Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Ritchey Chretien 8" tube Dew issue

cassegrain equipment reflector
  • Please log in to reply
2 replies to this topic

#1 gpowers1959

gpowers1959

    Lift Off

  • -----
  • topic starter
  • Posts: 2
  • Joined: 29 Jul 2020

Posted 01 December 2020 - 02:52 PM

Folks, I have acquired a new RC 8 and took it out for the first time a couple of nights ago. it was a bit cold and there was a lot of Dew gravitating towards my rig. I took a look down the tube on the RC 8 and the primary mirror was clear of Dew, however in seeing the reflection back to the secondary I could see that it was misting up badly. what effective solutions are out there to try and save the secondary from dew. I do have an Astrozap flexible dew shield on order,  ? - is this going to offer the protection needed on its own or are there other viable solutions out there i should be considering... cheers for any guidance.  Gary



#2 pyrasanth

pyrasanth

    Soyuz

  • *****
  • Posts: 3,531
  • Joined: 08 Jan 2016

Posted 01 December 2020 - 03:28 PM

I would get a heated dew strip and controller and put the band on the tube just behind the secondary mirror. This, along with the dew shield, will fix the issue. I find on damp nights I can't rely on the dew shield alone however with both the telescope can be dripping with dew & the corrector plate on my C14 remains clear.

 

The band will feel quite warm in the day but at night there will just enough heat to keep the OTA above the dew point- inside or out hence the mirrors will not mist up.


Edited by pyrasanth, 01 December 2020 - 03:32 PM.


#3 Nippon

Nippon

    Soyuz

  • *****
  • Posts: 3,855
  • Joined: 22 Oct 2009
  • Loc: Central Florida

Posted 01 December 2020 - 03:32 PM

I had the same issue with a Tak Mewlon 180. Primary would stay clear but secondary would dew up. I made a 6" long dew shield from an old flexible dew shield for a C8 and the secondary has not dewed up since. I just have to make sure the scope's cap is at the outside air temperature and close the tube up before bringing the scope inside. 


Edited by Nippon, 01 December 2020 - 03:38 PM.



CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics





Also tagged with one or more of these keywords: cassegrain, equipment, reflector



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics