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GlennLeDrew
Pooh-Bah
Reged: 06/18/08
Posts: 1269
Loc: Ottawa, Ontario, Canada
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Just finished putting them together in the 60mm aperture configuration yesterday, and gave them a good testing last night. Yippee! They work as well as could be hoped. I expect to have some photos posted before too long, so for now a verbal summary...
The components:
- Interchangeable objective barrels; 60mm f/4.5 and 50mm f/3.3 (the latter aspherized).
- 34mm clear aperture, coated, 90 degree Amici roof prisms from military surplus.
- Eyepieces; 2", 30mm Meade QX with 70 deg. AFoV and 13mm Ethos with 100 deg. AFoV.
- 2" Antares helical focusers with barrels cut down for lowest profile.
- Body is 3" square aluminum tubing with 1/8" wall thickness, cut to 6" length.
- Body and adapter rings are black anodized aluminum.
- Objective barrels are from 60mm refractor tubing (black painted).
- Objective cells are black ABS couplers, turned to fit on a lathe.
- a 3/8" thick 'foot' has a 1/4-20 hole for tripod mounting.
- Fixed IPD of 67mm, just for me. This was done for simplicity, cost-cutting and the sheer size of the focusers (66mm base width.)
- Estimated weight: about 5 pounds(?).
What remains to be made are the cover plates for the sides of the body (will use black plastic), as well as the barrels for the 50mm objectives.
The specs:
- With 50mm objectives and Ethos eyepieces; 12.7X, 7.7 deg. FOV, 3.9mm exit pupil.
- With 60mm objectives and 30mm eyepieces; 9X, 7.8 deg. FOV, 6.7mm exit pupil.
- With 60mm objectives and Ethos eyepieces; 20.8X, 4.7 deg. FOV, 2.9mm exit pupil.
Other details:
- The objective barrels are coated with a combination of flat black paint and sawdust. Blacker than the Hobbs of Hell!
- The precision build of the prisms allowed a simplified 'mounting' arrangement. In short, they're held in place simply with spring pressure, their lateral movement being constrained by a pair of protruding bolt heads.
- Collimation is via the same adapter ring which attaches the barrels. 2mm of 'slop' is built in, and the 3 bolts are used to align the entire barrel along with the objective.
Performance:
A significant advance over the Mk I. This is mainly due to the better eyepieces, not to mention the 'new' option of 60mm objectives (from a Russian 20x60). Needles to say, the highly corrected 13mm Ethos is a vast improvement over the former 15mm, 85 deg. AFoV bino eyepieces used 'til now. Where the older eyepiece had a 'sweet spot' of *maybe* 20% of the field diameter, the Ethos expands this to a good 50%. While this sounds not so great, recall that short focal length objectives have pretty wicked field curvature, which amply reveals itself when the eyepiece field stop is of any decently large diameter. Moreover, compare 20% of 85 deg. with 50% of 100 deg.
The 30mm Meade QX was a good choice for use with the 60mm f/4.5 objectives. It is of comparatively low cost, and offers noticeably better performance than the 30mm Knight Owl 80 deg. AFoV eyepieces I already have. While I do crave the widest possible AFoV, the combination of vignetting and slightly longer eye relief that a short focal length objective necessarily produces actually resulted in a reduced AFoV of little more than 70 degrees anyway. And the Meade's edge-of-field blur is about half that of the Knight Owl. Lastly, the Meade's sharply-imaged field stop circle is very much preferred to the more gradual edge-of-field fading seen in the other eyepiece.
As you're aware, a 9x60 is a lowest-power instrument, given its nearly 7mm exit pupil diameter. This results in the highest surface brightness of the image, which works well in darker skies as encountered out in the country. Narrow band filters can be used when searching for the larger, very low surface brightness nebulae.
The 21x60 configuration with the Ethos simply rules supreme! The spacewalk experience really is like pressing your face up to the porthole. The moderate exit pupil works well for brighter skies, such as I get from my apartment balcony. But I can't wait 'til I get out to our club's observatory! The nearly 3mm exit pupil is possibly the optimum when only one magnification must be used in deep sky observation.
