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HomeworkQ & A

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22

Objectives:

■ Obtain the GHA and declination of the sun from the Almanac

■ Use the GHA to calculate LHA

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1. Which of the following could be a reasonable value of GHA increment for the sun in approximately one-half hour?

a. 3°26.7'

b. 7°25.2'

c. 14°54.2'

d. 29°58.7'

Solution:The Sun travels westward at the rate of about I5°/hr or about 7.5° each half hour.Ref.: ¶ 13

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2. The d value at the bottom of the "Sun" column in the daily pages of the Nautical Almanac is:

a. always positive.

b. always negative.

c. positive or negative depending on the trend of the declination on the daily pages.

d. positive or negative depending on whether declination is North or South.

Ref.: ¶ 23

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3. The d value tabulated in the daily pages is:

a. the declination increment and always positive.

b. the average hourly change in the declination of a body.

c. the variable rate of change in GHA during one hour.

d. not used for the sun.

Ref.: ¶ 23

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4. You take a sight on the sun at 1447 UT. From the Nautical Almanac, you find that the Dec of the sun at 1400 UT is 5°42.7'N and at 1500 UT is 5° 41.7'N. The d value for the sun on that day is 0.9.

a. What is the sign of the d value for this sight?

b. What is the d correction?

c. What is the Dec of the sun at the time of the sight?

Ans: negative

Ans: -0.7’

Ans: 5°42.7' - 0.7'= 5°42.0'N

Ref.: ¶ 22 - 26

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5. Use Appendix B, Excerpts from the Nautical Almanac, and the "Increments and Corrections" table from any Nautical Almanac for the following. Find GHA, LHA, and DEC of the sun for each problem.

a. Sun LL; UT 09-32-12, 23 August; Lo 12°41.7'E.

b. Sun UL; UT 14-09-27,29 March; Lo 157°11.1'W.

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5a. Sun LL, UT 09-32-12, 23 Aug, Lo 12°41.7'E

LHA solution:09 hr 314°21.6' 32 min 12 sec 8°03.0' GHA 322°24.6' DR Lo(E) + 12°41.7' LHA 335°06.3'

Dec solution: 09 hr 11°21.7'Nd (-0.9')d corr(-) -0.5' Dec 11° 21.2'N

Ref.: ¶ 17 -- 27

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5b. Sun UL, UT 14-09-27, 29 Mar, Lo 157°11.1'W

LHA solution:14hr 28°49.1' 09 min 27 see 2°21.8' GHA 31°10.9'

+360° GHA 391°10.9'DR Lo(W) - 157°11.1' LHA 233°59.8'

Dec solution: 14 hr 3°33.7'Nd (+1.0')d corr(+) +0.2' Dec 3° 33.9'N

Ref.: ¶ 17 -- 27

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a. b. CommentBody Sun LL Sun UL; Daylight SavingsDate 24 Aug 2 Mar Time is in effectWE 3 sec fast 6 sec slowWT 16-09-58 09-38-37hs 38°24.8' 31°40.3'HE 8.0 ft 6.0 ft IE -9.4 +2.1 DR L 30°06.8'N 41°18.0'NDR Lo 85°43.6'W 73°06.8'W

Answers: LHA Dec Ho a. 51°12.8' 10°50.8'N

38°46.3' b. 323°31.7' 7°00.8'S 31°18.2'

6.For the following, complete all sections of a USPS SR96 Form to find the LHA, Dec, and Ho for each sight of the sun taken on a natural horizon. Use Appendix B, 'Excerpts from the Nautical Almanac', and the "Increments and Corrections" table from any Almanac.

Click to view Solution a.

Click to view Solution b.

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