Altair Astro 72EDF with Pegasus Pocket Powerbox fitted
Altair 72EDF with Pegasus Pocket Powerbox

Here's another image so you can see the new dew straps and how it all connects to the Pegasus Pocket Powerbox

Altair 72EDF with dew straps, pegasus pocket powerbox , hypercam 183C ProTEC
Dew Zapper Dew straps

Now you might be thinking "what is that small probe connected to the powerbox?"..... It's an environmental monitor. I shall cover this in more detail when I review the PPB, but for the purpose of this post it enables the PPB to measure the temperature and humidity of the environment it is in. For example, shortly before i took this picture it was telling me that the temperature in my lounge was 23 degrees with a relative humidity of 52%. It also gives the dew point and there is a handy feature called "auto dew" where it will turn the dew heaters on and off as needed. I am very impressed!

My overall thoughts are that even though the Dew Zapper tapes might be a bit more expensive than the other manufacturers, I would rather pay a little extra for something that is (hopefully) going to last.

I guess the old adage is true "buy cheap, buy twice".

Now all I need are some clear skies. Currently the UK is being battered by a bit of a crazy low depression which has caused a lot of rain, this means when the sky finally clears it will be very very damp out there. I can see me needing this brilliant dew setup sooner rather than later :)

Finally the important bit...where did I get my dew straps and PPB from?


Clear skies to all :)

#astronomy #astrophotography #amateurastronomy #stargazing #backyardastronomy #spacephotography #dewzapper #pegasusastro

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