I've already tried the Ethos with one of my aspheric 50mm objectives when I kludged up a crude tube assembly. So I already know it will work well as a 13x50, which I hope to have up and running soon.
I'm sure I can go on, but I'll finish for now. Me am happy!
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Home-made 11X50 right angle bino, 8.1 deg. FOV
Modified 26X100 bino, 3.5 deg. FOV
Home-made Mk II RA bino, using interchangeable objectives and eyepieces
My Gallery
Mediocre minds discuss people. Good minds discuss events. Great minds discuss ideas.
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KI4YUN
sage
Reged: 04/21/08
Posts: 490
Loc: Satsuma, Florida, USA
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Amazing. I have always admired your 50mm RA binocular. This seems like a great new invention you have on your hands.
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-Tristan
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daniel_h
sage
Reged: 03/08/08
Posts: 485
Loc: VIC, Australia
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do you have a link to some images?
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regal 10x42, 10x50ultras, 15x70 ultras, 20x80
Oly e-500, vixen 100/1000 with 0.965"/1.25",
2 old sturdy tripods for the bins (slik & velbon)
zeiss f5.6 refractor/lens (under construction)
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GlennLeDrew
Pooh-Bah
Reged: 06/18/08
Posts: 1269
Loc: Ottawa, Ontario, Canada
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I have yet to take photos, and when I do I'll post them in my Gallery here at CN and then provide a link from this thread. So stay tuned...
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Home-made 11X50 right angle bino, 8.1 deg. FOV
Modified 26X100 bino, 3.5 deg. FOV
Home-made Mk II RA bino, using interchangeable objectives and eyepieces
My Gallery
Mediocre minds discuss people. Good minds discuss events. Great minds discuss ideas.
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pcad
Carpal Tunnel
Reged: 01/17/05
Posts: 1767
Loc: Connecticut
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Sounds great Glenn! Looking forward to pictures and some observing reports.
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Peter
Telescopes 25 - 318 mm
Binoculars 15 - 88 mm
Microscope 50x - 1000x
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GlennLeDrew
Pooh-Bah
Reged: 06/18/08
Posts: 1269
Loc: Ottawa, Ontario, Canada
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Photos have been uploaded in my Gallery.
I had them out in darker skies at our club's observatory a few nights ago. I examined a wide range of objects in the 60mm aperture configuration, but using both the 13mm Ethos and Meade QX 30mm eyepieces, with and without UHC filters.
To be sure, the Ethos delivers the most spectacular view, what with its 100 deg. apparent field. For example, the entire Veil nebula (including the fainter 'Pickering's Triangular Wisp', located roughly in the middle) is nicely framed within the 21 power, 4.7 deg. field. In fact, a club member who was until then using the 16" newt exclaimed more than once that "This is what it's all about!"
For handheld scanning, the 9 power, nearly 8 deg. field delivered by the 30mm QX is quite enjoyable, too. The full figure of Lyra (i.e., the combined triangle and quadrilateral) just squeezes in. As a resolution test, I centered on 100 Herculis, an equal-brightness double separated by only 14 arcseconds. I have split it in a 10X50, and can now confirm 'splittability' at 9X. With the UHC filters in place, several of the brighter 'clumps' of the quite large gamma Cygni nebula complex (IC1318) are seen in one view.
Well, enough for the moment.
Cheers!
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Home-made 11X50 right angle bino, 8.1 deg. FOV
Modified 26X100 bino, 3.5 deg. FOV
Home-made Mk II RA bino, using interchangeable objectives and eyepieces
My Gallery
Mediocre minds discuss people. Good minds discuss events. Great minds discuss ideas.
Edited by GlennLeDrew (08/22/09 05:08 PM)
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pcad
Carpal Tunnel
Reged: 01/17/05
Posts: 1767
Loc: Connecticut
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Great pictures, thanks! I especially like the one that looks like you filled the objective tubes with dirt. 
