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Mark9473
Carpal Tunnel
Reged: 07/21/05
Posts: 2703
Loc: 51°N 4°E
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Quote:
I'd like to be able to use the sheer light gathering power of the 100mm to see the faintest objects I can see and still be able to use them with a 4mm or 5mm exit pupil to see the brightest image possible. 24x100 for me is nebula hunting mode.
Something about this continued to bother me as I signed off last night. Knowing full well that light gathering power increases with objective diameter, how did I make myself believe that for viewing extended objects only the exit pupil counts, or at least is much more important than objective size?
I believe I can trace this back to a recent thread on this forum in which it was said, if I recall correctly, that objective diameter as such is not a meaningful binocular parameter, next to other parameters such as exit pupil, twilight factor, magnification. And so, unconsciously, at that time I must have made a mental note "to forget about objective diameter"...
At this moment, I am beginning to realize that there could be another reason why exit pupil cannot be a stand-alone parameter determining the visibility of faint extended objects. It's quite simple really: a larger binocular having the same exit pupil as a smaller one, also by default has a higher magnification! The laws of physics conspire against us separating these two parameters.
An observer with 5 mm eye pupils could in principle compare the performance of 14x70 and 14x100 binoculars because each would behave as an instrument with effectively 5 mm exit pupil, but again the laws of physics intervene because they reduce the effective diameter of the larger optic to 70 mm.
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Mark
Leica 8x20; Vixen 8x42; Swift 8.5x44, 10x50 and 20x80; TS 7x50; Orion 15x63
WO Megrez II 80 FD + Baader 90° T2 Amici
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Shneor
super member
Reged: 03/01/05
Posts: 121
Loc: Northern California
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You may have seen Apogee's binoculars with built-in filters that can be flipped into place internally - why not make a binocular with built-in barlows working the same way for variable power in a fixed-eyepiece setup?
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Shneor
22" f/4 Sayre Monocular+Tom O. Eq. Platform
Burgess 25x100 Binos+T&T Mount
Denkmeier Binoviewer
Assorted small telescopes, 90-114mm
13.1" Travel Telescope
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12601
Loc: Cumberland, R I , USA42N71.4W
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That would require some technical mastery of mechanics to build an assembly that would accomodate the need to be in the correct position behind the focal point.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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HfxObserver
professor emeritus
Reged: 11/12/04
Posts: 624
Loc: Waterloo ON, Canada
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Well said Mark 
The pupil would act as an aperature mask, I just wonder if the sky background would still be as bright, I'm thinking it wouldn't be.
-Chris
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Chris
7X50 Vixen,22X100 Antares
80mm William Optics Megrez II ED
Santel MK6
Borg 125SD f6 (Pentax/Oasis version)
Tak-Lapides
Pentax XW's 40,20,14,10,3.5 3.8XP, Speers 5-8, 30mm Widescan III
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12601
Loc: Cumberland, R I , USA42N71.4W
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When eye pupil masks down the exit pupil, resulting brightness would be as if the objective were at the effective aperture dictated by the masked pupil, not the full aperture creating the oversized exit pupil.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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KennyJ
Reged: 04/27/03
Posts: 10163
Loc: Lancashire UK
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< the oversized exit pupil >
Ed , I'm so pleased you mentioned " exit - pupil " in that post .
It's the first time it's been mentioned so far tonight :-)
Just thought I'd " chime in " with that one !
Regards , Kenny
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If everyone is thinking the same thing , no-one is thinking - General George S.Patton
Zeiss 7 x 42 BGAT
Captain's Helmsman 7 x 50
Nikon 10 x 42 Superior E
Swift Audubon Kestrel 10 x 50
Helios 15 x 70 Observation
Strathspey 20 x 90
Televue 76 APO
Zeiss 85 Diascope
Helios 102 f5 refractor
Various eyepieces barlows tripods mounts etc.
Panasonic Lumix DMC - TZ5 digital camera
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Mark9473
Carpal Tunnel
Reged: 07/21/05
Posts: 2703
Loc: 51°N 4°E
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Quote:
why not make a binocular with built-in barlows working the same way for variable power in a fixed-eyepiece setup?
This to me is the single most important reason for even considering that a worthy upgrade from my 20x80s could well be a refractor with a Denkmeier binoviewer with Powerswitch. It's the only practical way I've yet found to obtain variable power without having to exchange eyepieces, and having the potential of a top-quality wide AFOV as opposed to existing zoom eyepieces.
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Mark
Leica 8x20; Vixen 8x42; Swift 8.5x44, 10x50 and 20x80; TS 7x50; Orion 15x63
WO Megrez II 80 FD + Baader 90° T2 Amici
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pcad
Carpal Tunnel
Reged: 01/17/05
Posts: 1501
Loc: Connecticut
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Hey Kenny, I mention exit pupils too. Well, square exit pupils, but that doesn't matter, does it? In the prism/coating thread.
Peter
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Peter
Telescopes 25 - 318 mm
Binoculars 15 - 88 mm
Microscope 50x - 1000x
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KennyJ
Reged: 04/27/03
Posts: 10163
Loc: Lancashire UK
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< Hey Kenny, I mention exit pupils too. Well, square exit pupils, but that doesn't matter, does it? In the prism/coating thread. >
Actually Peter , it DOES matter .
I deliberately told a little white lie to see if anyone would pick up on it !
Plus , doing it that way gave me the rare satisfaction of stating something which was incorrect :-)
Regards , Kenny
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If everyone is thinking the same thing , no-one is thinking - General George S.Patton
Zeiss 7 x 42 BGAT
Captain's Helmsman 7 x 50
Nikon 10 x 42 Superior E
Swift Audubon Kestrel 10 x 50
Helios 15 x 70 Observation
Strathspey 20 x 90
Televue 76 APO
Zeiss 85 Diascope
Helios 102 f5 refractor
Various eyepieces barlows tripods mounts etc.
Panasonic Lumix DMC - TZ5 digital camera
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pcad
Carpal Tunnel
Reged: 01/17/05
Posts: 1501
Loc: Connecticut
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Kenny,
Bill suggests that square pupils found in fast BK7 binos may not matter to many people. Anyway, just teasing about square pupils not mattering. Give me round, fully illuminated exit pupils any day of the week.
Peter
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Peter
Telescopes 25 - 318 mm
Binoculars 15 - 88 mm
Microscope 50x - 1000x
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grbrown
professor emeritus
Reged: 07/09/05
Posts: 643
Loc: Ampthill, UK, 52:02N 0:30W
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Quote:
I have inoperable aperture fever, money in my pocket to purchase new binos, and a strange fascination with Google. All of this means I have some new links to share with the group regarding giant 100mm+ binos.
I'd specifically like to ask Kenny (or one of the other fine gents from across the drink) if he has ever heard of the "Monk" brand of binos which appear suspiciously similar to the Celestron Skymaster model.
Thanks for indulging me...
MikeG
I can confirm that Monk is a long established company here in the UK, also one of our 3 importers of Kunming binoculars (you manage with only one in the USA!).
Having recently indulged ourselves by buying a pair of 45degree 100mm Kunmings I suggest you go for broke and join us - the water's fine! 
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Graham
"one eye good, two eyes better...the more I look, the more I see"
BT100-45 degrees, plus 35,24,17,13,9mm Sieberts
15x80, 7x50 Steiners
12x50, 10x42, 8x20 Leica Trinovids
7x35 Minolta
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Glassthrower
Vendor - Galactic Stone & Ironworks
Reged: 04/07/05
Posts: 14703
Loc: Hurricane Alley
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Quote:
I can confirm that Monk is a long established company here in the UK, also one of our 3 importers of Kunming binoculars (you manage with only one in the USA!).
Having recently indulged ourselves by buying a pair of 45degree 100mm Kunmings I suggest you go for broke and join us - the water's fine!
Graham -
Thanks for the input. I was wondering whether the Parks were Chinese or Japanese. I guess now I know. They seem a bit pricey for a Chinese bino. I'd be curious to look through a pair and see how they compare to the Celestron 100mm and the Oberwerk 100mm.
I just got my new 25x100 Celestrons back from warranty replacement. They get first light tonight, and that may determine whether I am in the market for a better bino or not.
MikeG
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Michael Gilmer - Member of the Meteoritical Society & Collector of Falling Stars.
Galactic Stone & Ironworks - Buy/Sell/Trade Meteorites, Moon Rocks, Mars Rocks, & 35 different falls and types!
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