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Light List for the Sky

Celestial Coordinates. Junior Navigation Chapter 5. Light List for the Sky. Junior Navigation Chapter 6. Selecting DIP Correction. HE 14.1ft corr -3.6’ HE 14.4 ft corr -3.7’ HE 14.9ft corr -3.7’. 14 . 4.

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Light List for the Sky

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  1. Celestial Coordinates Junior Navigation Chapter 5 Light List for the Sky Junior Navigation Chapter 6

  2. Selecting DIP Correction HE 14.1ft corr -3.6’ HE 14.4 ft corr -3.7’ HE 14.9ft corr -3.7’ 14.4 If an entry falls on an exact number in these tables, use the upper correction (“upper” means the correction that is physically higher on the page). 2

  3. Learning Objectives Define declination, hour circle, GHA, and LHA Understand how the GP of a body is located by celestial coordinates, and relationships among hour angles Obtain GHA and declination of the sun from the Nautical Almanac Calculate LHA and declination from Nautical Almanacdata 3

  4. Defining Positions To obtain a celestial LOP you need: Ho, altitude of celestial body you observed Hc, altitude you calculated from your DR To calculate Hc, you need to know LHA & Dec 4

  5. Terrestrial Positions Latitude – measured from equator along a meridian of longitude, N or S, to maximum of 90º Longitude– measured from prime meridian along a parallel of latitude, E or W, to a maximum of 180º Coordinates? GP 5

  6. Celestial Positions Coordinates Starting Points Great Circles GHA Dec LHA Celestial Equator Greenwich Celestial Meridian Hour Circle Parallel of Declination Greenwich Hour Angle Declination Local Hour Angle GP (longitude) measured along the celestial equator West to maximum of 360º (latitude) measured along hour circle from equator, N or S, to maximum of 90º 6

  7. Computing LHA LHA - need to compute local hour angle of body Relationship between LHA and GHA is defined as: (cos LHA x cos Lat x cos Dec) + (sin Lat x sin Dec) = sin Hc LHA = GHA – West Longitude or LHA = GHA + East Longitude 7

  8. LHA = GHA – West Longitude M Lo W GHA LHA LHA GHA Lo W m 15º 30º G 45º 45º 120º 60º 75º LHA = GHA 120º – Lo 45º W LHA = 75º g 8

  9. LHA = GHA + East Longitude M Lo E LHA GHA Lo E m 15º 30º G 45º 45º 315º 60º 300º 75º 285º LHA = GHA 270º + Lo 45º E LHA = 315º 270º 90º 255º 105º LHA 240º 120º GHA 225º 135º 270º 150º 210º g 165º 195º 180º 9

  10. LHA = GHA – West Longitude M LHA = GHA 90º – Lo 150º W LHA = 300º + 360º GHA 450º– Lo 150º W m g Lo W 150º GHA 90º LHA ? G 10

  11. Meridian Transit When sun directly over Observer’s Meridian: Details in Chapter 9 Sun reaches its maximum altitude Body is due North or South Lo = GHA LHA = 000º Lo W GHA M g G 11 m

  12. Sun Overhead An observer sees the sun directly overhead, Ho 90º00.0’ Nautical Almanac lists Sun GHA as 298° and Sun’s Dec is 20° N What is your latitude and longitude? Since Dec = 20°N, then Lat = 20°N GHA of the sun > 180°, so GP of sun is East Lo GHA of the sun 360° – 298° = 62° E 12

  13. Published annually by the Nautical Almanac Office of the U.S. Naval Observatory. The Almanac 2013 2013 NAUTICAL ALMANAC COMMERCIAL EDITION NAUTICAL ALMANAC 2013 COMMERCIAL EDITION JAN 1 2013 THROUGH JAN 1 2014 13

  14. 2013 JANUARY 10, 11, 12 (THU., FRI., SAT.) THURSDAY THURSDAY LEFT PAGE GHA for Aries, and the GHA & Dec plus Magnitude, SHA, & Mer. Pass. for the four Navigational Planets, and the SHA & Dec for the 57 Navigational Stars FRIDAY FRIDAY Sun or moon symbols: continuous above horizon continuous below horizon twilight lasts all night SATURDAY SATURDAY The Daily Pages 2013 JANUARY 10, 11, 12 (THU., FRI., SAT.) RIGHT PAGE GHA & Dec for Sun and Moon plus times for nautical and civil twilight, sunrise, moonrise, sunset, moonset, and time of meridian passage for sun and moon. 14

  15. Increments and Corrections Two minutes per page • Used to interpolate between whole-hour values of GHA & Dec • Tables for each minute of the hour • ‘v’ (variable motion) & ‘d’ (declination) corrections • ‘v’ correction for sun included in hourly values of GHA; other ‘v’ corrections in Navigation • ‘d’ correction needed for sun 15

  16. Other Almanac Pages Calendars – Public holidays by country; religious holidays for United States; moon phase calendar, Julian calendar Eclipses Standard times through-out the world Star charts Polaris tables Sight reduction procedures Sight reduction tables (NASR method) Conversions of arc to time Altitude correction tables for the moon 16

  17. Sight Reduction Form IGNORE IGNORE IGNORE 17

  18. Find UT and LHA and Dec On 10 May you make an observation of the sun from St. Paul, at 17 – 34 – 37 WT and your WE is 8 sec slow 10 May 2012 17 – 34 – 37 00 – 08 + 17 – 34 – 45 5 + 22 – 34 – 45 10 May 2012 18

