# Astronomy 305 Exam Topics Exam I – Star Charts

## Presentation on theme: "Astronomy 305 Exam Topics Exam I – Star Charts"— Presentation transcript:

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

17 - Horizontal System Altitude (a) Azimuth (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 8:00PM tonight?

Hour Angle S H O R I Z O N Celestial Meridian d H Celestial Equator
90°- f S H O R I Z O N

Celestial Meridian d Celestial Equator a 90°- f S H O R I Z O N

19 - Ecliptic System Ecliptic Latitude (b) Ecliptic Longitude (l)
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) Galactic Longitude (l)
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… Hint: Use Appendix 11
their ecliptic longitudes the host constellation their equatorial coordinates Hint: Use Appendix 11

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

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

Example Problems Calculate the altitude and azimuth of Capella for 11:00PM 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 Step 5 Step 6 Find sin a = sin d sin f + cos d cos f cos H
Find a Step 6 Find

Step 7 Step 8 Step 9 Find A’ 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 8:00PM? b l a d LST H A

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

More Examples What are the coordinates of Venus tonight at 7:00pm? b l
LST H 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 Step 5 Step 6 Find sin a = sin d sin f + cos d cos f cos H
Find a Step 6 Find

Step 7 Step 8 Step 9 Find A’ 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 6th. Find the following for the Moon: a d b l

Ecliptic Coordinates Step 1 Step 2 Step 3 Find a and d.
Find a and d in decimal degrees. Step 3 Find sinb = sind cose – cosd sine sina

Step 4 Step 5 Step 6 Find b. Find y = sina cose + tand sine
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?