Binoculars field of view in degrees

How would I find the field of view in degrees for a pair of binoculars given
the following info:
16x50 binoculars with eye relief of 10mm and exit pupil of 3.1mm. Terra
field of view is 182'@1000 yards.

Thanks. : )

FOV= (182*ft/3000*ft)*57.3=3.5 degrees

Jon

"riff" wrote in message
news:wzm7b.3259$pe.1704@lakeread06...
How would I find the field of view in degrees for a pair of binoculars
given
the following info:
16x50 binoculars with eye relief of 10mm and exit pupil of 3.1mm. Terra
field of view is 182'@1000 yards.


What's the problem? You've got all the information you need.

If the field is 182' at 3000', then the angle is (to an excellent
approximation:

182/3000 = 0.061 radians = 3.5 degrees

A rather small field of view, as you'd expect from an excessively high
magnification!

Regards,

Chris

"Chris Marriott" wrote in message
...

"riff" wrote in message
news:wzm7b.3259$pe.1704@lakeread06...
How would I find the field of view in degrees for a pair of binoculars
given
the following info:
16x50 binoculars with eye relief of 10mm and exit pupil of 3.1mm. Terra
field of view is 182'@1000 yards.


What's the problem? You've got all the information you need.


Well...now I do : )

If the field is 182' at 3000', then the angle is (to an excellent
approximation:

182/3000 = 0.061 radians = 3.5 degrees


Geez. Is that all I needed to do?

A rather small field of view, as you'd expect from an excessively high
magnification!

Thanks! Now I have "measured" proof of what I see and you're right. Small
field of view for constellations. Not bad for the moon though.

Thanks for helping an old fart out Chris. ; )

-Bob

"Jon Isaacs" wrote in message
...
How would I find the field of view in degrees for a pair of binoculars
given
the following info:
16x50 binoculars with eye relief of 10mm and exit pupil of 3.1mm. Terra
field of view is 182'@1000 yards.

Thanks. : )

FOV= (182*ft/3000*ft)*57.3=3.5 degrees

Jon

Thanks Jon

-Bob

"riff" wrote in message
newsun7b.3262$pe.3020@lakeread06...

"Chris Marriott" wrote in message
...

"riff" wrote in message
news:wzm7b.3259$pe.1704@lakeread06...
How would I find the field of view in degrees for a pair of binoculars
given
the following info:
16x50 binoculars with eye relief of 10mm and exit pupil of 3.1mm.
Terra
field of view is 182'@1000 yards.


What's the problem? You've got all the information you need.


Well...now I do : )

If the field is 182' at 3000', then the angle is (to an excellent
approximation:

182/3000 = 0.061 radians = 3.5 degrees


Geez. Is that all I needed to do?

A rather small field of view, as you'd expect from an excessively high
magnification!

Thanks! Now I have "measured" proof of what I see and you're right. Small
field of view for constellations. Not bad for the moon though.

Thanks for helping an old fart out Chris. ; )


Sorry, Bob; on reading my reply to you it sounds rather abrupt. It wasn't
intended to be that way; please excuse me!

Regards,

Chris

"Chris Marriott" wrote in message
...
snip
Sorry, Bob; on reading my reply to you it sounds rather abrupt. It
wasn't
intended to be that way; please excuse me!

Regards,

Chris


Heh. Thanks Chris. Actually, I know it must be frustrating for you and the
other very helpful and well informed guys in this group to answer the
obvious and perhaps simple questions. I'm just thankful for a resource like
this and for your taking the time to respond.

A follow-up if I may. Do you or anyone else know of a good site or internet
resource for _basic_ telescope optic formulas such as what you shared? I'm
a noob to this (quite obviously) and would be more interested in "less
academic/more lay-person friendly" sort of info. I did make use of Google
and found a few links but didn't know if anyone has a favorite or two. Many
thanks.

-Bob

"Jon Isaacs" wrote in message
...
How would I find the field of view in degrees for a pair of binoculars
given
the following info:
16x50 binoculars with eye relief of 10mm and exit pupil of 3.1mm. Terra
field of view is 182'@1000 yards.

Thanks. : )

FOV= (182*ft/3000*ft)*57.3=3.5 degrees

Further, apparent field is that times the magnification, or in this case 3.5
* 16 = 56 degrees.

Apparent field is about 50 for conventional binoculars, 60 or 70 for
wide-angle ones.

Conventional ones are sharper.

Bob, I wanted to summarized here some info I've collected on
binoculars so others could see:

Wide-angle binoculars can have narrow Afov eyepieces and Narrow angle
binoculars can have wide Afov eyepieces. Except at the narrowest and
widest extremes of True field of view, there is no standard rule you
can follow.

The way I have arranged these groups is based on personal use
preference. You may think otherwise, but my thoughts are after
hundreds of hours of use.

Most binoculars do not actually measure in the field what is stated
for Tfov. Usually the higher cost premium binoculars do measure as
stated.

Half of all binoculars I measured have Afov eyepieces between 60° and
65°. They cross a range from narrow to wide True field of view.
There are some but few wider eyepieces in use.

