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Making my own 5" binoscope

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#1 plyscope

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Posted 29 April 2016 - 07:36 AM

The inspiration for this project came from Mr Bill and his Bino Box thread from a couple of years ago. Thank you Bill for your advice and inspiration.

 

My version is compromised in that the IPD is fixed. This makes it possible to use only one mirror per side. I have used the same lenses as Bill, Istar 5" f5.5 achromats. There is a 1.52" minor axis diagonal mirror on one side and a 2.14" on the other with the lower lens. The focusers are Baader helical units with only a few millimeters of travel.

 

Initially I will be using 24mm Panoptic eyepieces and if I want to try different ones then they will need to be more or less parfocal. This will include most Tele Vue 1.25" eyepieces.

 

With the 24mm Panoptics the magnification is 29x. The exit pupil is 4.35mm. The field of view is 2.21 degrees. As you can see it is a work in progress and subject to change!

 

IMG_0786 - Copy.JPG

 

IMG_0787 - Copy.JPG

 

IMG_0788 - Copy.JPG


Edited by plyscope, 29 April 2016 - 08:11 AM.

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#2 plyscope

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Posted 29 April 2016 - 08:10 AM

Some more pictures.

 

IMG_0782 - Copy.JPG

 

IMG_0780 - Copy.JPG

 

IMG_0784 - Copy.JPG

 


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#3 junomike

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Posted 29 April 2016 - 08:15 AM

Wow, Looks Impressive!  What about viewing at Zenith?

 

Mike


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#4 plyscope

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Posted 29 April 2016 - 08:41 AM

Well I might make a tripod eventually. It is still at the proof of concept stage. It is about as simple as it gets for a large binocular.



#5 range88

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Posted 29 April 2016 - 09:38 AM

You'd better at least add a focusing mechanism...



#6 Alvin See

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Posted 29 April 2016 - 11:02 AM

You'd better at least add a focusing mechanism...

I see he has the Baader helical focuses.



#7 range88

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Posted 29 April 2016 - 11:26 AM


You'd better at least add a focusing mechanism...

I see he has the Baader helical focuses.

A few mm is hardly a focusing mechanism. Even diopter adjustment has more travel...

#8 Mr. Bill

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Posted 29 April 2016 - 11:31 AM

Excellent....I would suggest putting a partition between the light cones to eliminate any chance

of inter barrel off axis veiling glare when viewing bright objects.

How do you collimate with box closed?

The intra collimation can be accomplished with the objective cell push/pull screws.

Also, the 19mm Pans, DeLite eps, and 13mm Nagler are all parfocal so the 24mm Pans is a good choice.

How did you calculate the mirror sizes to optimize off axis illumination?

Edited by Mr. Bill, 29 April 2016 - 01:55 PM.

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#9 Mr. Bill

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Posted 29 April 2016 - 02:01 PM

You'd better at least add a focusing mechanism...

I see he has the Baader helical focuses.


A few mm is hardly a focusing mechanism. Even diopter adjustment has more travel...


Obviously not for star parties but great for the owner.

TV eps mentioned in my post above are parfocal within probably a mm so once focus is reached,

a few mms focusing travel is fine.
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#10 plyscope

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Posted 29 April 2016 - 04:10 PM

To answer your questions Bill;

There is a flat plate between the optical paths.

The diagonals can be adjusted with a 4mm Allen wrench using the bolts at the back. Each diagonal is mounted on an adjustable plate.

For the diagonal sizes, I drew the optical layout on paper and derived the sizes from the drawing. It is possible to have 100% illumination using bigger diagonals but I don't think that is required.

 

There will be further fiddling and fine tuning coming up and some paint too! The weather has been a bit cloudy lately. I want to use it and adjust it and prove to myself it is good to go.


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#11 Mark9473

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Posted 29 April 2016 - 04:26 PM

Looks excellent, Andy!


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#12 Erik Bakker

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Posted 06 May 2016 - 03:04 AM

Very nice bino Andy!


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#13 Gordon Rayner

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Posted 08 May 2016 - 01:51 PM

One wants the  two eyepieces'  eyecups' tops to  lie in the same horizontal plane,  at Zero  diopters, or , if one chooses,  in the same plane at   owner/principal  user/sole  user   personal diopter settings  at infinity.

 

Has  Istar   supplied  the lenses   with matching focal lengths?   Did you   specify  that, did they comply,  and was there  a premium  for that?    Do/did they   specify   a tolerance  for such matching?

 

What  mechanisms   have  you    to   space  the objective  cells   fore-aft,   to    compensate  for mismatched  focal lengths?   Thin washers,  with R&R  required  for each  adjustment iteration? 

 

Second  version Fuji 25 x 150  objectives,  and  those of the WW II  Zeiss  60 deg inclined 25 x 100,  and others,  have threaded  barrels  for fore-aft  adjustment.    At least some of the  US Navy Mk. 3  20 x 120  used  shims  there. 

