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

2.3x Opera Glasses

  • Please log in to reply
17 replies to this topic

#1 saemark30

saemark30

    Apollo

  • -----
  • topic starter
  • Posts: 1468
  • Joined: 21 Feb 2012

Posted 29 May 2015 - 06:45 PM

There a a few threads describing a low powered opera glass, around 2.3x and with a very wide field of around 28 degrees.

What would it take to make a DIY version? If we used 50mm binocular lenses what is the ideal negative fl eyepiece design to minimize edge aberrations?



#2 GlennLeDrew

GlennLeDrew

    Voyager 1

  • *****
  • Posts: 14538
  • Joined: 17 Jun 2008
  • Loc: Ottawa, Ontario, Canada

Posted 29 May 2015 - 07:47 PM

In those wide angle opera glasses the objective lenses are of very fast f/ratio. Or to put it another way, they're designed so as to be quite oversized, with the entrance pupil occupying only a fraction of its area for any one image point. For example, a 2.3X40, when used by an observer whose irises are 7mm, work as 2.3X16.1. The 'extra' objective is there only so as to permit that wide field. The wider the objective, the wider the FOV; that's how a Galilean system works because the exit pupil is *inside* the instrument.

Furthermore, these objectives are of the meniscus form, which is better for such a wide FOV. A standard achromat bino objective is not so 'bent' into a meniscus, and may not be able to ever deliver such a large FOV. Or it would require a more sophisticated eyepiece design, at least (any again, if feasible.)

Lastly, the f/ratio determines the maximum possible AFoV. A faster objective, as seen through the eyepiece, presents as an angularly wider, out-of-focus 'window'. A bino's f/3.8 objective cannot achieve the same large AFoV as can these opera glass objectives which are nearer to f/2.

#3 rellimdarb

rellimdarb

    Lift Off

  • -----
  • Posts: 5
  • Joined: 09 Oct 2009

Posted 29 May 2015 - 09:44 PM

I made a pair using Nikon 2x auxillary telephoto lenses (TC-E2). I found one for $9 and another for $13 online. I mounted them in a pair of safety goggles from a chain Home Improvment store ($3). Since there is no focus mechanism, wear glasses if needed, which is why I mounted them in the safety goggles to fit over my glasses. Gives 2x with @ 22 degree field. The Nikons are tack sharp and the Milky Way in a dark sky is absolutely gorgeous. For @$25 you can't go wrong.

Brad  


  • JKoelman and Oberon like this

#4 Oberon

Oberon

    Surveyor 1

  • -----
  • Posts: 1951
  • Joined: 24 Feb 2013
  • Loc: Hunter Valley NSW Australia

Posted 29 May 2015 - 11:35 PM

Interesting.

I wonder how the 3x would compare?

http://www.amazon.co...s/dp/B00005218D


  • JKoelman likes this

#5 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 61337
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 30 May 2015 - 01:49 AM

Interesting.

I wonder how the 3x would compare?

http://www.amazon.co...s/dp/B00005218D

 

I don't know but I am going to find out how they work as Telescopes, I have both the 2x version and the 3x for my Nikon 4500...

 

Jon



#6 Oberon

Oberon

    Surveyor 1

  • -----
  • Posts: 1951
  • Joined: 24 Feb 2013
  • Loc: Hunter Valley NSW Australia

Posted 30 May 2015 - 04:56 AM

Well I've just ordered a pair of Nikon TC-E2 but paid a little more than Glenn ($19 & $29 respectively). There are a few alternatives out there, mostly cheaper 2 element options, the Nikon has 4 elements plus reputation so I went that way. I'll probably build them into goggles...I can just see myself walking around with them at night and getting a reputation as some kind of Sheev...

 

Attached Thumbnails

  • thumb-Sheev.jpg


#7 Pinbout

Pinbout

    Hubble

  • *****
  • Posts: 16181
  • Joined: 22 Feb 2010
  • Loc: uhmm...still in 2nd grade

Posted 30 May 2015 - 06:04 AM

http://blogs.c.yimg....mg_0?1230612636



#8 Oberon

Oberon

    Surveyor 1

  • -----
  • Posts: 1951
  • Joined: 24 Feb 2013
  • Loc: Hunter Valley NSW Australia

Posted 30 May 2015 - 07:23 AM

Nice.

 

Expand please?



#9 Pinbout

Pinbout

    Hubble

  • *****
  • Posts: 16181
  • Joined: 22 Feb 2010
  • Loc: uhmm...still in 2nd grade

Posted 30 May 2015 - 08:06 AM

I did a search and saw those don't know much more.



