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127mm f/5.5 binocular

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#151 JKoelman

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Posted 23 September 2012 - 08:44 AM

My amazement is that someone (as far as I know) hasn't done this design commercially as it is very practicable and avoids a lot of the problems of the porro prism design.


These guys seem to be commercializing a 3 mirror design: http://www.astro-mec...elfernrohre.htm

#152 Rich V.

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Posted 23 September 2012 - 10:43 AM

Yes, that was also the approach used in the Astromeccanica/Borg binoscope reviewed by Milt Wilcox eight years ago.

Rich

#153 Mr. Bill

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Posted 23 September 2012 - 10:48 AM

Okay, back to your binobox. How is the chromatic aberration? I'm pretty sensitive to that with a telescope, but don't notice it much in my binos. Is it because of the lower magnifications involved?

I'm toying with the idea of using a pair of the 6" Istar f/5 objectives to make a binobox. I'm also concerned about field curvature in an f/5 objective. How is the field curvature in yours?


Good question...I have both the Istar 6 inch f/5 lens set (in a MonoBox design I did last year) and of course the 5 inch f/5.5 lens sets.

Not overly impressed with CA and field curvature in the 6 inch....the 5 inch lens sets are much better in both parameters. Stars are pinpoint using Panoptics out to 90% of edge of field in 5 inch.

Actually, my Celestron (Synta) 6 inch f/5 shows a much better image than the Istar 6 inch, so the Istar's shortcomings go beyond the laws of physics.

However, for magnifications under 75x, the 6 inch f/5 objectives would do a good job for scanning MW fields.

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#154 Mr. Bill

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Posted 23 September 2012 - 11:00 AM

Looks to me they just stack 2 inch diagonals. I have to wonder about vignetting even at f/7.

My design uses a 3.1 inch mirror as the first element and by careful raytracing gives over 70% edge of field illumination and of course full effective aperture.

My comment about this design not being commercially available really refered to a fully integrated binocular....not just hanging diagonals on two telescopes.

#155 GlennLeDrew

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Posted 23 September 2012 - 03:50 PM

I wondered also about the vignetting and potential aperture loss incurred by having to push the focuser drawtube farther inward along the optical path when additional diagonals are attached at the back end...

A system designed from the ground up will be better in these respects.

#156 SandyHouTex

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Posted 24 September 2012 - 10:07 AM

Thanks Mr. Bill. I think you may have saved me from a very expensive mistake with the 6" Istar.

And the 6" f/5 Celestron (Synta) you're talking about is the Newtonian right?

#157 Mr. Bill

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Posted 24 September 2012 - 10:33 AM

No....that would be comparing apples and oranges.

It's a two element achromat just like the Istar.

Here's a picture of the two comparing coatings.

Not meaning to discourage you....for binoculars I think the Istar 6 inch f/5 lens sets would be fine....I chose to use the 5 inch f/5.5 lens set for mine because of size/weight considerations.

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#158 SandyHouTex

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Posted 24 September 2012 - 10:59 AM

Okay then I'm wondering where are the Celestron/Synta lenses available. When I did a search, I just came up with the 6" f/5 Newt.

Thanks,

#159 Rich V.

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Posted 24 September 2012 - 11:15 AM

Rodger, here's the 6" f5 refractor:

Celestron Omni XLT 6" refractor

Don't see it available as an OTA only, though.

Rich

#160 Mr. Bill

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Posted 24 September 2012 - 11:17 AM

I think you would have to buy two OTAs. Might make an interesting project using their tubes.

You could shorten the tubes to accomodate the relay mirror.

Frankly, I would go with the Istars...just remember that no matter what, short focus achromats will never give you good high magnification images.

The most I use on the Celestron is a 10mm Ethos which yields 75x. After that, the image degrades rapidly.

Just noticed from Celestron ad copy that the lens is aspheric....that would account for superior spherical aberration correction.

#161 SandyHouTex

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Posted 24 September 2012 - 12:39 PM

Thanks for the link Rich. Yea, buying two telescopes at $829 is probably not in my future. I do like the concept of Mr. Bill's bino box though so I just need to decide what to put in it. It might just be the Istar 127mm lenses that he used.

#162 SandyHouTex

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Posted 24 September 2012 - 12:41 PM

I'm not really looking for high mags Mr. Bill. I do want a 4 to 5 mm. exit pupil though. So whatever I end up with I'll just have to pick the right eyepiece.

#163 Mr. Bill

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Posted 24 September 2012 - 01:00 PM

I use and highly recommend the 24mm and 19mm Panoptics.

