Recognize a Star: Declination and Right Ascention
from Altitude and Azimuth

INPUT: Altitude and Azimuth of the star, Greenwich Mean Time (UT), location
OUTPUT: Declination, Right Ascention and SHA of the Star
(After that look a corresponding star in the Nautical Almanac or Skymap-program.
Then you can look exact declination and RA/LHA and calculate exact position.)

Altitude of Star          Azimuth from North clockwise
 Deg Min Sec       Deg  Min   Sec

Greenwich Mean Time (UT)
 Year  Month   Day   Hour  Min   Sec

Latitude and Longitude of the measurement location
Latitude:    Deg min sec
Longitude: Deg min sec

Click on Button:

The Declination, Right Ascention and LHA of the Star:
 Declination:    degrees minutes seconds
Right Ascention (RA) hours minutes seconds
Sidereal Hour Angle (SHA): degrees minutes seconds
(Nautical Almanacs use SHA, astronoms use RA)

Additional Information:
Julian Day at UT0:
Greenwich Mean Sidereal Time (GMST): hours minutes seconds
Local Sidereal Time (LST): hours minutes seconds
Local Hour Angle (LHA): hours minutes seconds
Greenwich Hour Angle (GHA): hours minutes seconds

Mathematical Background of Recognizing a Star by Altitude and Azimuth

Calculate Position from one star's azimuth and altitude
(Not so good as two star's altitude method, but
suitable for emergency situations when only one star is visible.)

Measure one star's altitude and azimuth, recognize star. Then look a corresponding star in the Nautical Almanac or Skymap-program. Then you can look exact declination and RA or LHA and calculate more exact position.

Latitude and Longitude using two star's altitude
(Good method, when you see many stars.)

Navigation, Astronavigation, Positioning, Geodesy




Juhani Kaukoranta, Raahen lukio, Finland
Email: juhani.kaukoranta@mail.suomi.net
Homepage: http://koti.mbnet.fi/jukaukor/
Last changes 2.6.2006