Both the Mk1 and Mk2 make my attempt at a small RA binocular rather pathetic. At least I can appreciate how much fun these would be to use as well as being comfortable.
It would seem that you have experience and access to a machine shop. I wish I were able to put something like together on my own. Congratulations!
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Peter
Telescopes 25 - 318 mm
Binoculars 15 - 88 mm
Microscope 50x - 1000x
Edited by pcad (08/22/09 06:53 PM)
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Wes James
Post Laureate
Reged: 04/12/06
Posts: 3454
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Really awesome, Glenn- I envy you the ability to do things like this... would love to have a pair of these- I can only imagine what the views are like through them!
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Wes
Atlantic Beach, FL
Some bino’s from Miyauchi 5x32 Binon's up through Garrett 20x110 Signature's,
Some telescopes from a Stellarvue 80mm NHNG up through a couple of 8” reflectors…
And a wonderful 4.25" Delmarva Shiefspiegler!
Some good friends, made here on C/N.
Oh- several cats and a wonderful wife!
Anyone want a cat???? :-O
"When your work speaks for itself- Don't Interrupt" -Gamble Rogers
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Mark9473
Post Laureate
Reged: 07/21/05
Posts: 3211
Loc: 51°N 4°E
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I'm most impressed with your work, Glenn. Really awesome. I just came in from a 15x60 4.1° view - can only imagine what 21x60 4.7° would be like.
What do you suppose the specs would be like with a pair of Meade QX 20 mm or 26 mm eyepieces?
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Mark
Leica 8x20; Vixen 8x42; Swift 8.5x44, 10x50 and 20x80; TS 7x50; Orion 15x63; Docter 15x60
WO Megrez II 80 FD + Baader 90° T2 Amici
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GlennLeDrew
Pooh-Bah
Reged: 06/18/08
Posts: 1269
Loc: Ottawa, Ontario, Canada
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Mark,
I did briefly consider the 26mm QX instead of the settled-on 30mm. But I wanted an eyepiece that delivered:
- the largest *un-vignetted* field possible, and
- an exit pupil no larger than 7mm.
As to the 20mm and 26mm QX eyepieces if used with my 60mm f/4.5 objectives:
20mm -- 13.5X, 4.4mm exit pupil and 5.3 deg. TFoV.
26mm -- 10.4X, 5.8mm exit pupil and 6.8 deg. TFoV.
[and I have: 30mm -- 9X, 6.7mm exit pupil and 7.9 deg. TFoV.]
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Home-made 11X50 right angle bino, 8.1 deg. FOV
Modified 26X100 bino, 3.5 deg. FOV
Home-made Mk II RA bino, using interchangeable objectives and eyepieces
My Gallery
Mediocre minds discuss people. Good minds discuss events. Great minds discuss ideas.
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Photoner
sage
Reged: 12/06/06
Posts: 377
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I've noticed that finding a decent commercial 90° binocular is a frustrating task. So I can well understand why you would just haul-off and cook up your own set. But whole fabrication process just blows my mind. Thanks for sharing your mechano-optical wizardry. Meanwhile, I'm antsy about drilling a couple of holes in my dob UTA for a finder bracket!
Really enjoyed the bino pics and the whole gallery as well.
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Solar:40
Binoc:30x15IS,50x10,70x15,100x25
Refractor:60,72,80,90,102,120
SCT:125,200
Dob:317
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mercedes_sl1970
super member
Reged: 12/02/05
Posts: 144
Loc: Canberra, Oz
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I don't know - I think it's a fairly basic thing to make a set of binos with interchangeable barrels and eyepieces... I've made about 25 of them now - largest being a 203mm f8...
Yeah right!
Well done.
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GlennLeDrew
Pooh-Bah
Reged: 06/18/08
Posts: 1269
Loc: Ottawa, Ontario, Canada
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During the course of a couple of really clear nights earlier this week, I've enjoyed some extended observing sessions, revisiting many of my old favourites as well as some newer celestial acquaintances.
