Astronomy Calculations

1. Suppose you are sailing in the Pacific on July 7 and observe Vega (RA = 18h35m, dec. = +39°) at the zenith. Your GMT clock reads 8:55 am. a) What is Vega’s HA? b) What is the local sidereal time? c) What is the RA of the Sun? d) What is the HA of the Sun? e) What is the local solar time? f) What is your longitude? g) What is your latitude? h) Look at a map; where are you?

2.Suppose you am observing from the Cerro Tololo Interamerican Observatory in Chile (CTIO; lat. 30°S, long. 71°W) on May 28. At 9:50 p.m. EST you observe a bright star crossing the meridian 59° above the southern horizon. a) What is the star’s declination? b) What is the GMT? c) What is your local solar time (not the time zone time)? d) What is the RA of the Sun? e) What is the local sidereal time? f) What is the star’s RA? g) Check a star map; what star is it?

3. If you observe a star to have a maximum altitude of 84° above the southern horizon and a minimum altitude that is 6° above the northern horizon, a) what is your latitude? b) what is the star’s declination?