1. Astronomy Basics Where is it? How to see it?
Angular positions in the sky
How far is it?
How to see it?
Telescopes

2. Positions on the Celestial Sphere
How to locate (and track) objects from a spinning, orbiting platform in space….

3. Positions on the Celestial Sphere The Altitude-Azimuth Coordinate System
Coordinate system based on observers local horizon
Zenith - point directly above the observer
North - direction to north celestial pole NCP projected onto the plane tangent to the earth at the observer’s location
h: altitude - angle measured from the horizon to the object along a great circle that passes the object and the zenith
z: zenith distance - is the angle measured from the zenith to the object z+h=90
A: azimuth - is the angle measured along the horizon eastward from north to the great circle used for the measure of the altitude

4. Changes in the Sky
Coordinates continuously changing in alt-az system for all celestial objects (except geo-stationary satellites)
Earth’s rotation
Earth’s orbit about Sun
Proper motion of objects
The moon
Planets
Asteroids
Comets
Satellites….
Milky Way From Frisco Peak. Paul Ricketts 

5. Motion of Stars about NCP

6. Earth’s Rotation
Earth’s rotation is responsible for the “rapid” motion of objects through the sky
Mud springs point 2 hour exposure of NCP. Paul Ricketts

7. Tilt of Earth’s Axis
Position of sun, moon and planets on celestial sphere significantly influenced by the tilt of Earth’s axis.
Stars far enough away that seasonal variation of position on celestial sphere not significantly influenced by the tilt of Earth’s axis…
On timescale of thousands of years, however, position of even stars move on celestial sphere due to precession!!!!

8. Earth’s Orbit about the Sun
Due to the Earth’s motion about the Sun :
Line of sight to the sun sweeps through the constellations. The sun apparently moves through the constellations of the zodiac along a path known as the Ecliptic
The constellations that are visible each night at the same time changes with the season
A given star will rise approximately 4 minutes earlier each day
The Ecliptic.The path of the sun through the year in equatorial coordinates.

9. Equatorial Coordinate System
Coordinate system that results in nearly constant values for the positions of distant celestial objects.
Based on latitude-longitude coordinate system for the Earth.
Declination - coordinate on celestial sphere analogous to latitude and is measured in degrees north or south of the celestial equator
Right Ascension - coordinate on celestial sphere analogous to longitude and is measured eastward along the celestial equator from the vernal equinox  to its intersection with the objects hour circle
Hour circle

10. Positions on the Celestial Sphere The Equatorial Coordinate System
Hour Angle - The angle between a celestial object’s hour circle and the observer’s meridian, measured in the direction of the object’s motion around the celestial sphere.
Local Sidereal Time(LST) - the amount of time that has elapsed since the vernal equinox has last traversed the meridian.
Right Ascension is typically measured in units of hours, minutes and seconds. 24 hours of RA would be equivalent to 360.
Can tell your LST by using the known RA of an object on observer’s meridian
Hour circle

11. What is a day? Solar day Sidereal day
The period (sidereal) of earth’s revolution about the sun is solar days. The earth moves about 1 around its orbit in 24 hours.
Solar day
Is defined as an average interval of 24 hours between meridian crossings of the Sun.
The earth actually rotates about its axis by nearly 361 in one solar day.
Sidereal day
Time between consecutive meridian crossings of a given star. The earth rotates exactly 360 w.r.t the background stars in one sidereal day = 23h 56m 4s

12. Annalemma Position of sun at “noon”
Mean (average) solar day is 24 hours
Equation of time
Position of sun at “noon”

13. Local Sidereal Time LST = 100.46 + 0.985647 * d + long + 15*UT
d is the days from J2000, including the fraction of
a day
UT is the universal time in decimal hours
long is your longitude in decimal degrees, East positive.
Add or subtract multiples of 360 to bring LST in range 0 to 360
degrees.

14. Precession of the Equinoxes
Precession is a slow wobble of the Earth’s rotation axis due to our planet’s nonspherical shape and its gravitational interaction with the Sun, Moon, etc…
Precession period is 25,770 years, currently NCP is within 1 of Polaris. In 13,000 years it will be about 47 away from Polaris near Vega!!!
A westward motion of the Vernal equinox of about 50” per year.

