BarrySimon615
scholastic sledgehammer
Reged: 03/01/04
Posts: 918
Loc: New Orleans, LA
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I know Ed Zarenski has listed some separations before as an aid in determining binocular field of view. I am including in this post a representation of Sagitarrius with separations between major stars (in degrees and fractions of a degree). I will also add similar pictures of Leo and Ursa Major. Other constellations by request.
Note- binocular field of view is often misleading. Not only is the edge quite soft in many of them. Some have turned out to be flat out wrong. Usually the field is over-reported, resulting in disappointment when actually used. Sometimes field is measured a certain way (typically right at the eye lens). Our eyes usually sit a bit further back from the eye lens of the eyepiece so we do not see as much field as what is specified. However sometimes there is just no justification for the overly zealous numbers they put on some binoculars. (My opinion, you may feel otherwise.) In any event, use these charts to see how your binoculars stack up.
Barry Simon
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BarrySimon615
scholastic sledgehammer
Reged: 03/01/04
Posts: 918
Loc: New Orleans, LA
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Leo with separations.
Barry Simon
Edited by BarrySimon615 (04/25/04 03:30 PM)
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BarrySimon615
scholastic sledgehammer
Reged: 03/01/04
Posts: 918
Loc: New Orleans, LA
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Ursa Major with separations.
Barry Simon
Edited by BarrySimon615 (04/25/04 03:31 PM)
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KennyJ
Reged: 04/27/03
Posts: 10142
Loc: Lancashire UK
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Barry,
Thanks for these.
A very useful set of readily -available and indisputable aids there.
I'll bet a few members will be a little surprised when they come to measure up the "true field" of their binos against the stated figure !
Clear skies , Kenny.
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Two eyes and a preference to use both
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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Thank you. These are great.
Tim
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lighttrap
Reged: 02/06/04
Posts: 3833
Loc: cloudy, foggy, humid NC, US
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Barry, those are fantastic. Thank you. I hope I'm not asking for too much, but do you, by chance, have Orion, Auriga and Hercules done up that way? Actually, Cygnus, Cassiopeia and Lyra would be interesting for the coming months, but I won't press my luck. Do you have software that does this? If so, what is it? Currently, I'm on a mission to see if there's any relevant software that is compatible with a PDA.
Thanks bunches,
Mike Swaim
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18" Starsplitter II f/4.5
8" Hardin Dob f/6
C5 workhorse mini SCT f/10 or f/6.3
70mm TV Ranger dual purpose birding/astro
77mm Leica Televid APO
16x70 Fujinons on UA Deluxe Mt.
12x50 Nikon SE
8x30 Nikon E2s
and many others
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BarrySimon615
scholastic sledgehammer
Reged: 03/01/04
Posts: 918
Loc: New Orleans, LA
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I use DeskTop Universe to generate the pictures. I then use the measuring tool to measure the separations and using a calculator change minutes to fractions of a degree. I add the labeling using my Olympus Camedia digital camera software. I convert to jPeg by cropping and copying to a master with a black screen. Really pretty straightforward.
Here is one more for now - Scorpius, more to follow
Barry Simon
Edited by BarrySimon615 (04/26/04 12:54 AM)
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sftonkin
sage
Reged: 02/25/04
Posts: 395
Loc: Kent, UK
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Mike,
Both the software I use on my PC (Guide) and my Palm (2Sky) will do it. In Guide, you right-click on the two objects, then hit "Ins" -- it gives the separation and PA. In 2Sky, you tap on each object, then on the name-box of the second, and it gives you the separation.
HTH
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Stephen
Hindsight: The only truly diffraction-limited system
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12565
Loc: Cumberland, R I , USA42N71.4W
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Those are great diagrams Barry,
I listed the measures I've used for a long time in this article published over on the CN reviews side. Listed you will find about 15 or so constellations with measures identified. Done in tabular form, the info you would need is there, but it's not in a nice graphic presentation like barry put together. Here's a link to that article.
How To Measure TFOV of Binoculars
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
Edited by EdZ (04/26/04 09:18 AM)
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Anonymous
Unregistered
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I am not sure if DeskTop Univerise is freeware or shareware, but HomePlanet is and it generates nice sky images as well if anyone is interested.
