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11. Plotting, And Advancing/Retarding the Assumed Position

11. Plotting, And Advancing/Retarding the Assumed Position. Presented By: Mate O. Course Outline. Navigational Astronomy Lecture 1 & 2 Mean Time / Apparent Time Lecture 3 Time Zones, Zone Description, Chronometer Time Lecture 4

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11. Plotting, And Advancing/Retarding the Assumed Position

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  1. 11. Plotting, And Advancing/Retarding the Assumed Position Presented By: Mate O

  2. Course Outline • Navigational Astronomy Lecture 1 & 2 • Mean Time / Apparent Time Lecture 3 • Time Zones, Zone Description, Chronometer Time Lecture 4 • The Earth, Celestial, And Horizon Coordinate System Lecture 5 & 6 • The Spherical Triangle Lecture 7 • Circle of Equal Altitude Intercept Lecture 8 • Time Diagram, Right Ascension Lecture 9 • The Nautical Almanac, Finding GHA, LHA, and Dec. Lecture 10 & 11 • Instruments For Celestial Navigation Lecture 12 • Sight Reduction of the Sun, Stars, Planets, Moon Lecture 13 - 15 • Plotting and Advancing / Retarding the Assumed Position Lecture 16 • Calculating Time of Meridian Passage (LAN) Lecture 17 • Calculating Latitude at Meridian Passage Lecture 18 • Calculating Time of Sunrise/ Sunset/ Twilight Lecture 19 • Star Shooting Schedule / Pub. 249 Lecture 20 • Azimuth and Amplitudes Lecture 21 – 24 • Polaris – Azimuth and Latitude By Lecture 25 • Star – Finder – Stars, Planets, Selecting the 3 best Stars Lecture 26 • The Complete Day’s Work Lecture 27 & 28

  3. Think of a Sight Reduction As Four Sections XI: Sight Reduction Sight Reduction Procedures Section #1 Body’s Name Index Correction Dip (Ht of Eye) Sum (Hs) Sextant Altitude (Ha) Apparent Altitude Altitude Correction Mars or Venus Addl. Additional Correction (T&B) Horizontal Parallax Correction Correction to Ha (Ho) Observed Altitude • (OR) • Body’s Name • Hs • (+ -) IC • Dip • Ha • (+ - ) Alt • (+ - ) Add’l • (+ - ) Add’l • Ho Moon

  4. GMT Time & Date XI: Sight Reduction Sight Reduction Procedures Section #2 Date DR Position L λ Observation Time (+ - ) Watch Error Zone Time ( + - ) Zone Description Greenwich Mean Time GMT Date

  5. Local Hour Angle and Declination XI: Sight Reduction Sight Reduction Procedures Section #3 GHA Hour GHA M&S “v” factor SHA GHA Total + or - 360° Assumed Longitude (-W, +E) Local Hour Angle Declination Hour “d” factor ( ) Declination Total Assumed Latitude

  6. Altitude Intercept and Azimuth XI: Sight Reduction Sight Reduction Procedures Section #4 Hc Tab (d) Interpolation Factor & (Dec. Inc) Double Second Difference Cor’n Hc Ho Altitude Intercept Azimuth Angle True Azimuth (Zn) From Section #1

  7. XI: Sight Reduction Sight Reduction Procedures Example: On May 16th, 1995 at 2011 – 26 ZT in DR Position L 39° 10 N, 157° 10’ W. The Star SPICA Was Observed at Hs of 32° 34.8’. The Index Error Was 2.1 off the Arc and Height of Eye 48 Feet III. IV. I. SPICA II. GHA M&S SHA GHA - λ Assum. LHA  Dec. S (d) Dec Assum. Lat 324° 28.4’ 2° 52.0’ 158° 45.3 486° 05.7’ 157° 05.7’ 329° 11° 08.4’ N.A. S 11° 08.4’ N 39° (Contrary) Hc Tab (“d” factor) (53.0) Dec. Inc (8.4/60) Hc Ho Int (Towards) Z ZN 32° 15.9’ - 7.4 32° 08.5’ 32° 28.7’ 20.2NM 143.3° 143.3° Index Correction Dip Sum Hs Ha Alt Add’l H.P. Ho + 2.1 - 6.7 - 4.6 32° 34.8’ 32° 30.2’ - 1.5 32° 28.7’ Date DR Lat DR λ OBS Time Watch Error Zone Time ZD GMT GMT Date 16 May 1995 39° 10’ N 157° 10’ W 2011 - 26 0 2011 - 26 + 10 0611 - 26 17 May 1995

