Measuring FOV? (1 Viewer)

[bugbear]

Since my new-to-me Mirador scope isn't marked with this, I'd like to measure the FOV.

Mirador 22-47 x 75mm spotting scope, balance?

I just bought a cheap, old-ish cope from eBay, per thread title. (Slightly discoloured rubber sleeve at the objective end) Mounting on my heaviest photographic tripod (Manfrotto #144, #168 ballhead), the views into my garden are bright and sharp - I am well pleased. However, the tripod mount...

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Is this as simple as getting a helper to place a garden cane into the the ground at the left/right extremes of the field (at "some distance")

And then measuring the distance, and separation of the canes?

Or it there an obvious-in-hindsight complication?

BugBear

 

[bugbear]

OK, out into the garden, zoom to minimum (stated as 22x)

Turns out 2 canes weren't needed - the FOV at the end of my garden is still only a few feet, so I just looked at the marks and numbers on an old measuring stick held by my assistant.

My surveyor's tape is metric; so my FOV is 3'2" @ 32.1m (!!).

Converting into decimal imperial units, that's 3.166 feet at 35.1 yards, so (pro rata) 3.166 * (1000/35.1) = 90 feet.

90 feet at 1000 yards.

In metric; 0.96 meters @ 32.1, pro rata 0.96 * (1000/32.1) = 30 meters.

30 meters at 1000 meters.

BugBear

 

[bugbear]

30m @ 1000m is 1.7°

BugBear