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BarrySimon615
scholastic sledgehammer
Reged: 03/01/04
Posts: 918
Loc: New Orleans, LA
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Here is Lyra with separations between the major stars.
Barry Simon
Edited by BarrySimon615 (04/26/04 09:49 AM)
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12565
Loc: Cumberland, R I , USA42N71.4W
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A link to this entire thread has now been added to the "Best Of" links so this info won't get lost in the future.
edz
--------------------
Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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BarrySimon615
scholastic sledgehammer
Reged: 03/01/04
Posts: 918
Loc: New Orleans, LA
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Here is another one - Cygnus.
Barry Simon
Edited by BarrySimon615 (04/26/04 11:10 AM)
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lighttrap
Reged: 02/06/04
Posts: 3833
Loc: cloudy, foggy, humid NC, US
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Thanks, again, Barry. That sounds like a good bit of work to go through just on our account. It's appreciated.
Stephen and Nightwatch, I'll look for those programs. I just got a Sony Clie' and am in the process of filling it up. I never thought I wanted a PDA, but now I'm wondering what took me so long to get one.
Mike Swaim
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18" Starsplitter II f/4.5
8" Hardin Dob f/6
C5 workhorse mini SCT f/10 or f/6.3
70mm TV Ranger dual purpose birding/astro
77mm Leica Televid APO
16x70 Fujinons on UA Deluxe Mt.
12x50 Nikon SE
8x30 Nikon E2s
and many others
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KennyJ
Reged: 04/27/03
Posts: 10142
Loc: Lancashire UK
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Now we have these wonderful measuring aids , perhaps we could all post in the ACTUAL True Fields of View of all our binoculars ?
Regards , Kenny.
--------------------
Two eyes and a preference to use both
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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nemo
sage
Reged: 06/09/03
Posts: 388
Loc: Eugene,Oregon
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Barry,
I am going to print these out for my own use. This I reckon is a prime example of the old adage (A picture is worth a thousand numbers)-smile. As usual great work Barry.
Dan
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"Humility is not thinking less of your self-it is about thinking of yourself less."
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BarrySimon615
scholastic sledgehammer
Reged: 03/01/04
Posts: 918
Loc: New Orleans, LA
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Thanks Dan!
Here is another one, Hercules!
Barry
Edited by BarrySimon615 (04/26/04 01:46 PM)
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Anonymous
Unregistered
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Quote:
Now we have these wonderful measuring aids , perhaps we could all post in the ACTUAL True Fields of View of all our binoculars ?
The two stars at the end of Ursa Major's handle are 6.66 degrees according to the diagram. They virtually *exactly* fit in the f.o.v. in my cheap Omcon 7x50s (Made in Japan, about 10-15 years old). I wasn't wearing glasses, so I can see the full field of view available. So:
Stated f.o.v: 6.8 degrees
Actual f.o.v.: approx. 6.66 degrees
So it's exaggerated by about 2%. Disappointing, but nowhere near as bad as Orion Ultraview 10x50s which are advertised at 6.5 degrees, and are actually closer to 6.0 degrees. I've never seen any binocs with actual f.o.v. or eye relief greater than the specs...it's always the same or less. If it were simply discrepancies in measurement, you'd expect that, (based purely on chance), the measured spec would be better than the stated spec about as often as it being less. It's simple: most binoc manufacturers intentionally exaggerate...lie.
I wish there was an international standard that binoc manufacturers could volontarily abide by, which would read something like:
"In compliance with the International ______ Standard, we guarantee that our binoculars comply with the stated field of view specifications to within +/- 2% and eye relief to within +/- 4%." or something similar.
When I have time I'll try to measure my 20x50s and 10x25s. I'm hoping others will post measurements...I'd love to see how they compare to the specs, and perhaps we could get to know which binoc manufacturers are generally the worst offenders at exaggerating f.o.v., and which are the most reliable.
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Anonymous
Unregistered
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The 22x100 obies were well known for NOT having a FOV that was close to the quoted specs. They were advertised as being 3.5 degrees, but really they are around 2.7 to 2.8 degrees. Kevin at bigbinoculars.com has changed the advertisement spec quote and I assume the FOV stamp on the binos as well. This discrepancy was made obvious to me when I looked at the 3 stars in Orion's belt. They span approx. 3 degrees and I could just barely have all 3 stars in my view.
