Hourly Airmass Table Generator

The table resulting from this interface is generated using software devised by Brian Casey, using Skycalc by John Thorstensen.

Please note that the airmass table is generated specifically for the Hartung-Boothroyd observatory and will not be valid at other locations!

Explanation of Table

The table generated when you press the above button will contain several columns:

Local: local standard or daylight time
UT: Universal Time (previously known as "Greenwich" time -- time on the Earth's prime meridian)
LMST: Local Mean Sidereal Time -- the coordinate of Right Ascension currently crossing the meridian of the sky
HA: Hour Angle -- the number of hours east or west between the sky's meridian and the object
secz: secant of Z, the zenith angle, otherwise known as the air mass -- this is approximately the number of equivalent air columns relative to the air column of the zenith. Objects near the horizon will have a high airmass, will be heavily extincted, and also have differential absorption due to heavy scattering of blue light.
par.angl.: the parallactic angle -- not generally needed -- this is an angle defined for an object in the sky given clockwise between the north vector at the object and the vector pointing towards the zenith.
SunAlt: Sun Altitude -- civil sunset occurs at -0.5 degrees, civil twilight (bright dusk) at -6 degrees, nautical twilight (stars appear but horizon is defined) at -12 degrees, and astronomical twilight (essentially dark) at -18 degrees.
MoonAlt: Moon Altitude -- where the moon is relative to the horizon

NOTE -- you must enter three digits for each declination and right ascension, including minutes and seconds of arc.

Star Name
Right Ascension (hh mm ss)
Declination (dd mm ss)
Epoch (yyyy)
Altitude of twilight sun (degrees)