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high performance Telrad dew heater from Russia

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#1 havasman

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Posted 20 June 2016 - 02:16 PM

Dew is a very big problem at the TAS dark site in Atoka County, Oklahoma. I really enjoy using the Telrad finder. Those two facts are not complementary. My Telrad use has become pretty much restricted to finding alignment objects to use in the narrow FOV crosshairs eyepiece to bring the Nexus DSC on-line well before dew sets in and for pointing toward the moon and brightest planets for a last peek when the session's over at teardown. That one usually involves looking through the fogged Telrad surfaces.

 

I have always had one of those plastic covers with the hinged flap on the objective end that's s'posed to be a dew shield. As you may know, it does @ 30% of what you need.

 

So I was interested to see the R-Sky guys had come to market with a dew heater for the Telrad. Nobody else I am aware of has had an active heater for it in years. When when they also developed a larger more powerful ep heater strip for the massive ep's on the market it was time to order.

 

The Telrad heater is shaped to fit around top of the reticle end of the Telrad and is retained by an elastic band with velcro on its end - very good fit and plenty secure. I was able to put it on and then install the plastic cover over it, retaining the cover with gaffers' tape (a.k.a. The Tape of the Gods).

 

I'd not plugged it in when setting up as I didn't know how the current draw of the robust ep heater that I did plug in would impact battery service life (hardly any as it turned out) but late in the session with everything wet with dew, I bent close to the scope and got a drop of water down the back of my t-shirt when it dripped off the Telrad. The unit was totally dewed over, wet on all surfaces and impossible to use for star hopping. Recognizing a good testing opportunity I plugged in the new heater.

 

After @ 20 minutes I checked back in to see what was up and found the optical path completely clear and the back of the plastic cover near the heater band FREE of moisture. My experience is that this thing works like a champ! As I use it - under the plastic dew shield - is probably optimal but by itself it would likely work fine if activated before dew set in and left running. Highly recommended 1st class product. The ep dew heater also works just fine. http://r-sky.org/en/

 

Telrad heater, small.JPG

 

In the pic the plastic shield is slightly raised to show the heater band in place, the cord is wrapped around the base and the RCA connector shows.


Edited by havasman, 20 June 2016 - 02:17 PM.


#2 Jeff Morgan

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Posted 20 June 2016 - 03:01 PM

Let me guess - made out of recycled titanium cooling water tubes from Chernobyl?



#3 havasman

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Posted 20 June 2016 - 03:15 PM

Let me guess - made out of recycled titanium cooling water tubes from Chernobyl?

It didn't glow in the dark!

 

Actually it seems very well built. It's sewn securely, has a good flexible cord with good connector for an RCA and the forming to fit a Telrad is spot-on.



#4 beatlejuice

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Posted 20 June 2016 - 05:02 PM

For the last couple of years I have used a hand warmer held to the side of the Telrad with an elastic band and it lasts for 4-5 hrs.

Even if it is already dewed up it will remove the dew in short order.

But then again I have a tendency to go low tech when it comes to dew. (except for portable hair dryer if I really get stuck)

 

Eric


Edited by beatlejuice, 20 June 2016 - 05:06 PM.


#5 GlennLeDrew

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Posted 20 June 2016 - 10:12 PM

I've simply epoxied a 150 Ohm, 1W resistor to the inside bottom of the window. It gets no simpler than that. At 12V it consumes just under 1 Watt of power, drawing less than 1/10 of an amp of current.



#6 R.bak

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Posted 21 June 2016 - 03:28 AM

Most nights, enough to install on the controller power is about 30%. Maximum current is 0,15A. That's not a lot.

Its 2 in1 -  Telrad dew heater and shield

 

Telrad_dew_heater_2_m.jpg


Edited by R.bak, 21 June 2016 - 09:59 AM.


#7 Sarkikos

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Posted 21 June 2016 - 09:14 PM

The Telrad heater is shaped to fit around top of the reticle end of the Telrad and is retained by an elastic band with velcro on its end - very good fit and plenty secure. I was able to put it on and then install the plastic cover over it, retaining the cover with gaffers' tape (a.k.a. The Tape of the Gods).

 

I'd not plugged it in when setting up as I didn't know how the current draw of the robust ep heater that I did plug in would impact battery service life (hardly any as it turned out) but late in the session with everything wet with dew, I bent close to the scope and got a drop of water down the back of my t-shirt when it dripped off the Telrad. The unit was totally dewed over, wet on all surfaces and impossible to use for star hopping. Recognizing a good testing opportunity I plugged in the new heater.

 

After @ 20 minutes I checked back in to see what was up and found the optical path completely clear and the back of the plastic cover near the heater band FREE of moisture. My experience is that this thing works like a champ! As I use it - under the plastic dew shield - is probably optimal but by itself it would likely work fine if activated before dew set in and left running. Highly recommended 1st class product. The ep dew heater also works just fine. http://r-sky.org/en/

 

attachicon.gifTelrad heater, small.JPG

 

In the pic the plastic shield is slightly raised to show the heater band in place, the cord is wrapped around the base and the RCA connector shows.

 

I recently bought one of the R-Sky Telrad heaters, too.  Unfortunately, I haven't had a chance to try it out at a dark site yet.

 

But why bother with the plastic dew shield?  The R-Sky strip by itself should be enough.  

 

I had a plastic hinged dew shield.  Mine even had a mirror in it.  But I never liked it.  Anything that you have to remember to fold up, fold down, fold up, fold down, gets old for me real fast.  I sold the thing long ago.

 

Mike



#8 Sarkikos

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Posted 21 June 2016 - 09:17 PM

I've simply epoxied a 150 Ohm, 1W resistor to the inside bottom of the window. It gets no simpler than that. At 12V it consumes just under 1 Watt of power, drawing less than 1/10 of an amp of current.

 

Sounds good, unless you really don't want to bother with resistors, soldering, splicing wire and rigging up batteries.  Not everyone is an electronics tinkerer.  I'd rather buy something someone has already made that works well.

 

Mike




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