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HomeworkQ & A

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Chapter 9Chapter 9

Meridian Transit Meridian Transit of the Sunof the Sun

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Objectives:

■ Determine the zone time of meridian transit of the sun by the

GHA Method.

■ Make a meridian-transit observation of the sun and compute latitude from the observation

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Practical Exercise:

Problem 1.

Follow the Student Manual for guidance

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2. When the sun crosses your meridian its azimuth is:

a. 90° or 270°

b. 45° or 225°

c. 180° or 360°

d. 60° or 240°

Ref.: ¶ 4

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3. When the sun crosses your meridian its LHA is:

a. 0°

b. 90°

c. 180°

d. 270°

Ref.: ¶ 4

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4. An advantage of using a meridian transit sight to obtain latitude is that this method requires:

a. use of a calculator.

b. use of tables.

c. plotting.

d. the maximum altitude of the sun.

Ref.: ¶ 4, 15, 17

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5. The mean sun:

a. usually agrees with the apparent sun.

b. never agrees with the apparent sun.

c. moves in an erratic motion.

d. moves in a constant motion.

Ref.: ¶ 7

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6. GHA of the Sun:

a. defines the position of the hour circle of the mean sun.

b. defines the position of the hour circle of the apparent sun.

c. can be converted to mean time by dividing by 15° per hour.

d. is measured from the lower branch of the Greenwich meridian to the apparent sun.

Ref.: ¶ 9

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7. Find the ZT of meridian transit for the following dates and Longitudes:

a. Lo 175° 46' W on March 29__________

b. Lo 116° 40' E on June 23 __________

c. Lo 147° 21' W on August 16__________

d. Lo 128° 36' E on December 5__________

ZT 11-47-41

ZT 12-15-26

ZT 11-53-30

ZT 12-16-11

Ref.: ¶ 10 - 11

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8. The sun's declination on June 21 is approximately:

a. 16.7° S

b. 23.4° S

c. 16.7° N

d. 23.4° N

Ref.: ¶ 16, Fig. 9-2

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9. You observe the sun at its maximum altitude, south of your position, and determine Ho is 65° 32', and declination is 20° 10' S. What is your latitude? _______

Solution: Observer is North of Sun Ho = 65°32'Co-Alt = 90° - Ho = 24°28'

Co-Alt = 24°28'N Dec = 20° 10'S (Co-Alt & Dec opposite

names, subtract)Lat = 04°18'N

Ref.: ¶ 18

4° 18'N

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10. On May 7 you observe the sun at its maximum altitude, north of your position, and determine Ho is 62° 41' at a corrected UT time of 21 - 56 - 07. What is your latitude? ________

10°16.9'S

Solution: Observer is South of SunAlmanac Excerpt (App. B) for 7 May

21 hr Dec 17°01.4'Nd(+) 0.7dcorr + 0.7'

Dec 17°02.1'N

Ho = 62°41'Co-Alt = 90° - Ho = 90° - 62°41'Co-Alt = 27°19.0'S (since observer south of sun)Dec = 17°02.1'N (Co-Alt & Dec opposite names,

subtract)Lat = 10°16.9'S

Ref.: ¶ 18

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11. On April 18 you are at approximately L 35°N and Lo 17°E. You take a series of sights on the lower limb of the sun around the time of LAN. Your HE is 10' and the sextant IC is +0.4'.

a. What is your best estimate of the time of LAN? __________

b. What is your Lat?   ____________

11-50-38 Lat = 35° 04.5'

Sight No. ZT hs    1 11-34-57 65° 24.4'    2 11-38-12 65° 27.9'    3 11-40-05 65° 31.3'    4 11-42-50 65° 36.3'    5 11-46-36 65° 38.0'    6 11-48-02 65° 39.1'    7 11-49-10 65° 39.4'    8 11-50-38 65° 39.5' 9 11-51-24 65° 39.2'    10 11-52-18 65° 39.0'    11 11-54-16 65° 38.9'    12 12-00-41 65° 33.9'    13 12-03-35 65° 29.5'    14 12-05-40 65° 24.3' 

Ref.: ¶ 18 -21

Click to view solution on MT Form

Click to view plot of hs vs. ZT

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Meridian Transit Meridian Transit of the Sunof the Sun

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