 

  Katsuma   second-rate 7 x 50  near-copies  of B&L  WW II  Mk. 28  used thin shimming rings  there, along with   shimmed  prism  tilts held by grease,  and  large amounts  of brittle gray glue, Yuk!  Widely sold  by  various  importers.  Heavy and covered  with semi-useless heavy rubber "armor".



#14 Mr. Bill

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Posted 08 May 2016 - 06:34 PM

My focal lengths match within about 1/8 inch.....I used washers between one of the objective cells and BinoBox to bring the eyepiece heights equal (my eye diopters are the same.)


Edited by Mr. Bill, 08 May 2016 - 08:27 PM.


#15 MartinPond

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Posted 08 May 2016 - 07:26 PM

I love all the black open baffle-boxing inside.



#16 plyscope

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Posted 08 May 2016 - 08:28 PM

The lenses were purchased as a pair for a binocular and they have sequential serial numbers. There was no extra cost.

One of the lenses has a focal length of 700mm, the other is 713mm. This difference is taken up by an extra layer of plywood under the lens cell. In practice this difference in focal length does not seem to matter, at least not to my eyes. I have only been using it at 29x magnification with the 24mm Panoptics.

 

IMG_1044 - Copy.JPG

 

Thanks for all the positive feedback. I've been getting some good views with it and it works great. I can recommend this type of binocular for astronomy. It is a relatively easy ATM project once you have the optics. It is tempting to try and make a smaller version. Maybe I will try some aperture stops on this one first. It will be easy to try 100mm and 80mm stops.

 

 


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#17 Mr. Bill

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Posted 09 May 2016 - 09:04 AM

Looks like these have been deleted from the Istar website.

 

http://www.istar-opt...e-lenses-i.html



#18 range88

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Posted 09 May 2016 - 08:22 PM

Looks like these have been deleted from the Istar website.

http://www.istar-opt...e-lenses-i.html

These lens are made in China. You can still buy them via taobao.com, the corresponding model is 131/700. The focal length tolerance of Chinese national standard is +-5%, I don't know what Istar's standard is, but 713mm is probably still OK.

Edited by range88, 09 May 2016 - 08:22 PM.


#19 Fivemileshigh

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Posted 22 May 2016 - 09:01 AM

Very very nice and inspirational, thanks for posting this. I'm curious, how much does the OTA assembly weigh? (i.e. without the rocker box)

 

thanks


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#20 GlennLeDrew

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Posted 22 May 2016 - 09:16 AM

A 2% difference in objective f.l. is tolerable, which here is about 14mm. A difference of 4-5% is pushing matters, although the central region of the FOV would still be kind of OK. If an eyepiece pair could be found having the same ratio on their f.l., they could be matched to the appropriate objective.



#21 plyscope

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Posted 23 May 2016 - 01:11 AM

The OTA assembly is just under 10kg with 2 eyepieces.

 

Glenn the focal length difference does not seem to be a problem at 29x. I guess it could become more problematic at higher mags?



#22 Kunama

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Posted 23 May 2016 - 02:46 AM

Makes me wish I had kept the other TOA130 as well.   Nice work Andy !! 


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#23 GlennLeDrew

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Posted 23 May 2016 - 04:40 AM

Andy,
No matter the magnification, a given objective focal difference results in the identical image scale difference at given *apparent* angular distance off axis.

What matters instead is AFoV. The larger the AFoV, the greater the divergence in radial distance for an object at the field edge. To illustrate, suppose that for a 50 degree AFoV eyepiece an object is at the very field edge in one eyepiece, and in the other eyepiece it's inside the field edge by an *apparent* angle of 1/2 degree. (This would be the same whether the magnification is low, medium or high.) Switching to a 100 degree AFoV eyepiece pair would, when in one the object is at the field edge, have the other object 1degrea full degree inward from the edge. (For 25 degree AFoV eyepieces, the radial difference would be 1/4 degree; for 150 degree AFoV eyepieces, 1.5 degrees, and so on.)

From the foregoing it's obvious, of course, that a difference in image scale becomes ever more impactful at increasing apparent angle off axis. If the image scale ratio is twice as bad, the field diameter in which the effect is not significant is half as large.

And again, to be absolutely certain there is no confusion, magnification has no bearing at all; apparent field angle alone is the determinant.


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#24 Mr. Bill

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Posted 23 May 2016 - 10:21 AM

Guess I lucked out....my Istar objectives are within 3-4mm.
 
I also asked for matching focal lengths and the lens cells are marked #9 and #10.

 

Since I asked for matched focal lengths,  I assume they matched lens sets before mounting in cells.

Attached Thumbnails

  • first light.JPG

Edited by Mr. Bill, 23 May 2016 - 05:18 PM.

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#25 daniel_h

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Posted 23 May 2016 - 10:21 PM

 

These lens are made in China. You can still buy them via taobao.com, the corresponding model is 131/700. The focal length tolerance of Chinese national standard is +-5%, I don't know what Istar's standard is, but 713mm is probably still OK.

 

i tried searching but couldn'd find their range of objectives




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