During Monday's slightly less transparent night I observed exclusively in the 21x60 configuration. Without filters, some of the subtler sights:
- The reflection component of nebula NGC6559, which is the visually brightest portion of the Sh2-29 complex (lying adjacent to and east of M8.) Note that this was past upper culmination and from Lat 45N--not far above the horizon!
- The large, curving arc of dark nebula B138, located in central Aquila. No need to star hop; just sweep the area and 'thar she be.' (No need to mention the literally *hundreds* of other dark nebulae splattered throught the many fields examined.)
With UHC filters installed, just a few of the more memorable sights:
- The eastern and brightest portion of the large elliptical emission shell surrounding the runaway star 68 Cygni, known as Sh2-119. Prior to this I'd seen it only in DougL's filtered 20x100 bino.
- The small emission nebula Sh2-113, located near Deneb.
- The Crescent nebula, NGC6888. Needless to say, at 21X it appeared only as an unresolved blob.
- Emission nebula Sh2-132, located not far from famous delta Cephei.
- The brightest portion of the large-ish Cave nebula, located within the Cepheus OB3 association and significantly dimmed by intervening dust clouds. This one is probably considered to be a challenge for 8-inch 'scopes.
Last night was among the best encountered at the observatory. Naked eye, M13 could be seen practicaly with direct vision, and the two 7th mag. stars in immediate attendance appeared as handle-like extensions. With the sky so nicely dark, I spent the night in 9x60 mode. While I generally do not prefer the largest exit pupils (6mm+), this was the kind of sky that warranted--and amply repaid--lowest power viewing!
During the first half of the night I cruised the milky way without filters installed. Even before the very nearly first quarter Moon had set, both halves of the Veil nebula were quite easily seen. The North America nebula was almost as obvious as the Bat Signal!
Once the Moon had well and truly sunk below the horizon it was dark nebula heaven. Barnard's 'E' was chiseled against the billowy star field, and its subtler SW extension spilled across a good fraction of the 7.9 deg field. The shaply defined western edge of the Scutum star cloud presented a 3-D-like view of nearby dust clouds suspended against a vastly more distant cloud of stars lying deep within the Galaxy. And what I call the 'Windsock', B168, was a stark, straight finger pointing toward the Lacerta OB1 association, from which come the stellar winds shaping it, its trailing end appearing as though fluttering in the breeze.
Later on I installed the Orion Ultrablock filters (akin to the Lumicon UHC.) Even at the comparatively low power of 9X, many subtle nebulae were revealed. Among them:
- Four of the brighter patches of the vast IC1318 complex surrounding gamma Cygni.
- The Pelican nebula, situated beside the North America Nebula.
- Most of the moderately reddened IC1396, located just south of Herschel's Garnet Star.
- In addition to the brighter shell segments of the Veil nebula, Pickering's Triangular Wisp, located roughly between.
- A hint of the aforementioned Sh2-119--really surprising!
- The large, really faint Sh2-157, located within the Cas OB2 association. No detail seen at this low power, though.
- The full extent of the Valentine nebula, IC1805, and the related IC1795/NGC896 blob. (Needless to say, the nearby, rather brighter Foetus nebula, IC1848, was extremely obvious by comparison.)
This is just a sample of the sights enjoyed, and comfortably, too, which allows to unhurriedly examine in detail. Based on the comments others have made, a wide angle of view has a profound impact (not that I needed reminding.) One of the club members with whom I shared many views said that he's becoming inspired to get back into binocular astronomy.
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Home-made 11X50 right angle bino, 8.1 deg. FOV
Modified 26X100 bino, 3.5 deg. FOV
Home-made Mk II RA bino, using interchangeable objectives and eyepieces
My Gallery
Mediocre minds discuss people. Good minds discuss events. Great minds discuss ideas.
