CELESTIAL NAVIGATION: HOW MUCH DO YOU ALREADY KNOW? PRESENTER: JEFF GOLDSTEIN, BBAA SECRETARY

HOW DO WE READ A SEXTANT?

CELESTIAL NAVIGATION TERMS -ALTITUDE (H S  H A  H O ) IC & DIP REFRACTION/PARALLAX -AZIMUTH (Z N ) -GREAT CIRCLES (MAKES CALCULATIONS EASY FOR LAN SHOOT) -LOCAL APPARENT NOON (LAN) -EQUATION OF TIME (ANALEMMA) (SLOW UNTIL APRIL 15, THEN FAST )  -MERIDIAN (WHEN THE SUN CROSSES OUR MERIDIAN, WHAT DIRECTION WILL WE BE LOOKING?) -INTERPOLATION (MATHEMATICAL CALCULATION TO APPROXIMATE PERCENTAGE BETWEEN TWO NUMBERS) -NAUTICAL AND AIR ALMANAC (ADVANTAGES?) -DECLINATION (OF A BODY) MEASURED FROM? -GREENWICH HOUR ANGLE (GHA MEASURED ONLY IN WHICH DIRECTION? ) -LOCAL HOUR ANGLE (LHA RELATES GREENWICH, YOU, AND THE OBSERVED BODY ) -SIDEREAL HOUR ANGLE ( SHA FOR STARS; RELATED TO RIGHT ASCENSION ) -RIGHT ASCENSION (NOT USED IN CELESTIAL NAVIGATION, BUT USED IN ASTRONOMY)  -ATMOSPHERIC REFRACTION OF ALL BODIES -PARALLAX (HP AND PA) OF THE SUN, MOON, OR MARS -SEMI-DIAMETER (SD) OF SUN AND MOON; WHY IS THIS IMPORTANT?

TONIGHT’S GOAL: LOCAL APPARENT NOON SIGHT DONE ON APRIL 3, 2016 (RELATIVELY) SIMPLE TO DETERMINE LAT. & LONG. FIX (Start the above video at 3:30 for his quick version of Local Apparent Noon Sight) Note also that he only uses his line of latitude. We will go further to refine our longitude, too. Here’s another YouTube on Celestial Lighthouses that is interesting and explains Celestial Navigation Terms

Today, what is the approximate declination of the sun? (think of the season and when summer begins) Don’t we need the exact declination for the sighting? We will interpolate exact declination between two from the table, later.

THE SUN’S GEOGRAPHIC POSITION : Sun’s Geographic Position & Zenith Distance = (90 – H o )* (where H o is the sun’s highest altitude found) But when will that be? We can predict it (Nautical Almanac)  add 4 minutes, since we’re at 76° W. Therefore, at approximately 17:07 UTC (12: hours Eastern Time Zone) ( or 13:07 EDT ) Also, what True Direction would we expect it? * Proof of (90 – H o ) on the next slide.

ARTIFICIAL HORIZON (ALWAYS GIVES 2X THE ACTUAL ALTITUDE)

Nautical Almanac

Air Almanac

FOR LATITUDE CALCULATIONS Latitude = (90 – H o ) ± Sun’s Declination N/S add for N, subtract for S Latitude = Sun’s Z.P. + Sun’s Declination N now above the equator

FOR LATITUDE CALCULATIONS Latitude = (90 – H o ) ± Sun’s Declination N/S add for N, subtract for S Latitude = Sun’s Z.P. + Sun’s Declination N now above the equator Latitude = (89° 60’ – H o ) + 5° 39.87’ Latitude = 31 ° 4.3’ + 5° 39.87’ Latitude = 36° 44.17’ Actual Lat: 36° ’ (error: miles)

FOR LONGITUDE CALCULATIONS We must have an accurate chronometer set to WWV, CHU Canada, or USNO (time hack). WWV on short wave radio frequencies: 5, 10, 15, 20, and 25 MHz. Recording: (i.d. at ) USNO online: or cell phone dial: (202) http://tycho.usno.navy.mil/simpletime.html CHU on short wave radio frequencies: 3.330, 7.835, MHz

LONGITUDE CALCULATIONS (CONT’D) Average the matching pairs of the same altitude (shot before and after LAN) 17 : 12 :: 05 = hours + 17 : 2 :: 25 = hours 34 : 14 :: 30 = hours ÷ 2 (for an average) 17 : 7 :: 15 = hours - 12 : 0 :: 00 5 : 7 :: 15 = the GHA - 3 :: 08 (from the Nautical Almanac) 5 : 4 :: 07 = the time corrected GHA 5(15) + 4(15/60) + 7(15/3600) = degrees =76° 1.75’ (error of nm)

RESOURCES “Davis Sextant User’s Guide: Mk 15 & Mk 25”, Hayward, CA. online Kreitlein, CDR Chris, USN Retired, “Simple Celestial: Navigation by the Heavens Made Easy”, 3 rd ed., Globus Horizon, Pensacola, Fla, “Nautical Almanac”, Commercial Edition, United Kingdom Hydrographic Office, “Nautical Almanac” 2016 Edition (online) Sailing Vessel Navigator, Chris “Going Further in Celestial Navigation: A Day with the Sun” “Sextant”, Wikipedia (online)

QUESTIONS ? & ANSWERS