:waytogo:

#164 Collimator

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Posted 24 September 2012 - 01:26 PM

Sorry, but I am new to this.
Can someone direct me to reviews of the Vixen 125mm binocular telescope.
I think there may be 8 different eyepiece sets.

My RFT made in the 1970s contains a very good coated 5 1/8 inch f/5 Jaegers achromat, which I asked them to select specially. I think it was a cemented doublet in Jaegers own cell. The clear aperture was 123mm.
It performed beautifully for many years in a custom telescope I had made.
The magnifications were 16x with a Kodak WW2 EWA coated eyepiece. Almost 5 degree field. 3 inch eyepiece holder.
20x with 32mm 2 inch Erfle.
35x with 18mm 75 degree eyepiece uncoated.
75x with 8mm Edmunds RKE which is a wonderful combination.
145x with 4.3mm Swift Ortho unfortunately found to be radioactive later.
At 145x this magnification was fully useful and reached mag. 13.1 in town.
So I presume there must be other reasons why using two of these 145x eyepieces would not give good results in a binocular telescope.
And 210x with a 3mm Clave eyepiece. This was a little too much but still usable.

#165 Mr. Bill

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Posted 29 December 2012 - 05:43 PM

Well, looks like the BinoBox will be featured in S&T this spring in Gary Seronik's Telescope Workshop column....

A picture from the "photoshoot."

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#166 Mark9473

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Posted 29 December 2012 - 06:05 PM

Congratulations Mr. Bill; looking forward to the article.

#167 GlennLeDrew

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Posted 29 December 2012 - 06:45 PM

Good on ya, mate! I look forward to reading this one.

#168 Mr. Bill

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Posted 03 January 2013 - 12:01 PM

According to Gary, looks like April S&T for article... that means it will appear at the end of Feb, beginning of March.

:cool:

#169 faackanders2

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Posted 05 January 2013 - 04:20 PM

Congrats! How is the view?

#170 Mr. Bill

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Posted 05 January 2013 - 04:30 PM

Right now, overcast, but on a good night my skies are green/blue. SQMs of 21.5 on best nights.

:cool:

#171 faackanders2

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Posted 05 January 2013 - 06:46 PM

Brandon,
Binocular viewing incurrs a *cost*? Quite the contrary; it affords a *gain*.

//cut//

Squinting with one eye is an unnecessary handicap to be avoided. That's how binoculars should be promoted!


Oh come on, there's huge premium for a binocular view, as we're all aware. To most people, that incremental pleasure from a binocular view cannot justify the significant additional expense and complexity. That's why most telescopes, even those intended to be only visual instruments, remain monocular.

Even in refractor vs newt vs SCT debates, there are quantitative comparison data and arguments. I've tried to logically justify a binocular view but the argument always seems to boil down to: two eyes are better than one.

Which is where I started when I posed my original question (and with apologies to Mr. Bill, the OP, for taking the thread down this path). I was hoping Glenn had a quantitative metric that captured the "sheer pleasure" of a binocular view, beyond the straightforward summation equations.


Joy is subjective (like why some like 100AFOV or not). Thos with large telesopes can get a taste with binoviewers, but this normally comes at the expense of higher power and less light to each eye. Small binoculars provide much wider TFOVs than telescopes. Large binos still provide wider FOV than binoviewers. They are complimentary, and don't need to be exclusive.

#172 EricP

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Posted 05 January 2013 - 10:22 PM

That's awesome news, Bill! Congrats on making your mark in S&T. Looking forward to the article.

#173 planetmalc

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Posted 10 January 2013 - 01:22 PM

Mr Bill's design raises an intriguing possibility. Instead of fixing the mount to the side of the box, attach it instead to the BOTTOM. This allows the instrument to swing through a 180-degree arc from horizon to horizon via the zenith. If the OG's are spaced around 9" apart and the 1.25" diagonals have a small footprint, then the two diagonal arms can ALWAYS be swung to a position whereby the observer (probably seated) can look horizontally into the eyepieces with his head upright, and only small sideways movements of the head are needed to cater for objects at various declinations. In essence, the observer's position is extremely comfortable and fixed (until a significant change in RA is required).

Get the cardboard, scissors and drawing pins out and prove it for yourself!

#174 GlennLeDrew

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Posted 10 January 2013 - 02:22 PM

I don't see this as possible at all... I take it you mean the bino is now oriented such that when pointed toward the horizon, one objective lies directly above the other, effectively having the instrument lying on what would currently be considered the side.

#175 Mr. Bill

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Posted 10 January 2013 - 02:45 PM

The alternate position for positioning the diagonals puts eps much closer to the altitude axis so the swing from horizon to zenith is minimized.

I tried both and prefer the diagonals and ep further back as I generally observe standing and don't like leaning over the binos...

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