Thursday, September 25, 2008
determining sizes in the night sky
Some handy hints for judging the size (the angular size) of objects at a distance.
Useful for determining the size of an object or the distance between two objects.
I've coddled together various suggestions from many sources.
using one's hand:
- width of fist on outstretched arm is 10°
- width between thumb and little finger of outstretched hand is about 20°
- three fingers at arm's length are about 5°
- a fingertip at arm's length is about 1°
- tip of little finger is approx. ½°
comparing objects:
- the Sun and the Moon are ½° wide
- the Big Dipper is 25° wide
- the distance between the two pointer stars in the end of the Big Dipper is
about 5°
- the main part of Orion is about 20° tall and 10° wide
- the three rings in the Telrad bull's eye pattern are ½°, 2°,
and 4° in diameter
I hope to include more some visuals here shortly...
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