exam2solutions

# exam2solutions - AST 3722C Spring 2008 Final – solutions...

This preview shows pages 1–2. Sign up to view the full content.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: AST 3722C - Spring 2008 Final – solutions • Part A. ◦ 1. You need to calculate declination δ first to do this problem. Using handout #5 you should find that δ = 16 ◦ 25 ′ 04 ′′ . Then you can use the formula for finding H , and you get H = 03 h 40 m 53 . 6 s . Since A is a western azimuth you should know that H must be positive. ◦ 2. 1 hour later in solar time = (1 / . 99727) hours of sidereal time. So just add that on to the H from problem 1. H = 04 h 41 m 03 . 4 s . ◦ 3. You need to find H first and then relate it to the H from problems 1 or 2. You should get that H = 05 h 03 m 09 . 8 s when a = 20 ◦ . That’s 1 hour, 22 minutes, 16.2 seconds of sidereal time later than the H in problem 1. That’s 1 hour, 22 minutes, 2.7 seconds of solar time. So the clock time is 10:52:03 pm . ◦ 4. This question asks at what time the next day has exactly 1 sidereal day passed? 24 hours of sidereal time is 23 hours, 56 minutes, 04 seconds of solar time, so the time has to be 10:48:07 pm . ◦ 5. H = LST − α , so α = LST − H . Get H from problem 1, so α = 06 h 29 m 37 . 4 s . ◦ 6. This happens when the Sun’s R.A. is 12 hours away from the object’s R.A. So α ⊙ = 18 h 29 m 37 . 4 s . Recall that on the winter solstice α ⊙ = 18 h . The Sun changes R.A. by (360 / 365 . 25) = 0 . 9856 ◦ per day, which is like 3 m 56 . 6 s of R.A. per day. So it gets to 18 h 29 m 37 . 4 s about 7 to 8 days after the winter solstice, which is about December 29 . (If you’re within a day or two of this that’s fine.) Alternate interpretation: Find when this object transits at midnight. In other words on what day is LST 06:29:37 at local time of 12:00 am? Let “tonight” be April 22. I tell you that LST is 10:10:31 at local time 9:30 pm tonight. So 2.5 hours later, when it’s 12 midnight, LST will be 10:10:31 +(2 . 5 / . 99727) = 12:40:56. Every 24-hour time interval later, LST will be later by (24 / . 99727) = 24 h 03 m 56 . 5 s . Similary, every 24-hour time interval earlier, LST will be earlier by 24 h 03 m 56 . 5 s . Or in other words, LST shifts backward by 3 m 56 . 5...
View Full Document

{[ snackBarMessage ]}

### Page1 / 4

exam2solutions - AST 3722C Spring 2008 Final – solutions...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online