15. Celestial Coordinates Links…

16. Distance and Brightness
Stellar Parallax
The Magnitude Scale

17. Stellar Parallax
Trigonometric Parallax: Determine distance from “triangulation”
Parallax Angle: One-half the maximum angular displacement due to the motion of Earth about the Sun (excluding proper motion)
With p measured in radians

18. PARSEC/Light Year 1 radian = 57.2957795 = 206264.806”
Using p” in units of arcsec we have:
Astronomical Unit of distance:
PARSEC = Parallax Second = pc
1pc = x 105 AU
The distance to a star whose parallax angle p=1” is 1pc. 1pc is the distance at which 1 AU subtends an angle of 1”
Light year : 1 ly = x 1015 m
1 pc = ly
Nearest star proxima centauri has a parallax angle of 0.77”
Not measured until 1838 by Friedrich Wilhelm Bessel
Hipparcos satellite measurement accuracy approaches 0.001” for over 118,000 stars. This corresponds to a a distance of only 1000 pc (only 1/8 of way to center of our galaxy)
The planned Space Interferometry Mission will be able to determine parallax angles as small as 4 microarcsec = ”) leading to distance measurements of objects up to 250 kpc.

19. The Magnitude Scale
Apparent Magnitude: How bright an object appears. Hipparchus invented a scale to describe how bright a star appeared in the sky. He gave the dimmest stars a magnitude 6 and the brightest magnitude 1. Wonderful … smaller number means “bigger” brightness!!!
The human eye responds to brightness logarithmically. Turns out that a difference of 5 magnitudes on Hipparchus’ scale corresponds to a factor of 100 in brightness. Therefore a 1 magnitude difference corresponds to a brightness ratio of 1001/5=2.512.
Nowadays can measure apparent brightness to an accuracy of 0.01 magnitudes and differences to magnitudes
Hipparchus’ scale extended to m= for the Sun to approximately m=30 for the faintest object detectable

20. Flux, Luminosity and the Inverse Square Law
Radiant flux F is the total amount of light energy of all wavelengths that crosses a unit area oriented perpendicular to the direction of the light’s travel per unit time…Joules/s=Watt
Depends on the Intrinsic Luminosity (energy emitted per second) as well as the distance to the object
Inverse Square Law:

21. Absolute Magnitude and Distance Modulus
Absolute Magnitude, M: Defined to be the apparent magnitude a star would have if it were located at a distance of 10pc.
Ratio of fluxes for objects of apparent magnitudes m1 and m2 .
Taking logarithm of each side
Distance Modulus: The connection between a star’s apparent magnitude, m , and absolute magnitude, M, and its distance, d, may be found by using the inverse square law and the equation that relates two magnitudes.
Where F10 is the flux that would be received if the star were at a distance of 10 pc and d is the star’s distance measured in pc. Solving for d gives:
The quantity m-M is a measure of the distance to a star and is called the star’s distance modulus

22. A Brief talk about Telescopes
Types of Telescopes
Refractor
Reflector
Newtonian
Schmidt-Cassegrain ….
What Does a Telescope Do?
Light Collection
Image Formation
Pointing
Go-To Telescopes

23. Types
Refractor
Reflector
Catadioptric

24. Light Collection
The aperture of the optical instrument allows light coming from a source to be collected for image formation. The larger the aperture the more light is collected, therby allowing dimmer objects to be seen.
Meade LX200
14” diameter
Human Eye
1/4” diameter
99,314 mm^2
126 mm^2
Our 14” Meade has 788 times larger area than your eye

25. Light Collection Magnitude limit of 14” scope
Assume that the unaided eye can see down to 6th magnitude.
The amount of light collected increases with light collection area
14” scope hase 788 times the area of your eye
Magnitude Definition
Each 5 magnitudes  100 times the light
Each magnitude  =2.51 times the light
With 14” scope should be able to see down to magnitude 13.24

26. Image Formation
Lenses or Mirrors Focus light in such a way that the light rays emanating from one point on the object is focused to one point in the focal plane thereby forming an image of the object

27. Eyepieces and Magnification
Need eyepiece to examine image
Magnification =
Primary Focal Length
Eyepiece Focal Length

28. Resolution The ability to make out detail of an object
Separate binary stars
See features on extended objects
Diffraction limit
Maximum useful magnification

29. Focal Ratio Focal Length/Aperture “Speed/Brightness” of optics
f/8 requires 4x exposure time of f/4
Field of View
Smaller is faster and wider

30. Telescope Pointing Mount types Altitude-Azimuth Equatorial Fork
German Equatorial
Dobsonian

31. Altitude-Azimuth Mount

32. Equatorial Fork Mount

33. German Equatorial

34. Dobsonian Mount

35. Go-To Telescopes Alignment of Equatorial Mount Scopes Basic Setup
Computer
Location and Time
Use of Catalogs
Use of Coordintes
Telescope
Finderscope alignment
Basic Usage
Finding and Centering Objects
Focusing

36. Warnings !!!!! Know the basic operation before turning on scope
Be prepared to switch off/ stop scope from slewing
Watch cables…..