Selection of stars lrg

Grunt Productions 2007

Identification and Identification and SelectionSelection

How to select and observe How to select and observe stars and planets.stars and planets.

A brief by Lance GrindleyA brief by Lance Grindley


Identification of StarsIdentification of Stars• Star or planet must be correctly identified Star or planet must be correctly identified

so that the correct calculation can be made.so that the correct calculation can be made.

• Stars can be recognised from well Stars can be recognised from well established patterns. Planets are usually established patterns. Planets are usually brighter but reference may need to be brighter but reference may need to be made to NA.made to NA.

• Sights are usually taken at civil twilight Sights are usually taken at civil twilight when patterns are not so readily identified.when patterns are not so readily identified.


Ursa Major or the Ursa Major or the PloughPlough

North Celestial Pole

Polaris


Orion (Looking South)Orion (Looking South)

Sirius

Rigel

Aldebaran

Betelgeuse

Procyon

Pollux

Castor


Pegasus and CassiopeiaPegasus and Cassiopeia

Schedar

Polaris

Aloheratz

Markab

Marfak

Hamal


Predicted Alt and AzPredicted Alt and Az

• Star identifier (NP 323) Star identifier (NP 323)

• Star Globe (may still be available)Star Globe (may still be available)

• Requirements:Requirements:

• LHA Aries for Star Identifier/GlobeLHA Aries for Star Identifier/Globe

• Position (DR Latitude and longitude)Position (DR Latitude and longitude)


Using the Star IdentifierUsing the Star Identifier

• Calculate the LHA Aries by working out the Calculate the LHA Aries by working out the GHA Aries (listed hourly in NA), applying a GHA Aries (listed hourly in NA), applying a correction for the number of minutes past correction for the number of minutes past the hour, and adding longitude east or the hour, and adding longitude east or subtracting longitude west.subtracting longitude west.

• Select the closest latitude overlay.Select the closest latitude overlay.

• Lay the overlay on the star diagram, turning Lay the overlay on the star diagram, turning to align the arrow to the LHA Aries.to align the arrow to the LHA Aries.


Star Identifier (cont.)Star Identifier (cont.)

• Slide the overlay until the cross Slide the overlay until the cross (indicating your zenith) lies on the correct (indicating your zenith) lies on the correct latitude circle.latitude circle.

• The overlay should be aligned so that the The overlay should be aligned so that the 180180oo line passes through the pole and the line passes through the pole and the LHA shown on the outer circle.LHA shown on the outer circle.

• The predicted bearing and altitude is The predicted bearing and altitude is read from the graticule printed on the read from the graticule printed on the overlay. overlay.


Star IdentificationStar Identification

• Example Example

• Date - 22 Jan 97Date - 22 Jan 97

• DR- 42DR- 42oo 00’ N 051 00’ N 051oo 05’W 05’W

• Time- 0715 (+3)Time- 0715 (+3)

• GHA Aries (1015Z) GHA Aries (1015Z) 275275oo 33.2’ 33.2’

• Long WestLong West 051051oo 05’ 05’

• LHA AriesLHA Aries 224224oo 28.2’ 28.2’


360330

300

270

240

210

180

150

120

090

060

030

Latitude 40o


360330

300

270

240

210

180

150

120

090

060

030

360

330

300

270

240

210

180

150

120

090060

030

360

330

300

270

240

210

180

150

120

090060

030

Regulus

Vega

Align to LHA Aries

Centre on Correct Lat

Polaris


Plotting PlanetsPlotting Planets

• Planets cannot be printed on the sheet Planets cannot be printed on the sheet because they move amongst the stars.because they move amongst the stars.

• The Nautical Almanac lists the The Nautical Almanac lists the declinationdeclination and and sidereal hour angle sidereal hour angle (SHA)(SHA) for the four navigational planets. for the four navigational planets.

• Planets can be plotted in pencil using Planets can be plotted in pencil using this data.this data.

• Mars: Mars: Dec 1Dec 1oo North SHA 174 North SHA 174o o RA RA 186186oo


Mars

360

330

300

270

240

210

180

150

120

090060

030


Selection of Selection of Stars/PlanetsStars/Planets

• Easily seen (Brightest magnitudes, Easily seen (Brightest magnitudes, listed against stars/planets, are listed against stars/planets, are given the smallest number).given the smallest number).

• Altitude ideally between 20Altitude ideally between 20oo and and 6060o.o.

• Bearings (azimuth) either in Bearings (azimuth) either in reciprocal pairs or at least 30reciprocal pairs or at least 30oo apart.apart.


Bearings of BodiesBearings of Bodies

Position Line

Bearing of Star

Position Line

Bearing of Star

Good Angle of Cut


Reciprocal BearingsReciprocal Bearings


Star Selection Star Selection (Example)(Example)

• MagnitudeMagnitude AltitudeAltitude BearingBearing UseableUseable

• 1.21.2 10° 25’10° 25’ 035°035° Too LowToo Low

• 3.23.2 42° 17’42° 17’ 055°055° Too FaintToo Faint

• -0.2-0.2 35° 34’35° 34’ 090°090° GoodGood

• 1.31.3 42° 22’42° 22’ 105°105° Poor CutPoor Cut

• 0.30.3 82° 36’82° 36’ 145°145° Too HighToo High

• 1.51.5 45° 27’45° 27’ 155°155° GoodGood

• 0.80.8 52° 12’52° 12’ 225°225° GoodGood


Questions???Questions???

Selection of stars lrg

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