Astronomy 1 - September 16, 1998

Date: Wednesday - Sept 16, 1998
Topic: Horizon Coordinates and Time

NOTICES
	See the notice of the Halifax RASC meeting for Friday (previous lecture notes)
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HOMEWORK- Due next Wednesday (Sept 23)
	Chapter #1 Chaisson Problems # (see assignment on ACME)
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EQUIPMENT AND VISUAL AIDES
	Plastic Coordinate Sphere
          	overheads: 	Monthly movement
          			Star chart to show ecliptic and equator
          			Hour Angle and TIME overhead
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LECTURE 
	-- Star Charts and Constellations
			Outlines and labeling of stars
				Ancient Arabic etc names
				- Bayer letters (greek letters)
				- Numbering 
				- SAO numbers
				- HGSC numbers
				- HD numbers(Henry Draper Catalog)
			Scales of Atlases -
				limiting magnitude of stars plotted
				eg. Sky Atlas 2000.0 by Wil Tirion (43,000 stars to 8th mag)
				Nortons 2000.0 (8700 stars to 6.5 mag)
				ECU 1/4 million stars with SAO catalog to 9th mag
					16 million start with HGSC (CDROM) to 15th mag 
			example: (overheads of NGC7331 in Perseus)
				
	-- Horizon System (overhead transparencies)
          		Horizon related to Earth and Latitude,  Longitude
          		Altitude and Azimuth 
          			Examples: Show change in altitude and Azimuth on ECU
          		Calculation of Latitude from altitude of NCP
          		Terms: 	NCP, Celestial Meridian, Zenith, Zenith Distance
          		SCP, North Point, South Point, Celestial Equator

	-- Declination and Altitude of objects on the Local Meridian
		**Diagram to show how to calculate Altitude of Object on local meridian
          		Example - Trinidad and Shadow of vertical stick
          			(lat = 10 deg. May 30 solar dec = 21 deg)
          		Example: Altitude of Fomalhaut (dec = -30)
          			 Vancouver lat = 49 deg	  	

	-- Rotation of the Earth and Hour Angle
          	Longitude and Time of Rise
          	Star/sun motion
          	Hour angle (OVER HEAD on rotation)
          
          - Examples: Zenith Angle, Hour Angle etc of SUN 
          	Edmonton June 21, dec = 23, a = 53o, HA = 45o
          		(draw position - see notes)
          - RISE and SET
          	1- Moon Rise at latitude 45 deg example (notes)
          	2- Circumpolar stars and altitude versus latitude
          		Examples ( Victoria, Tucson, Wolfville)
          		Canopus visibility dec = -53 o
          		Southern Cross dec = - 63 o
          
          
          
          - TIME and HOUR ANGLE: Earth Rotation relative to the SUN 
          	HA = 0 to HA = 0 ----> 24 hours
          	60 minutes/hour  60 seconds/minute
			24 hour = 360 degrees
			 1 hour = 15 degrees of rotation
			 1 min time = 15/60 degrees = 1/4 degree
				OR 1 degree of Earth rotation = 4 minutes of time
					(this is useful to remember)
			 	also 1'arc of Earth rotation = 4 seconds of time
		
          Diagram of Time Zones and Hour Angles
          - TIME, TIMEZONES, and LONGITUDE
		1. 15 degree wide time zones 
		2. UT = Universal Time (Time at 0 degree Longitude)
		3. Offset of other timezones
			Atlantic Time (Longitude = 60W) 4 hours earlier
			Eastern Time (Longitude = 75W) 5 hours earlier
			etc
			(UT = AST + 4 hours)
			(AST = UT - 4 hours)
			(ADT = atlantic daylight time = AST + 1 hour)
		4. Offset of Local Mean Time

	- SIDERIAL DAY and SIDERIAL TIME
		Diagram of Siderial Rotation 
		Siderial Day = 4 minutes shorter than Solar Day
			360/36.986 x  86400 sec = 86164 sec
				shorter by 236 seconds (240 sec = 4 min)

	**Diagram of Siderial Time and Celestial Coordinate System  	
		ST = hour angle of Vernal Equinox
		RA = right ascension of celestial object
		HA = hour angle of Celestial object
		[ ST = HA + RA ] reduced to less than 24 hours

		If HA = 0 (object on the meridian)
		then ST = RA of celestial object on the local celestial meridian
			
		-Example:  What is the Siderial Time at the present time?
			We need HA and RA of some celestial object
			Use the Sun:  Time = 5 pm ADT (HA = 4 hours) explain!
				RA of the Sun = Sept 16 almost Autumnal Equinox
				On Sept 23 RA = 12 hr 
					1 day ~ 1 degree = 4 min time
					12 hr - (23 - 16)x 4 min = 12 hr - 28 min
					RA = 11-1/2 hr
			ST (now) = 4 + 11.5 = 15.5 hours
		- What is the HA of Jupiter (RA = 23.5 hrs)
			HA = ST - RA = 15.5 - 23.5 = - 8 hr
			8 hours before Jupiter gets on our local celestial meridian