Specifications

52 AUTOSTAR CCD PHOTOMETRY
LST Example
For 21 October 2005 at UT = 07h 10m 00s or 7.166667 hours.
Using the MICA printout shown in Table B-1, the Local Mean
Sidereal Time for 21 October 2005 for HPO (Phoenix , Arizona) at
Longitude = 112° 13m 22.0s West and Latitude 33° 30m 06.0s
North is 18h 29m 16.1843s or 18.487829 hours.
LST = 18.4897829 + 1.00274 * 7.1666667
LST = 25.674132 hours
Note: To test and adjust LST:
If (LST Lookup + UT * 1.00274) ≥ 24,
Use: (LST Lookup + UT * 1.00274) - 24
Otherwise, use: LST Lookup + UT * 1.00274.
Since the above value is greater than 24, 24 hours must be
subtracted from it to give:
LST = 1.674132 hours
Determining the Hour Angle (HA)
HA = LST – α
To determine the Observation's Hour Angle (HA), the observed
star's Right Ascension (α) is subtracted from the Local Sidereal
Time (LST).
For example:
Assume star α Aur:
RA = α = 5h 16m 41.3s or 5.278139 hours
Dec = δ = 45° 59m 53.0s or 45.998056 degrees
For LST = 1.674132 hours:
HA= 1.674132 – 5.278139
HA = –3.604007 hours
To convert HA from hours to degrees:
HA = –3.604007 * 15 degrees
HA = –54.060105 degrees