Astronomy 305 Exam Topics

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Astronomy 305 Exam Topics

• Exam I Star Charts
• Exam II Coordinate Systems and Telescopes
• Exam III Planets, Comets and Asteroids
• Exam IV Stars and Deep Sky Objects

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Coordinate Systems

• 17 - Horizontal Coordinates
• 18 - Equatorial Coordinates
• 19 - Ecliptic Coordinates
• 20 - Galactic Coordinates
• 21 - Converting decimal degrees to , ,
• 22 - Converting Degrees to Hours
• 23 - Converting between Coordinate Systems
• 24 - Converting Right Ascension to Hour Angle
• 25 Equatorial to Horizontal Coordinate
  Conversation

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Celestial Coordinate Systems

• These are coordinate systems with two angular
  measurements
• Geographical
• Horizontal
• Equatorial
• Ecliptic
• Galactic

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Geographical System

• Latitude (f)
• the angle of a city above the equator
• Longitude (L)
• the angle around the equator from the Prime
  Meridian

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17 - Horizontal System

• Altitude (a)
• the angle of a star above the horizon
• Azimuth (A)
• the angle around the horizon from the north
  point measured eastward

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18 - Equatorial System

• Declination (d)
• Right Ascension (a)
• Hour Angle (H)
• the difference between the right ascension of
  your meridian and the right ascension an object

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24 Converting between a and H

• LST Local Sidereal Time
• LST is the same as the right ascension of the
  meridian on your star charts
• H LST a
• Examples
• What is the hour angle of Regulus at 1100 PM
  tonight?
• What is the hour angle of Sirius at 800PM
  tonight?

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Celestial Meridian
Hour Angle
d
H
Celestial Equator
90- f
S
H O R I Z O N
9
Celestial Meridian
d
Celestial Equator
a
?
90- f
S
H O R I Z O N
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19 - Ecliptic System

• Ecliptic Latitude (b)
• the angle of a star above the ecliptic
• Ecliptic Longitude (l)
• the angle around the ecliptic from the vernal
  equinox
• measured eastward
• labeled along the ecliptic on the star charts
• Obliquity (e)
• the angle between the ecliptic and the celestial
  equator and is approximately 23.5 degrees

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20 - Galactic System

• Galactic Latitude (b)
• the angle of a star above the galactic plane
• Galactic Longitude (l)
• the angle around the galactic plane
• measured eastward from the galactic center

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Examples Problem

• For all of the planets find
• their ecliptic longitudes
• the host constellation
• their equatorial coordinates
• Hint Use Appendix 11

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Planet Positions
Planet l a d Constellation
Mercury Venus Mars Jupiter Saturn Uranus
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Planet Positions
Planet l Visible? Rise Time Set Time
Mercury Venus Mars Jupiter Saturn Uranus
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Example Problems

• Calculate the altitude and azimuth of Capella for
  1100PM tonight.

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25 - Equatorial to Horizontal

• Step 1
• Find a, LST and H is decimal hours.
• Step 2
• Convert H to degrees.
• Step 3
• Convert d to decimal degrees.

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• Step 4
• Find sin a sin d sin f cos d cos f cos H
• Step 5
• Find a
• Step 6
• Find

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• Step 7
• Find A
• Step 8
• If sin H is negative, A A
• If sin H is positive, A 360 A
• Step 9
• Find a and A in degrees, minutes and seconds.

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More Examples

• What are the coordinates of Jupiter on May 5,
  2005 at 800PM?
• b
• l
• a
• d
• LST
• H
• a
• A

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Reading Assignment

• Chapter 2
• A Tour of the Sky
• Chapter 3
• The Monthly Sky Maps
• Chapter 16
• Telescopes and Binoculars

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More Examples

• What are the coordinates of Venus tonight at
  700pm?
• b
• l
• a
• d
• LST
• H
• a
• A

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25 - Equatorial to Horizontal

• Step 1
• Find a, LST and H is decimal hours.
• Step 2
• Convert H to degrees.
• Step 3
• Convert d to decimal degrees.

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• Step 4
• Find sin a sin d sin f cos d cos f cos H
• Step 5
• Find a
• Step 6
• Find

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• Step 7
• Find A
• Step 8
• If sin H is negative, A A
• If sin H is positive, A 360 A
• Step 9
• Find a and A in degrees, minutes and seconds.

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More Examples

• Suppose that the Moon occults the star Antares
  on Feb 6th. Find the following for the Moon
• a
• d
• b
• l

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Ecliptic Coordinates

• Step 1
• Find a and d.
• Step 2
• Find a and d in decimal degrees.
• Step 3
• Find sinb sind cose cosd sine sina

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• Step 4
• Find b.
• Step 5
• Find y sina cose tand sine
• Step 6
• Find x cosa

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• Step 7
• Find l.

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More Examples

• On what day does Vega cross the meridian at 800
  PM?
• What is the maximum altitude of the Sun for today
  in Nacogdoches?
• At approximately what time does the Sun cross the
  meridian today?
• What is the maximum altitude of the Sun over one
  year?