#10 JKoelman

JKoelman

    Viking 1

  • -----
  • Posts: 766
  • Joined: 15 May 2011
  • Loc: Bangalore, India

Posted 30 May 2015 - 09:05 AM

Interesting.

I wonder how the 3x would compare?

http://www.amazon.co...s/dp/B00005218D

 

The TC-E3 front diameter would imply an IPD exceeding 72 mm. But as a monocle it might be worth a try.



#11 rellimdarb

rellimdarb

    Lift Off

  • -----
  • Posts: 5
  • Joined: 09 Oct 2009

Posted 30 May 2015 - 09:18 AM

My 2X Binos

 

Brad

Attached Thumbnails

  • 2X Binos.jpg

  • mak17, JKoelman and Oberon like this

#12 Oberon

Oberon

    Surveyor 1

  • -----
  • Posts: 1951
  • Joined: 24 Feb 2013
  • Loc: Hunter Valley NSW Australia

Posted 30 May 2015 - 09:24 AM

Definitely Sheev territory!! :grin:



#13 JKoelman

JKoelman

    Viking 1

  • -----
  • Posts: 766
  • Joined: 15 May 2011
  • Loc: Bangalore, India

Posted 30 May 2015 - 10:29 AM

There a a few threads describing a low powered opera glass, around 2.3x and with a very wide field of around 28 degrees.

What would it take to make a DIY version? If we used 50mm binocular lenses what is the ideal negative fl eyepiece design to minimize edge aberrations?

 

As Glenn has stressed: the FOV for a Galilean increases with decreasing separation between eye and eyepiece. So... the ideal eyepieces would be negative power contact lenses. This would then lead to a device consisting of no more than two fast (positive meniscus) objectives mounted in front of your eyes... 

 

[edit] On second thought: I don't think contact lenses with sufficient negative strength are available... [/edit]


Edited by JKoelman, 30 May 2015 - 10:48 AM.


#14 JKoelman

JKoelman

    Viking 1

  • -----
  • Posts: 766
  • Joined: 15 May 2011
  • Loc: Bangalore, India

Posted 30 May 2015 - 10:35 AM

 

Interesting.

I wonder how the 3x would compare?

http://www.amazon.co...s/dp/B00005218D

 

I don't know but I am going to find out how they work as Telescopes, I have both the 2x version and the 3x for my Nikon 4500...

 

Jon

 

 

Keen to hear what FOV you can squeeze out of the 3x Nikon. Also, a bi-directional flashlight test would reveal the true magnification. 



#15 rellimdarb

rellimdarb

    Lift Off

  • -----
  • Posts: 5
  • Joined: 09 Oct 2009

Posted 30 May 2015 - 10:35 AM

My observing buddy calls them "Geekazoid" binoculars !


  • Pinbout likes this

#16 JKoelman

JKoelman

    Viking 1

  • -----
  • Posts: 766
  • Joined: 15 May 2011
  • Loc: Bangalore, India

Posted 30 May 2015 - 11:22 AM

I made a pair using Nikon 2x auxillary telephoto lenses (TC-E2). I found one for $9 and another for $13 online. I mounted them in a pair of safety goggles from a chain Home Improvment store ($3). Since there is no focus mechanism, wear glasses if needed, which is why I mounted them in the safety goggles to fit over my glasses. Gives 2x with @ 22 degree field. The Nikons are tack sharp and the Milky Way in a dark sky is absolutely gorgeous. For @$25 you can't go wrong.

Brad  

 

Very nice idea. And implemented as 'sky goggles' they look gorgeous. :-) Any idea how much more field-of-view you would get without glasses (positioning your eyes closer to the tube)?



#17 rellimdarb

rellimdarb

    Lift Off

  • -----
  • Posts: 5
  • Joined: 09 Oct 2009

Posted 30 May 2015 - 05:06 PM

No, I'm so near sighted I didn't even consider it. The closer, the larger the field of view so if you don't need the correction, the field should be a bit wider. 

 

I just held another aux tele lens I had " in my drawer" up to my eye to check, and it makes a considerable difference.......wish I didn't need the correction !

 

Brad



#18 saemark30

saemark30

    Apollo

  • -----
  • topic starter
  • Posts: 1468
  • Joined: 21 Feb 2012

Posted 02 June 2015 - 12:06 PM

Are the Nikon TC-E2 lenses coated?

How sharp are the stars in the field of view?

And what is the true field of view?

 

 




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.







Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics