I notice that some manufacturers list the FOV as ft @ 1000yds and others list it as degrees @ 1000 meters. Can anyone tell me how to convert these?
Umm, if they give FOV in degrees, you can get 5 degrees to 5x52=260ft roughly . 52 to 53. There is a formula for everything. See optics planet, some bins have data in both figures.
here is a random example
105 m/1.000 m 6°/315 ft./1000 yds. 6°
so you divide the ft FIGURE with 3 to get the meters FIGURE
also 91 m / 1000 m=5,2°
[QUOTE=nuttingd]I notice that some manufacturers list the FOV as ft @ 1000yds and others list it as degrees @ 1000 meters. Can anyone tell me how to convert these?[/QUOTE]
This is a mistake. FOV is an angle so you can measure it in degrees (not degrees @ 1000m !).
FOV appears in three ways:
1) "x" ft @ 1000 yds
2) "y" m @ 1000 m
3) "z" degrees
Here are mathematical forumulas. I hope you will find them clear enough. This is just simple "school" trigonometry.
To translate 3) to 2):
y = tan(z)*1000 (result in meters)
example: for 6 degrees you get y = tan(6 deg)*1000 = 105 [m]
FOV = 105m @ 1000m
To translate 3) to 1) :
y = tan(z)*1000*3 (result in feets)
example: for 7 degrees you get y = tan(7 deg)*1000*3 = 368 [ft]
FOV = 368ft @ 1000yds
To translate 1) to 3):
z = arctan(x/3000)
example: for 262ft@1000yds you get z = arctan(262/3000) = 5 [deg]
To translate 2) to 3):
z = arctan( y/1000 )
example: for 140m@1000m you get z = arctan(140/1000) = 8 [deg]
And to translate 2) to 1):
x = y*3
And here is a link to table of conversion (at the bottom of the page). I'm afraid it is in Polish only but hope you will find out what is what.
http://www.optyczne.pl/index.php?slownik=63
First column gives you degrees, second meters at 1000 m, third feets at 1000 yds.