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Selection of stars lrg

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Selection of stars lrg

  1. 1. Grunt Productions 2007 Identification and Selection How to select and observe stars and planets. A brief by Lance Grindley
  2. 2. Grunt Productions 2007 Identification of Stars • Star or planet must be correctly identified so that the correct calculation can be made. • Stars can be recognised from well established patterns. Planets are usually brighter but reference may need to be made to NA. • Sights are usually taken at civil twilight when patterns are not so readily identified.
  3. 3. Grunt Productions 2007 Ursa Major or the Plough North Celestial Pole Polaris
  4. 4. Grunt Productions 2007 Ursa Major or the Plough North Celestial Pole Polaris
  5. 5. Grunt Productions 2007 Orion (Looking South) Sirius Rigel Aldebaran Betelgeuse Procyon Pollux Castor
  6. 6. Grunt Productions 2007 Pegasus and Cassiopeia Schedar Polaris Aloheratz Markab Marfak Hamal
  7. 7. Grunt Productions 2007 Predicted Alt and Az • Star identifier (NP 323) • Star Globe (may still be available) • Requirements: • LHA Aries for Star Identifier/Globe • Position (DR Latitude and longitude)
  8. 8. Grunt Productions 2007 Using the Star Identifier • Calculate the LHA Aries by working out the GHA Aries (listed hourly in NA), applying a correction for the number of minutes past the hour, and adding longitude east or subtracting longitude west. • Select the closest latitude overlay. • Lay the overlay on the star diagram, turning to align the arrow to the LHA Aries.
  9. 9. Grunt Productions 2007 Star Identifier (cont.) • Slide the overlay until the cross (indicating your zenith) lies on the correct latitude circle. • The overlay should be aligned so that the 180o line passes through the pole and the LHA shown on the outer circle. • The predicted bearing and altitude is read from the graticule printed on the overlay.
  10. 10. Grunt Productions 2007 Star Identification • Example • Date - 22 Jan 97 • DR- 42o 00’ N 051o 05’W • Time- 0715 (+3) • GHA Aries (1015Z) 275o 33.2’ • Long West 051o 05’ • LHA Aries 224o 28.2’
  11. 11. Grunt Productions 2007
  12. 12. Grunt Productions 2007 360 330 300 270 240 210 180 150 120 090 060 030 Latitude 40o
  13. 13. Grunt Productions 2007 360 330 300 270 240 210 180 150 120 090 060 030 Regulus Vega Align to LHA Aries Centre on Correct Lat Polaris
  14. 14. Grunt Productions 2007 Plotting Planets • Planets cannot be printed on the sheet because they move amongst the stars. • The Nautical Almanac lists the declination and sidereal hour angle (SHA) for the four navigational planets. • Planets can be plotted in pencil using this data. • Mars: Dec 1o North SHA 174o RA 186o
  15. 15. Grunt Productions 2007 Mars
  16. 16. Grunt Productions 2007 Selection of Stars/Planets • Easily seen (Brightest magnitudes, listed against stars/planets, are given the smallest number). • Altitude ideally between 20o and 60o. • Bearings (azimuth) either in reciprocal pairs or at least 30o apart.
  17. 17. Grunt Productions 2007 Bearings of Bodies Position Line Bearing of Star Position Line Bearing of Star Good Angle of Cut
  18. 18. Grunt Productions 2007 Reciprocal Bearings
  19. 19. Grunt Productions 2007 Star Selection (Example) • Magnitude Altitude Bearing Useable • 1.2 10° 25’ 035° Too Low • 3.2 42° 17’ 055° Too Faint • -0.2 35° 34’ 090° Good • 1.3 42° 22’ 105° Poor Cut • 0.3 82° 36’ 145° Too High • 1.5 45° 27’ 155° Good • 0.8 52° 12’ 225° Good
  20. 20. Grunt Productions 2007 Questions???

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