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Angular Distance (was Re: (meteorobs) Plotting: Three Stooges Method)
>>>I know the rule of thumb about fist size being 10 degrees
>
>HMMMMmmm... I thought I heard FIVE degrees??? Lew, wasn't it
>YOU who told me that last year??
Not me, Steve! :) Seriously, 10o-per-fist has been my standard
for angular distances since I was a mere tyke-o-twelve. Maybe I
gave you some other "yardstick" for 5 degrees of arc - the head
of Aquila, the distance between Rasalhague and Rasalgethi, or
maybe the "open end" of the bowl of the Little Dipper?? I also
use "one finger per 2 degrees" to approximate if I'm in a hurry!
BTW, I agree that there is SOME variation from person to person
on the "fist rule": however, you only need a few yardsticks like
those above to "calibrate" this rule for your own arm and hand!
And the variation is less than you might think: strangely, the
length of a person's arm seems pretty well correlated with the
size of their fist. (No off-color comment on this one please!)
Here are some rough yardsticks, along with their angular sizes:
2 degrees
=========
"Short ends" of the parallelogram in Lyra
Long leg (Zeta and Gamma) of the "Y" in Aquarius
Beta and Gamma Arietis (the "fainter two")
4 degrees
=========
"Eyes" of Draco
"Long ends" of the parallelogram in Lyra
Hamal (Alpha) and Beta Arietis
5 degrees
=========
Western "edge" of the "W" in Cassiopeia
(See list above for other 5o yardsticks!)
7 degrees
=========
Northern "Arm" (Beta and Gamma) in Libra
Eastern "Wing" (Delta and Eta) in Aquila
"Baseline" (Delta and Alpha) in Cassiopeia
10 degrees
==========
Alpha and Beta Aquarii
"Open end" (Alpha and Delta) in the Bowl of the Big Dipper
"Tail" (Delta and Beta) in Leo
15 degrees
==========
Southern "horn" (Aldebaran and Zeta) in Taurus
Polaris to the bottom of the bowl (Eta) in the Little Dipper
20 degrees
==========
Diagonal of the "Great Square" in Pegasus
"Horn and snout" (Beta and Gamma) in Taurus
30 degrees
==========
"Snout to snout" (Phi and Iota) in Pisces
Alpha Ursae Majoris and Alpha (Polaris) Ursae Minoris
Would other folks care to share their own "handy yardsticks"? :)
Clear skies all!
Lew
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