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12565
Loc: Cumberland, R I , USA42N71.4W
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The 22x100 Obies are advertised as 2.8°. They do measure Tfov at 2.7°.
They are still stamped on the prism housing as 3.5°.
The Obie 20x80 Standard is advertised as 3.5°. it measures 3.2°
The Obie 15x70 is advertised as 4.3°. it measures 4.3°
The Celestron 25x100 is advertised as 3.0°. It measures 2.4°
the Fujinon FMT-SX 16x70 is advertised as 4.0° and measures exactly 4.0°
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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I know we, the CN binocular community, have already talked about the advertised FOV vs TFOV discrepancy in the past, but this is a huge blunder in my opinion. How (and more importantly why) does this happen? This could be considered false advertisement by some. What's your take on this EdZ?
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12565
Loc: Cumberland, R I , USA42N71.4W
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I think distributors should make every effort to show in their advertising the proper values. It's an easy number to put your fingers on. It is a significant number in the buying decision. It would appear some of the major distributors are already addressing the issue.
Personally, I haven't yet found a binocular with Afov that varies much from a standard 60° to 65°. The Pentax lines and many 8x42s and 10x50s can be much narrower.
I expect Tfov for any brand binocular to be no more than Afov64°/Magnification, regardless of advertising. The results I get are almost always in line with that expectation.
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: 10142
Loc: Lancashire UK
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Ed,
I think you're probably correct to expect most binoculars to fall within those parameters , but there are notable exceptions.
My Swift Audubon Kestrel 10 x 50 , for example , measures out at more or less a genuine 70 degrees AFOV.
I can only qualify this assertion by stating that my "square card tests" confirm a magnification very close to a genuine 10x magnification.
( i.e a 10 cm x 10 cm card viewed through one lens of the binocular from 30 feet appears equal in size to a 1m x 1m square viewed naked eye by the other eye at the same time )
AND I can certainly see beyond the parameters of the
1m x 1m square from 30 feet through the binoculars
( which computes to well over 65 degrees AFOV )
Of course , the QUALITY of image in these outer regions renders that "extra 0.4 or 0.5 degrees TFOV" practically useless in terms of "positive identification" , so going back to comments made by Barry and yourself , it is becoming more and more apparant ( no pun intended ! )
to me at least , that the "band" of 60 to 65 degrees AFOV probably represents the generally prefered , and most "user -friendly" "sweet spot" of binocular viewing.
This of course IF any given binocular in question actually provides such a TFOV.
As far as "moral" or previously well -intended suggestions for "legislative" issues go ,I might add that the
"more respectable" and / or "higher priced" manufacturers DO tend to be more accurate with their stated and stamped fields of view of binoculars than some, if not most, of the others.
Regards , Kenny.
--------------------
Two eyes and a preference to use both
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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sftonkin
sage
Reged: 02/25/04
Posts: 395
Loc: Kent, UK
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An exception, Ed, is the Swift Newport. It claims 8.2deg AFoV and, whilst I have yet to measure it precisely using stellar separation, the claim is not grossly excessive. The eyepieces are socking great things -- I imagine some sort of implementaion of an Erfle. However, because of the severe vignetting (no part of the exit pupil is fully illuminated), you can't see the whole FoV at once so, whilst the claim may technically be approximately true, it is functionally useless.
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Stephen
Hindsight: The only truly diffraction-limited system
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12565
Loc: Cumberland, R I , USA42N71.4W
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Stephen,
What magnification is this Swift.
edz
--------------------
Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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sftonkin
sage
Reged: 02/25/04
Posts: 395
Loc: Kent, UK
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EdZ wrote:
>What magnification is this Swift.
x10 (it's a 10x50)
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Stephen
Hindsight: The only truly diffraction-limited system
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12565
Loc: Cumberland, R I , USA42N71.4W
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wow, that is a wide one then, isn't it. 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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sftonkin
sage
Reged: 02/25/04
Posts: 395
Loc: Kent, UK
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EdZ wrote:
>wow, that is a wide one then, isn't it.
Indeed! If this cloud ever clears, I'll measure it properly.
--------------------
Stephen
Hindsight: The only truly diffraction-limited system
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