  19. Find UT and LHA and Dec IGNORE m 34 SUN PLANETS ARIES MOON 22 8 41.9 8 40.5 8 16.8 41 8 40.3 8 41.7 8 16.5 8 17.0 8 40.8 8 42.3 34 45 42 8 41.0 8 42.4 8 17.3 43 44 8 41.3 8 42.7 8 17.5 8 17.7 8 41.5 8 42.9 45 92 14 5 8 18.0 8 41.8 8 43.2 46 8 42.0 8 18.2 8 43.4 47 8 43.7 8 42.3 8 18.5 48 49 UT is 22 – 34 – 45 and longitude is 92º 14.5’ W CALCULATE SECOND PAGE FIRST PAGE 1 150 55 0 4 8 41 3 IGNORE 2 22 17 49 8 IGNORE 3 ? 159 36 3 ? 0 6 + 5 ? – 0 3 + ? 67 21 8 ? 17 50 1 19

  20. Find UT and LHA and Dec M LHA67.3º Lo W 92.2º GHA 159.5º ZT 1735 UT 2235 m g G 20 zm

  21. Extract LHA & Dec Data IGNORE • Your DR Lo is 34°33.3´W when you take a sight on the sun at UT 10–38–12 on 19 March. ? 10 328 03 0 ? 9 33 0 38 12 IGNORE ? 10 0 26 0 IGNORE ? ? ? 337 36 0 1 0 – ? ? 34 33 3 – 0 6 – ? ? 303 02 7 0 25 4 21

  22. Extract LHA & Dec Data IGNORE • Your DR Lo is 34°33.3´W when you take a sight on the sun at UT 12–38–10 on 20 March. ? 12 358 07 8 ? 9 32 5 38 10 IGNORE ? 12 0 00 3 IGNORE ? ? ? 367 40 3 1 0 – ? ? 34 33 3 – 0 6 – ? ? 333 07 0 0 00 3 22

  23. LHA, Dec & Ho On 17 August, from the point at Bayport Marina, you observe the LL of the sun at WT 08-57-12 DST; WE is 1min 08sec slow; recording a sextant height of 27°35.2’; IE reading is 53.4’ off the arc; HE is 22.0ft and distance to far shore is 0.5nm GPS reads N45°00.170' W092°46.534' Complete the upper part of the SR96 (USPS Sight Reduction Form), calculating LHA, Dec, Ho, and draw time diagram. 20 18 16 14 12 10 8 6 4 2 READY FOR YOUR ANSWERS? 23

  24. USPS SR96 1 17 August 22 0 Sun LL 08-57-12 27 35 2 45 00 2 1-08 + 92 46 5 6 6 08-58-20 25 1 5 + 6 6 25 1 13-58-20 18 5 - 17 August 27 16 7 g G 14 2 14 00 5 13 20 14 35 0 58 zm 13 13 17 4 14 2 0 0 28 35 5 14 2 0 8 + - 92 46 5 0 8 - - 27 30 9 295 49 0 13 16 6 NEXT WEEK bring calculator Ds = (0.4156 x d) + [0.5658 x (h/d)] Ds = (0.4156 x 0.5) + [0.5658 x (22/0.5)] Ds = 0.2078 + (0.5658 x 44) Ds = 0.2078 + 24.8952 Ds = 25.103 Hc 27 31.3’ Ho 27 30.9’ 24

  25. Quiz 1. The coordinates of the GP of the sun are: Lat 7° 09.5' S, Lo 150° 04.2' E. a. What are the GHA and declination of the sun at this time? GHA = 209° 55.8' [GHA = 360° - Lo E] Dec = 7° 09.5'S b. If the LHA of the sun at the same time is 48°32.1' what is the observer's Lo? Lo = 161°23.7' W [Lo W = GHA - LHA] 25

  26. Quiz 2. You have determined your position by GPS to be Lat 23° 01.8' N, Lo 76° 56.3'. You look up and see the sun directly overhead. What are the Declination, GHA, and LHA of the sun at this time? Declination of the sun: 23° 01.8'N GHA of the sun: 76°56.3' LHA of the sun: 000° 26

  27. Quiz • 3. All meridians of longitude and parallels of latitude are great circles. • True • b. False 27

  28. Quiz 4. Fill in the blanks in the following statements about celestial coordinates: a. __________is the angular distance of the GP of a body north or south of the equator. b. ___________________is the angular distance from the Greenwich meridian westward to the hour circle of a body. c. ______________ is the angular distance from an observer's local meridian westward to the hour circle of a body. Declination Greenwich Hour Angle Local Hour Angle 28

  29. Quiz 5. When finding declination of the sun from the Nautical Almanac, a d correction must be determined. a. Trueb. False. 29

  30. Quiz 6. Using the Excerpts from the Nautical Almanac for August 24, will the d value be entered on the Sight Reduction form as positive or negative? a. positiveb. negative 30

  31. Quiz 7. Using the Excerpts from the Nautical Almanac, what is the declination of the sun for 1400 UT on March 30? Declination of the sun = _________ 3° 57.0' N 31

  32. Quiz 8. Declination of the Sun is equal to the Hour Declination _____________ the d correction. a. plusb. minusc. plus or minus plus or minus 32

  33. Quiz 9. The local hour angle (LHA) is found by __________ DR Lo(W) from the GHA of the Sun. a. addingb. subtracting subtracting 33

  34. Celestial Coordinates End of Junior Navigation Chapters 5 & 6 34

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