Angular Distance Between Stars

06122017, 12:15 PM
Post: #1




Angular Distance Between Stars
Given the right ascension (α) and declination (δ) of two stars of the same epoch (J2000.0 is the most current), the distance between the stars are:
d = acos( sin δ1 * sin δ2 + cos δ1 * cos δ2 * cos (α1 – α2) ) The distance is usually given in decimal degrees. Enter α in terms of hours, minutes, seconds (standard notation) and δ in terms of degrees, minutes, seconds (standard notation). HP Prime Program: ANGSTAR Code:
Example Distance between Regulus (A) in Leo and Sadalmelik in Aquarius: (data via Wikipedia) Regulus: α = 10h8m23.11s, δ = +11°58’01.95” Sadamelik: α = 22h5m47.03593s, δ = 0°19’11.4568” Distance: 168°20’05.1793” Source: Meeus, Jean. Astronomical Algorithms WilliamBell, Inc. Richmond, VA 1991. ISBN 0943396352 

05152019, 04:45 PM
Post: #2




RE: Angular Distance Between Stars
Replying to an old thread, but this is a good way to measure a lens's focal length, since the angle of view is known for the focal length and image size (i.e., Full Frame vs APSC)
Here is a good method: http://www.bobatkins.com/photography/tec...ength.html 

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