Week 2: WS3 #2

2. The Local Sidereal Time (LST) is the right ascension that is at the meridian right now. LST = 0:00 is at noon on the Vernal Equinox (the time when the Sun is on the meridian March 20th, for 2013 and 2014). 
a) What is the LST at midnight on the Vernal Equinox? 

Sidereal time is based on the time it takes for the Earth to complete exactly one rotation, rather than how long it takes for the same for the same point to realign with the Sun. As a result of the Earth's rotation around the Sun, these times differ slightly--LST picks up 4 minutes per day over "regular" time. Therefore, at midnight (12 hours after noon) on the Vernal Equinox, the LST would be 12:02.

b) What is the LST 24 hours later (after midnight in part 'a')? 

An extra 24 hours would mean an extra 4 minutes; 12:06.

c) What is the LST right now (to the nearest hour)? 

During our class time (2:30-4pm) on Tuesday, February 2, we calculated that the LST would be approximately 1:00--1 month and 18 days before the Vernal Equinox translates to a loss of about 3 hours. At 4pm, this would make the LST about 1:00.

d) What will the LST be tonight at midnight (to the nearest hour)? 

Approximately 8 hours after class time would make the LST about 9:00.

e) What LST will it be at sunset on your birthday? 

My birthday is July 27. If sunset is at 8pm, that makes this 4 months, 7 days, and 8 hours after noon on March 20th. This translates to a gain of 8:29 and an LST of 16:29.