What may seem like a narrow 4° field of view would be wide for a 15x
or 16x binocular. A 3.5° field of view would be wide for a 20x
binocular.

On the other hand, a True field of view less than 3.0° is extremely
narrow for ANY binocular.

Some wide Afov eyepieces have excellent performance. Fujinon 16x70
and Oberwerk 15x70 use 64° Afov eyepieces and are sharp to 80%+ Tfov.
In comparison, Orion 16x80 uses a narrower 53° Afov eyepiece and its
sharpness characteristics are poor in the outer 40% Tfov.

Some of the newer 22x and 25x binoculars coming on the market are
advertised as 3.5° Tfov, but are measuring less than stated. If the
newer 22x an 25x binoculars measure over 3.0° Tfov, they are using
eyepieces with Afov approx. 66° to 75°, wider eyepieces than anything
I have seen to date.

The 8x binoculars with a 6.5° field of view may be considered the low
end of a wide True field of view for that power binocular. This Tfov
is not produced with a wide Afov eyepiece. They are sharp to 80% of
the True field of view.

edz


NARROW True Field of View
Pentax PCF V 20x60 Tfov 2.2 Afov 44
Pentax PCF V 16x60 Tfov 2.8 Afov 45
Orion Giant 16x80 Tfov 3.3 Afov 53
Oberwerk Deluxe 20x80 Tfov 3.3 Afov 65

STANDARD True Field of View
Fujinon FMT-SX 16x70 Tfov 4.0 Afov 64
Pentax PCF III 12x50 Tfov 4.2 Afov 50
Oberwerk 15x70 Tfov 4.3 Afov 64
Nikon S&E Kestrel 10x50 Tfov 4.9 Afov 49
Minolta Standard XL 12x50 Tfov 5.1 Afov 61

WIDE True Field of View
Orion Ultraview 10x50 Tfov 6.0 Afov 60
Orion Vista 8x42 Tfov 6.5 Afov 52
Swift Ultralite 8x42 Tfov 6.6 Afov 53
Minolta Standard XL 7x35 Tfov 9.0 Afov 63
Minolta Activa 7x35 Tfov 9.3 Afov 65


NARROW Apparent Field of View
Pentax PCF V 20x60 Tfov 2.2 Afov 44
Pentax PCF V 16x60 Tfov 2.8 Afov 45
Nikon S&E Kestrel 10x50 Tfov 4.9 Afov 49
Pentax PCF III 12x50 Tfov 4.2 Afov 50
Orion Vista 8x42 Tfov 6.5 Afov 52
Swift Ultralite 8x42 Tfov 6.6 Afov 53
Orion Giant 16x80 Tfov 3.3 Afov 53


WIDE Apparent Field of View
Orion Ultraview 10x50 Tfov 6.0 Afov 60
Minolta Standard XL 12x50 Tfov 5.1 Afov 61
Minolta Standard XL 7x35 Tfov 9.0 Afov 63
Fujinon FMT-SX 16x70 Tfov 4.0 Afov 64
Oberwerk 15x70 Tfov 4.3 Afov 64
Minolta Activa 7x35 Tfov 9.3 Afov 65
Oberwerk Deluxe 20x80 Tfov 3.3 Afov 65

"edz" wrote in message
om...
Bob, I wanted to summarized here some info I've collected on
binoculars so others could see:

Wide-angle binoculars can have narrow Afov eyepieces and Narrow angle
binoculars can have wide Afov eyepieces. Except at the narrowest and
widest extremes of True field of view, there is no standard rule you
can follow.

Not as I understand it. Binoculars are not called wide-angle unless the
field of view is wide *relative to their magnification*. That means wide
AFOV, always.

For example, 6x binoculars with a 7-degree field are not wide-angle, but 10x
binoculars with a 7-degree field definitely are wide-angle. The AFOVs are
42 and 70 degrees respectively.

Some cheap binoculars may be labeled "wide-angle" regardless of their field.

--
Clear skies,

Michael Covington -- www.covingtoninnovations.com
Author, Astrophotography for the Amateur
and (new) How to Use a Computerized Telescope

"edz" wrote in message
om...
"Michael A. Covington" wrote in message
...
Not as I understand it. Binoculars are not called wide-angle unless the
field of view is wide *relative to their magnification*. That means
wide
AFOV, always.

For example, 6x binoculars with a 7-degree field are not wide-angle, but
10x
binoculars with a 7-degree field definitely are wide-angle. The AFOVs
are
42 and 70 degrees respectively.

Some cheap binoculars may be labeled "wide-angle" regardless of their
field.

Hi Michael,

From practical experience I find binoculars over 6° Tfov are wide.

But standard 7x50 binoculars have a 7-degree field and are not labeled
"wide-angle". To the manufacturers and dealers, "wide-angle" means "a wider
angle than the usual binoculars of this magnification." In practice it
means "apparent field appreciably more than 50 degrees."

I'm not talking about whether it seems wide to you -- I'm talking about the
meaning of the term in product descriptions.

There are normal 7x binoculars and wide-angle 7x binoculars. Likewise there
are normal 12x binoculars and wide-angle 12x binoculars. The true field of
the wide-angle 12x may well be less than the true field of the ordinary 7x.