Astronomy 305 Exam Topics Exam I Star Charts

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

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

Celestial Coordinate Systems ¬These are coordinate systems with two angular measurements: • Geographical • Horizontal • Equatorial • Ecliptic • Galactic

Geographical System ¬Latitude (f) – the angle of a city above the equator ¬Longitude (L) – the angle around the equator from the Prime Meridian

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

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

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 11: 00 PM tonight? – What is the hour angle of Sirius at 8: 00 PM tonight?

Celestial Meridian d H Celestial Equator 90°- f S HORIZON

Celestial Meridian d Celestial Equator a 90°- f S HORIZON

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

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

Examples Problem ¬For all of the planets find… – their ecliptic longitudes – the host constellation – their equatorial coordinates ¬Hint: Use Appendix 11

Planet Positions Planet Mercury Venus Mars Jupiter Saturn Uranus l a d Constellation

Planet Positions Planet Mercury Venus Mars Jupiter Saturn Uranus l Visible? Rise Time Set Time

Example Problems ¬Calculate the altitude and azimuth of Capella for 11: 00 PM tonight.

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.

¬Step 4 Find sin a = sin d sin f + cos d cos f cos H ¬Step 5 Find a ¬Step 6 Find

¬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.

More Examples ¬ What are the coordinates of Jupiter on May 5, 2005 at 8: 00 PM? ¬b ¬l ¬a ¬d ¬ LST ¬H ¬a ¬A

Reading Assignment ¬Chapter 2 – A Tour of the Sky ¬Chapter 3 – The Monthly Sky Maps ¬Chapter 16 – Telescopes and Binoculars

More Examples ¬ What are the coordinates of Venus tonight at 7: 00 pm? ¬b ¬l ¬a ¬d ¬ LST ¬H ¬a ¬A

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.

¬Step 4 Find sin a = sin d sin f + cos d cos f cos H ¬Step 5 Find a ¬Step 6 Find

¬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.

More Examples ¬Suppose that the Moon occults the star Antares on Feb 6 th. Find the following for the Moon: ¬a ¬d ¬b ¬l

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

¬Step 4 Find b. ¬Step 5 Find y = sina cose + tand sine ¬Step 6 Find x = cosa

¬Step 7 Find l.

More Examples ¬On what day does Vega cross the meridian at 8: 00 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?