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Dew heater strap on C8 with Losmandy Dovetails

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#1 t-ara-fan

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Posted 11 January 2019 - 03:26 PM

I have an EdgeHD8 with two Losmandy DC8 Dovetails on risers.   (top for guide scope, bottom to attach to mount)

 

The risers are quite close to the corrector plate, and get in the way of wrapping my Kendrick dew heater strap around the scope.  The dew heater is too far forward, because the risers are in just the right spot. 

 

Has anyone dealt with this? Maybe put the strap further from the corrector, behind the riser bars? Maybe use one strap in front, and one behind? 

 

Related question:  I have a dew shield, that I hacked with a knife to get it to fit around the 2 riser bars.  And I put the dew strap outside the dew shield. That doesn't sound optimal from a thermal perspective.  Is there a better way?    And now I use Hyperstar, it is quite a mess with the 2 wires going to the camera.  So I have not been attaching the dew shield. That probably makes the frost worse (?).


Edited by t-ara-fan, 11 January 2019 - 03:32 PM.


#2 Rustler46

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Posted 11 January 2019 - 03:59 PM

I have an EdgeHD8 with two Losmandy DC8 Dovetails on risers.   (top for guide scope, bottom to attach to mount)

 

The risers are quite close to the corrector plate, and get in the way of wrapping my Kendrick dew heater strap around the scope.  The dew heater is too far forward, because the risers are in just the right spot. 

 

Has anyone dealt with this? Maybe put the strap further from the corrector, behind the riser bars? Maybe use one strap in front, and one behind? 

 

Related question:  I have a dew shield, that I hacked with a knife to get it to fit around the 2 riser bars.  And I put the dew strap outside the dew shield. That doesn't sound optimal from a thermal perspective.  Is there a better way?    And now I use Hyperstar, it is quite a mess with the 2 wires going to the camera.  So I have not been attaching the dew shield. That probably makes the frost worse (?).

I have used two dew heater straps on a C-8 and a C-11 with Celestron brand upper and lower dovetails. These dovetails are attached to the front and rear telescope castings without risers. But there is enough space underneath to slide the dew heaters just behind the corrector casting. The dew heater strips used are a Dew-not and an Astrozap. The Astrozap strip is one that had been removed from a heated dew shield. This one is just the naked printed heater strip which is quite thin. The Dew-Not strips are bit thicker but can also be routed under the dovetails.

 

According to the DewBuster website, the best location for applying heat is on the tube behind the front casting. Here's a photo showing the C-8 with two heater strips installed as described:

C-8 with Dollond-00486.jpg

The telescope on top is a 200 year old Dollond achromat spyglass

 

I also had to cut out some sections of the plastic dew shield to fit around the dovetails (top and bottom). Be aware that if the cutouts have a sharp 90 degree corner, this will form a stress point where the plastic will eventually crack. I recommend these corner areas be modified so that there is a short curve at this location rather than the sharp corner. For this you can do something like the following:

  • Drill a small hole (~1/4 to 5/16 inch) where the corners will eventually be located.
  • If the cutout is already made with a sharp corner, then take a small round file and round out the sharp edge that is present.

Doing one of the above will prevent this stress point from developing a crack. The following photo shows the C-8 with heater strips and dew shield before it was relieved for the dovetails as described.

G-11 - C-8 Photo Rig.jpg


Edited by Rustler46, 11 January 2019 - 06:07 PM.

  • Starman27, roelb and t-ara-fan like this

#3 t-ara-fan

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Posted 12 January 2019 - 01:20 AM

Thanks for the info, and the link right to the info on the DewBuster website.



#4 Rustler46

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Posted 12 January 2019 - 03:15 AM

Thanks for the info, and the link right to the info on the DewBuster website.

That Dewbuster website has a wealth of useful information. It's worth spending time looking at all the advice offered. And Ron Keating makes a high quality product, well worth the purchase price.




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