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

2" eyepiece mod and coma correctors for binocular telescope

eyepieces dob
  • Please log in to reply
7 replies to this topic

#1 alr10

alr10

    Lift Off

  • -----
  • topic starter
  • Posts: 2
  • Joined: 11 Nov 2010
  • Loc: Pennsylvania

Posted 16 October 2019 - 06:32 PM

We are constructing a binocular telescope and the interpupillary distance we are planning on (currently 4") may not allow for the 2" TeleVue lenses we are considering (we need the barrel to be less than 50 mm).  Has anyone managed to modify 2" eyepieces in a binocular telescope focusing mechanism.  Also, how have you mounted coma corectors (Paracorrs) in that setup.

 

I'm not the technical person on this project so if I have left out info or if this is too vague, let me know and I will try to make it more clear.

-Al



#2 steveastrouk

steveastrouk

    Viking 1

  • *****
  • Vendors
  • Posts: 983
  • Joined: 01 Aug 2013
  • Loc: State College, Pa.

Posted 16 October 2019 - 06:44 PM

4" IPD ?

Its mathematically impossible to get closer than 50.8mm, and thats a theoretical limit, because it means ALL the eyepiece has to be 50.8mm along its whole length. 

 

That said, you may find this paper interesting

http://citeseerx.ist...p=rep1&type=pdf

 

Statistically, there are not that many adult humans below around 55mm IPD, and the median of the data is around 60mm IIRC.

 

There are other correctors than the P2, if your F-ratio is not too high, maybe the Baader might work ?

 

I am working on a project with a friend using two Baaders, and 1.25 eyepieces.


  • Augustus likes this

#3 m. allan noah

m. allan noah

    Apollo

  • *****
  • Posts: 1142
  • Joined: 14 Aug 2009
  • Loc: Virginia, USA

Posted 16 October 2019 - 07:30 PM

4" IPD? good for hammerhead sharks perhaps?

 

allan


  • noisejammer likes this

#4 TOMDEY

TOMDEY

    Aurora

  • *****
  • Posts: 4899
  • Joined: 10 Feb 2014
  • Loc: Springwater, NY

Posted 16 October 2019 - 07:31 PM

Yeah --- your wording is unclear... is it that you can't get the eyepieces (and associated Star Diagonals etc etc ) any closer IPD than 4 inches, without something bumping? I don't see how that forces the eyepieces to need tube ODs smaller than two inches, unless you want to go to smaller Star Diagonals... which would kinda defeat the entire purpose of going to two-inch eyepieces to begin with!

 

Related: From the literature: "The key results are that mean adult IPD is around 63 mm, the vast majority of adults have IPDs in the range 50–75 mm." I'm lucky that my IPD is 71+ mm, so that I can very comfortably view thru a pair of two-inchers... even the ~fat~ ones. For ~snake-eyes~ folks, two-inchers are depressingly unusable. Why don't you gingerly machine material off of your Star Diagonals? Certainly not for the faint of heart --- but we did stuff like that at work --- often, even with glass involved!   Tom

Attached Thumbnails

  • 152 IPD.jpg
  • 153 toms eyes home optometry.jpg


#5 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 79448
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 16 October 2019 - 07:38 PM

A 4 inch IPD?

 

I had seen Steve's paper before.  Even 3 inches is highly unusual..

 

Jon



#6 alr10

alr10

    Lift Off

  • -----
  • topic starter
  • Posts: 2
  • Joined: 11 Nov 2010
  • Loc: Pennsylvania

Posted 16 October 2019 - 08:28 PM

My mistake.  I should have said 2 inches or 55mm.  Thanks for the comments, corrections and suggestions.



#7 Mike Lockwood

Mike Lockwood

    Vendor, Lockwood Custom Optics

  • *****
  • Vendors
  • Posts: 1643
  • Joined: 01 Oct 2007
  • Loc: Usually in my optical shop

Posted 16 October 2019 - 08:53 PM

Yes, he meant 2" IPD.  The Paracorr 2 lens groups are 2" OD, and thus their centers can be 2" apart themselves.  This would be a faster bino that requires them.

 

The question I have is this:  I have seen a large refracting binoscope that used clever machining of 2" focusers and eyepieces to allow those to be close enough together to have nearly a 2" (50mm) IPD.

 

Does anyone recall where that is or have a link?

 

Thanks for the help.


Edited by Mike Lockwood, 16 October 2019 - 08:58 PM.


#8 Oberon

Oberon

    Mercury-Atlas

  • -----
  • Posts: 2948
  • Joined: 24 Feb 2013
  • Loc: Hunter Valley NSW Australia

Posted 17 October 2019 - 05:55 AM

Sterope is designed (not yet built) to utilise 2” hardware, specifically the 17mm Ethos and Paracorr. While ordinary focusers are out of the question, a 55mm IPD is very doable once you abandon the ordinary practice of mounting the eyepieces in tubes.




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: eyepieces, dob



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics