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Anonymous
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I own Tasco 7x35's (stop laughing) that I have had since dirt was created. Never thought to point them up until recently. I know so little at present about what I'm doing that they seem OK to me. Problem is they are not tripod adaptable. So I started looking for new ones only to find that low power large aperture binoculars are as hard to find around here as a decent telescope. I am looking to spend under a hundred (why are you still laughing) because I don't really need them. Sears has Meade 9x63 (might be 62 can't remember) roof prism "Comet Chasers" for $99.99. Are these going to be an OK set for beginner purposes? Should I keep looking until I find a 7x50 pair (which is what I started out looking for)? My concern is the Meade's may be a little big for handheld use. Thanks in advance.
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12601
Loc: Cumberland, R I , USA42N71.4W
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Unless you live in an area with extremely dark skies, mag 6+, AND have very large eye pupils, 7x50s are not really a good choice. the very large exit pupils of 7x50s, in moderately bright skies will give washed out views. And if you eye pupil does not get any larger than 5mm you would effectively have reduced the aperture to 35mm.
same goes for the 9x63s, repeat above.
Of course you could be buying these just for the wide field of view. In any case, I'd be looking for something with a 5mm exit pupil. 8x40 or 8x42 or 10x50.
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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Anonymous
Unregistered
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See I told you I didn't know what I was doing! I got the 7x50 idea from "Night Watch" and another book I own. I went back and reread the section on binoculars. Both books appear to recommend 7x50's but also mention 10x50's as good choices. 10x50's I can find everywhere. thanks for the help.
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KennyJ
Reged: 04/27/03
Posts: 10163
Loc: Lancashire UK
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Like most things in life ,I suppose a 9 x 63 binocular has it's time and place.
The time is not for me , at 52 years of age , and the place is certainly not where I live , with so much light pollution
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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Anonymous
Unregistered
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I'm fortunate enough to live in a fairly rural area with no major cities but at 47 my eyes aren't what they were even a couple years ago. Glad I asked.
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edcannon
professor emeritus
Reged: 11/19/03
Posts: 679
Loc: Austin, Texas
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Quote:
Unless you live in an area with extremely dark skies, mag 6+, AND have very large
eye pupils, 7x50s are not really a good choice. the very large exit pupils of 7x50s,
in moderately bright skies will give washed out views. And if you eye pupil does
not get any larger than 5mm you would effectively have reduced the aperture to 35mm.
...
edz
I'd like to follow this a little farther, and I hope I can ask this question
well enough. Assume a person has 5mm maximum pupil dilation. Even though
the person's eyes cannot take in all of a 7mm exit pupil, isn't the image
seen still brighter than that in a 5mm exit pupil? If so, if the person can
observe under dark skies, might there still be some benefit from the larger
exit pupils, even if the person can't take them in completely? If so, we
might call binoculars with 6-7mm exit pupils "dark sky" binoculars. Of
course there are still the disadvantages of (generally) smaller field of
view and more weight (and cost).
Ed Cannon - Austin, Texas, USA
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Ed Cannon - Austin, Texas, USA
As of 23 August 2008 - Celestron Skymaster 12x60
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Anonymous
Unregistered
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The following considers only those binoculars with equal magnifications.
I think *all* light which enters the optical tube through the edge/side of the front objective lens exits through the edge/side of the exit pupil. There should not be any measurable difference between the two 5mm sections, even if one is only a piece from a larger image. There are advantages for the 7mm(5mm effective), but I don't think brightness is one of them.
I arrived at this conclusion by realizing that the exit pupil size in an optical tube is predictable and distinct; no light from the center of the objective escapes far away from the center of the exit pupil. And also by my understanding that in a large exit pupil light is spread evenly across the entire exit pupil.
I think this is how it works, but as you may have noticed from my posts, and I'm sure several members have noticed, I'm generally wrong 50% of the time. (Thankfully my answers aren't given to true/false question- they are derived, otherwise it would appear that I simply guess to find my answers  )
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Blair
Pooh-Bah
Reged: 05/07/03
Posts: 1163
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I'm 52 years old and I enjoy my 11X70mm and 8X56mm Oberwerk Binocs. With my 11X70mm Binocs I can see, on average, a 9.8 star in the Pleiades with direct vision and when mounted. It takes an unusual night of seeing for my 8X56mm binocs to see this same star with direct vision even if mounted. Weight wise there is not a large difference between the two. The Field of view is the key difference. The Hyades Cluster looks very nice in the 8X56mm where the Pleiades are better in the 11X70mm. Possibly, Edz is correct about the effective aperture I am seeing because of my age and the surrounding light pollution but I receive nice views from both of these binocs. I do not have the 15X70mm binocs for comparison to see if there is a difference nor can I afford to buy them at the moment but may buy them in the future just to see.
Edited by Blair (02/09/04 03:52 AM)
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12601
Loc: Cumberland, R I , USA42N71.4W
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Daniel, the assumption that brightness remains the same regardless of eye pupil is incorrect. To answer Ed Cannon's question and Daniel's response:
All the light entering the objective is delivered to the Focal plane. In this case from a 9x63 or 7x50 binocular, the exit pupil would be 7mm. But, if the pencil of light must enter the eye thru a 5mm eye pupil, then the light entering the eye is the same as that from an effective aperture that would be produced by the magnification in use and a 5mm exit pupil. A ray diagram will prove that since magnification in the binocular is held constant ( or any scope with an constant eyepiece) and the entrance pupil is reduced to 5mm, the rays projected back to the objective lens would be that of a smaller aperture.