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GlennLeDrew
Pooh-Bah
Reged: 06/18/08
Posts: 1269
Loc: Ottawa, Ontario, Canada
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A geometrical ray trace of the 60mm configuration, augmented by visual inspection, shows that with the 13mm Ethos the edge-of-field illumination is well over 90%. And even the 30mm QX, with its 37mm field stop being 3mm larger than the 34mm prism apertures, delivers over 50% llumnation at the edge. I forgot to determine the circle of full illumination, but would guess it to be around 20mm. (Recall that most commercial binos, due to their prisms' inability to fully accommodate the full on-axis cone of light, do not even offer full illumination at the very center of the field. I only half-joke when I say you could assign a *negative* value for their circles of full illumination!)
What contributes to the very good field illumination are the slightly-longer-than-normal, f/4.5 objectives and the use of large Amici prisms. An Amici has a shorter optical path length through glass than does a same-aperture Porro, thus yielding a larger circle of full illumination for a given prism-to-field stop separation.
I'll have to rig up a device with which to measure exit pupil brightness, so as to determine light throughput. My impression is that my bino passes a goodly fraction of the light passing through it, even though an Amici is potentially less efficient than a well-coated Porro. In fact I'd bet that image surface brightness is better than that deliverd by most lower end binos. (My 11x50 Mk I delivered a quite brighter exit pupil than did the original Bushnell 10x50 Xtra-Wide from whence came its objectives and eyepieces--I did a side-by-side comparison with another identical Bushnell.)
So I'm not surprised when others comment on how remarkably bright the image in my Mk II seems.
I have yet to cut the tubing for the 50mm objectives. I'm having so much fun with the 60's that I suppose the incentive is not there, yet.
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Home-made 11X50 right angle bino, 8.1 deg. FOV
Modified 26X100 bino, 3.5 deg. FOV
Home-made Mk II RA bino, using interchangeable objectives and eyepieces
My Gallery
Mediocre minds discuss people. Good minds discuss events. Great minds discuss ideas.
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Gordon Rayner
scholastic sledgehammer
Reged: 03/24/07
Posts: 965
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The Gallery photo of the prism mounting seems to show the Plexiglass bar pushing directly on one point of the roof. This would be a sure way to chip the roof at that point if the bar were metal. Is there a small groove in the Plexiglass, to distribute the load? Even if there is, that seems risky. Perhaps the Plexiglass has more local "give" than the prism glass.
How is the color error in your hybrid? Your description seems to indicate that, at least at f/4.5, the errors of the originally Porro prism-mated objective are also a good mate to the Amici, which is optically a thick glass block which adds its aberrations to the system.
I had aberration problems when attempting hybridization of Tele-Vue 65 deg. or so eyepieces to WW II f/3.5 Busch 10 x 80 with 45 deg. inclination.
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GlennLeDrew
Pooh-Bah
Reged: 06/18/08
Posts: 1269
Loc: Ottawa, Ontario, Canada
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Gordon,
The surplus Amici prisms I use have a shaped metal, protective 'shell' that stands *well* away from the prism's roof line. Moreover, the generally cylindrical shape of this perforated shell is quite strong. The spring force applied to the plexi bar is nowhere near enough to dent it! And I did file a bevel on the bar at the point of contact so as to better distribute the bearing force.
I wish I had another Tento 20x60 with which to compare color correction. It's been many years since looking through one, and so my memory is of doubtful value. At any rate, at 9X, with the 30mm QX eyepieces, I can see absolutely no false color on any target whatsoever. At 21X, with the 13mm Ethos, there is a small amount of chromatic aberration on the brighter subjects. It would seem that the big Amici works very like the original Porro, even though its optical path length is a bit smaller.
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Home-made 11X50 right angle bino, 8.1 deg. FOV
Modified 26X100 bino, 3.5 deg. FOV
Home-made Mk II RA bino, using interchangeable objectives and eyepieces
My Gallery
Mediocre minds discuss people. Good minds discuss events. Great minds discuss ideas.
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pcad
Carpal Tunnel
Reged: 01/17/05
Posts: 1767
Loc: Connecticut
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Considering that you're using more than $1000 worth of eyepieces for this project I have to assume that this was a spare no expense project. I was wondering if you thought about phase correction coating for the Amici roof prisms? I've never heard of this being available on other Amici prisms that are available. I don't even know if it's possible to put a phase correction coating on a roof prism as a consumer. Probably needs economies of scale to justify the cost.