  8. XI: Sight Reduction Plot of SPICA 158° W 157° W AP 39° N Sun LL0830 ZN = 143.3

  9. XI: Sight Reduction Reducing a Sun Sight Example: June 16, 1994 at 0515 – 23 ZT, in DR Position L 30° 10’ N λ 044° 35’ W. You Observe the Sun’s Upper Limb. Your Height of Eye Is 18 Feet, the Temp 88°F, and the Atmospheric Pressure Is 982mb. The Sextant Altitude Is 03° 20.2’. There Is No Index Error. SUN’S UL ☼ June 16, 1994 Hc Tab (+31.5 x 20.5/60) Hc Ho Intercept Z ZN 2° 28.8’ + 10.8’ 2° 39.6 2° 48.1’ 8.5 nm (towards) 064.7° 064.7° Index Correction Dip Sum Hs Ha Alt Add’l (T&B) H.P. Cor’n to Ha Ho 0 - 4.1’ - 4.1’ 3° 20.2’ 3° 16.1’ - 29.4’ + 1.4’ 0.0’ -28.0’ 2° 48.1’ Date DR Lat DRλ Zone Time ZD GMT Date GHA ☼ H M&S V GHA ☼ Assum. λ LHA ☼ Dec (d + 0.1) Dec Assum. Lat 16 June 1994 30° 10’ N 044° 35’ W 0515 – 23’ + 3’ June 16, 1994 299° 51.3’ 3° 50.8’ N.A. 303° 42.1 - 44° 42.1 (W) 259° N 23° 20.5 + 0.0 N 23° 20.5 N 30° (same)

  10. XI: Sight Reduction Plot The Sun 045° W 044° W C 120° 0515 DR. 064.7° ZN S 15kts AP 30° N Sun UL0515 ZN = 143.3

  11. Proceed in Same Manner As Sun Sight  XI: Sight Reduction Reducing a Moon Sight Example: At 1000 – 00 GMT, June 16, 1994 You Observe the Moon’s Upper Limb. Hs 26° 06.7’, Ht of Eye 18 Feet. No Index Error. Determine Ho, GHA and Declination of the Moon. Moon UL Index Correction Dip Sum Hs Ha Alt Add’l H.P. (58.4) Moon Upper Limits Cor’n to Ha Ho 0.0’ - 4.1 - 4.1 26° 06.7’ 26° 02.6 + 60.5’ 0.0 + 4.0’ - 30.0’ +34.5 26° 37.1’ GMT GHA M/S (v + 11.3) GHA Dec (d + 12.1) Dec 1000 - 00 245° 45.1 0° + 0.1 245° 45.2 S 00° 13.7’ + 0.1’ S 00° 13.8’

  12. Proceed in Same Manner As Sun Sight XI: Sight Reduction Reducing a Planet Sight Example: July 27, 1995, at 0945 – 20 GMT, You Observe Mars Hs 33° 20.5’, Ht of Eye 25 Feet. Index Correction Is + 0.2’. Determine Ho, GHA and Declination Mars Index Correction Dip Sum Hs Ha Alt Add’l H.P. Add’l Cor’n For Mars Cor’n to Ha Ho + 0.2’ - 4.9’ - 4.7’ 33° 20.5’ 33° 15.8’ - 1.5’ N.A. N.A. + 0.1’ - 1.4 33° 14.4’ GMT GHA♂ H M/S (v + 1.1) GHA♂ Dec (d + 0.6) Dec 0945 - 20 256° 10.6’ 11° 20.0’ + 0.8 267° 31.4’ S 01° 06.1’ + 0.5’ S 01° 06.6’

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