The only advantage to be gained (other than field of view) from a 7mm exit pupil would be brightness of image. Light gatering is not gained, that is from objective size. If you cannot utilize the full exit pupil, you have lost your entire brightness advantage. You will however have a much larger area behind which it will be easier for your eyes to acquire the image. That's why 7mm exit pupils may often be recommended for nautical use. It's easier to keep the eyes pupil lined up behind an exit pupil larger than the eye.
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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Anonymous
Unregistered
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EdZ, I remember the thread about exit pupil/brightness, I was only considering the situation where a person's eye pupil is 5mm. It seems(to me) that that you've labled me ignorant(which I am) and don't read what I say very carefully. This is slightly irritating to me. Or maybe I'm just not good at explaining myself, but here's something from my message:
"...There should not be any measurable difference between the two 5mm sections..."
I learned from the exit pupil thread that the bigger your eyes effective eye pupil the brighter the image, and that's what I was considering here.
Edited by Daniel_Schwartz (02/09/04 12:02 PM)
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12601
Loc: Cumberland, R I , USA42N71.4W
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Could be maybe you were not clear at all. My intent was simply to give a clear explanation of the problem and the solution. Here's how I read yor response to Ed C.
"The following considers only those binoculars with equal magnifications."
The question was about comparing exit pupil of 7mm vs eye pupil of 5mm. This has nothing to do with binoculars of equal magnification. Can be any magnification. So magnification had no bearing to the discussion.
"I think *all* light which enters the optical tube through the edge/side of the front objective lens exits through the edge/side of the exit pupil."
In the case of eye pupil smaller than exit pupil, the light may exit, but it doesn't go into the eye. You seemed to be saying all the light exits. You were not clear that all the exiting light does not enter the eye.
"There should not be any measurable difference between the two 5mm sections, even if one is only a piece from a larger image."
Since we were comparing 7mm vs 5mm, this was totally confusing to me, as there were not two different 5mm sections to compare! here you must be talking about the 5mm section of the light entering the eye, the only 5mm section.
"There are advantages for the 7mm(5mm effective), but I don't think brightness is one of them."
You were on the right track here, but for the life of me I couldn't figure out how you got there.
"I arrived at this conclusion by realizing that the exit pupil size in an optical tube is predictable and distinct;"
This statement, although true, didn't support any conclusion.
"no light from the center of the objective escapes far away from the center of the exit pupil."
A great deal of light escapes as unusable beyond the outside diameter of the eye pupil, so this was very confusing. At this point you seemed to tripped.
"And also by my understanding that in a large exit pupil light is spread evenly across the entire exit pupil."
This doesn't say anything towards the condition of the lost light.
"I was only considering the situation where a person's eye pupil is 5mm."
As was I.
"...There should not be any measurable difference between the two 5mm sections..."
again, I couldn't find two equal sections to compare. this was confusing.
So maybe you did understand this. But I found your answer very confusing and it seemed to me you didn't understand it at all. I did not by any means label you.
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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Anonymous
Unregistered
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Thanks EdZ, I'll try to communicate more clearly.
_____________________________________
I looked over the messages more carefully, and I can see that I had no reason to be bothered at all. Sorry EdZ, I'm not very mature.
Edited by Daniel_Schwartz (02/09/04 05:49 PM)
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KennyJ
Reged: 04/27/03
Posts: 10163
Loc: Lancashire UK
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I just hope that no unsuspecting "first-time visitor" to this forum is unfortunate enough to chance upon clicking onto Ed's LAST post :-)
Not that anything Ed says is incorrect in any way, shape or form -- but even though I've been following this thread word for word since it's instigation , I had one hell of a job trying to figure who had said what and why -- Einstein only knows what an "outsider looking in" would make of it if taken out of context.
I am as guilty as the next person , in fact more often than most, of sometimes diving in TOO quickly with ill-thought out "brainstormers" , but at least I try to make it quite clear exactly WHAT I AM suggesting , even it that suggestion might be a load of friend :-)
Admittedly this Eye -Pupil / Exit -Pupil business is a more complex and debatable subject than is generally acknowledged.
Complex enough, that is, without unclear statements and / or explanations.
May I suggest there is a thin line between enthusiasm and impetuousness.
I'm pleased to read Daniel's promise to try to communicate a little more clearly.
No offence intended of course !
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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KennyJ
Reged: 04/27/03
Posts: 10163
Loc: Lancashire UK
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Sorry but I originally posted a message to this thread with this message number that was meant for the "Angel" thread about advice on hand -held binos.
As a result Erik's subsequent message ought to be re -located to that thread.
Regards , Kenny.
--------------------
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
Edited by KennyJ (02/10/04 02:35 AM)
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Erik D
Carpal Tunnel
Reged: 04/28/03
Posts: 2573
Loc: Central New Jersey, USA
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I think Kenny is referring to my recommendation for the Orion Scenix 10X50 WA(12mm ER) in a different 'angel' thread. Of course he is right. Although I don't need glass with my binos I find 15 mm more comfortable.
I have had a little more time to serach around for quality 10X50s since my last post. I'd change my recommenation to the Minolta Activa instead. This pair is water proof, fog proof, with 6.5 deg FOV and 18mm eye relief and carries a 25 year warranty. Street price of $139.95 is $50 higher but I think the features are well worth the price difference.
Erik D
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