I mention this since many people wouldn't buy an ordinary hi quality roof prism binocular without phase correction coatings. Leads me to think your RA binoculars could benefit from them too, if they were available. It's the only "feature" you don't have that is regularly found on binoculars.
Despite not having PC coatings, I have no doubt your 60mm RA Mk II probably outperforms any 60mm binocular I'm ever likely to get my hands on. That includes the Tak with its whopping 2.1° FOV. 
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Peter
Telescopes 25 - 318 mm
Binoculars 15 - 88 mm
Microscope 50x - 1000x
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GlennLeDrew
Pooh-Bah
Reged: 06/18/08
Posts: 1269
Loc: Ottawa, Ontario, Canada
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Peter,
This project wasn't a spare-no-expense, bust-open-the-piggybank affair. I had to keep some funds on hand for the next one, namely my 120mm RA bino (for which my current eyepiece pairs will perform signal service.)
I've already undertaken some prism transmission comparisons. I still have the original prisms from the Tento 20X60, and when I look through one of those Porro pairs alongside one of my Amicis, the latter delivers a rather less yellowish and brighter view. (I'll have to measure the transmission of those Russian prisms, which I'm astonished I haven't done yet!)
But I have measured the transmission of a few other Porro assemblies taken from '70's and '80's vintage binos whose prisms had been given the usual single-layer MgFl coating. I did this using a red LED laser working at a wavelength of about 638nm, which won't necessarily accord with transmission at the peak of visual response near 550nm. Transmission values were found to be between 89 to 92%. An uncoated, 21mm clear aperture Chinese-made Amici transmitted 89%. My military surplus, single-coating, 34mm clear aperture prisms also transmit 89%.
These comparative results did not lead me to consider having phase-correction coatings applied. Even if I could realize 98% throughput with the very best coatings, the additional gains over and above the current 89% would be a not-too-marked 10%, equivalent to 0.1 magnitude. (But of course this gain would apply to not just stars, but *everything* in the view. Which is why I state the following....)
In an instrument used for deep-sky work--and more so when the exit pupil is large, probably as important as absolute transmission efficiency is contrast retention via good baffling of stray light. Given the large-ish exit pupils I'm employing, the image surface brightness is reasonably high already, so I feel no pressing urge to bend every effort in order to pass *every* possible photon that hits the objectives.
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Home-made 11X50 right angle bino, 8.1 deg. FOV
Modified 26X100 bino, 3.5 deg. FOV
Home-made Mk II RA bino, using interchangeable objectives and eyepieces
My Gallery
Mediocre minds discuss people. Good minds discuss events. Great minds discuss ideas.
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pcad
Carpal Tunnel
Reged: 01/17/05
Posts: 1767
Loc: Connecticut
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Thanks Glenn. Glad to hear that there'll be larger RA binos in your future.
I asked about phase correction coatings partly because I've never heard of anyone offering a service that would add them to an existing roof prism. I've only seen PC coated roof prisms offered as part of a binocular, never as a stand alone item. Just curious.
I'm guessing that a monolithic Amici prism isn't what you'll use for a 120mm RA project. Keep us informed.
I like the idea of testing the transmission through various prism clusters. You mentioned using a red laser, and it's not being 550 nm. Would your test setup work with a green laser like a GLP?
I'm not sure a narrow beam laser shining through a roof prism will show the destructive interference that phase correction coatings are designed to minify. I'm not surprised that transmission through a roof prism would be equal to a Porro cluster if tested this way. It might even be better than a typical airspaced pair of Porro prisms due to having half as many air-glass interfaces. It would show the effects of anti-reflection coatings though.
Thanks for humoring me, I really do admire your handiwork.
--------------------
Peter
Telescopes 25 - 318 mm
Binoculars 15 - 88 mm
Microscope 50x - 1000x
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Wes James
Post Laureate
Reged: 04/12/06
Posts: 3454
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This is certainly an interesting discussion!
Wes
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