How wide is your hand?

Most people who have an interest in astronomy (or atmospheric phenomena) will know the usual tricks for measuring angles and distances in the sky. The general idea is that you hold your hand at arm's length and, using difference parts of your hand, held in different ways, get a reasonable measure.

But how accurate is this approach?

Robin Scagell, via a post on the SPA BB, aims to find out:

I would like to find out what is the average dimension of a hand span in degrees. It is often said that a full hand span at arm's length is 20°, but I would like to get some accurate figures on this. So I have checked the distances between several well-known stars in the early evening sky and would like people to go out and test it for themselves.
Have a look Robin's post for full details of the experiment.


Ian Musgrave said...

My hand, when held up in "stop sign" mode at arms length, is pretty much 6 degrees across. SPlayed out theya re roughly 25 deg across.

Tag said...

I've calibrated my handspan from thumb-to-pinky at ~21° using 7.5° binocular field of view.
I use the technique often, mostly daytime when looking for Venus or young crescent moons. Works like a charm and very reliable.