Lab 6- Celestial Navigation: Star Charts

1. Tyler Junior College Physics & Astronomy Presents- Lab 6- Celestial Navigation:Star Charts

2. Celestial Coordinates • When we look up at the sky, there are also space & time references. • Earth Celestial • Latitude Declination (dec.) • Equator Celestial Equator • North Pole Celestial North Pole • Longitude Right Ascension (R.A.)

3. Celestial Sphere

4. Celestial Latitude-Declination Stars above the Celestial Equator Have a Positive Declination. (dec. = +XX°) Stars below the Celestial Equator have a Negative Declination. (dec. = -XX°)

5. Other Celestial Terms • Ecliptic-The path the Sun takes as it travels across the sky. • Zenith-Point directly overhead. • Horizon-points where the sky meet the Earth. • Azimuth (Bearing)-measure of the points on the horizon measured from Celestial North in degrees.

6. Celestial Longitude-Right ascension (R.A.) • Right Ascension is the East-West coordinate systems for the celestial sphere. The Celestial Prime Meridian. • I t is measured in a system similar to UT, i.e. Hrs, Min, and sec. (00h 00m 00s). • The point of 00h 00m 00s is the point on the Sun’s northward path (Ecliptic) as it crosses the celestial equator (0° dec.) on about March 21th of each year known as the Vernal Equinox. • The star ω Pisces lines on this line (up/down). • R.A. run Eastward around the celestial sphere.

7. Dates Each mark is 5m. NCP Right Ascension 10° 1h Each mark is 1°. Apparent Magnitude Symbols Declination (° )

8. Dates of the Year (Mar. 21 to May 22) Decl inaton 0h Right Ascension Ecliptic Celestial Equator Each mark is 1° Right Ascension Each mark is 5m.

9. Finding dec. and R.A. of a star • Dec.-Declination is vertical. Find the star and draw a line to the left or right side of the chart with is closer. Find the dec. to the nearest 1°. • NOTE: ON SC-1, DRAW R.A. LINE TO THE EDGE AND COPY ALONG COORDINANCE. MEASURE ON COORDINANCE BY COUNTING MARKS. • R.A. Is horizontal. Find the star and draw a line to the bottom (only) . Find the R.A. to nearest 5m. • NOTE: ON SC-1, DRAW LINE RADIALLY TO EDGE. FIND MARK BETWEEN Xh (hour values) AND COUNT MARKS BETWEEN EACH 10° VALUES.

10. 3h Algol (β PERSEUS) 2nd Mark dec. 4h dec.: +41° R.A. R.A.: 3h 10m 1st mark Above +40°

11. MARKAB-(α PEGASUS) Dates of the Year (Mar. 21 to May 22) dec.: +15° R.A.: 23h5m Decl inaton 0h Right Ascension Ecliptic +20° 5th Mark +10° Celestial Equator 24h 23h Each mark is 1° Right Ascension Each mark is 5m. 1st Mark

12. Naming Stars • There are several different methods of naming stars in constellations. The ancients gave the brightest 275 stars personal name, about 50 of which are still called by their personal names today. Arcturus , the brightest star in Boötes, is an example. • Other methods, which are ore useful to the astronomer, are those in which the stars are designated by some systematically ordered manner.

13. Naming Stars • German astronomer Johann Bayer in 1603, assigned a lower-case Greek letter to each star followed by the Latin name of the star’s parent constellation in genitive (possessive) form. Vega is α (alpha) in the constellation LYRA (See below). The genitive form is Lyri, so Vega is α LYRI. For this class we use the name of the constellation, so Vega is α LYRA. • NOTE: Constellations are spelled in all caps. • Stars in each constellation were given Greek letter ( in order) from the brightest to the dimmest. The brightest star in each constellation was label alpha (α). The next brightest, beta (β), then gamma (γ),…eventually to the dimmest , omega (ω).

14. Naming Stars • There are only 24-25 Greek letters. For constellations with more that 25 stars, he added lower case Latin letters, and then upper case Latin letter ending in Q. (We won’t need these and only about 10-12 Greek letters. BE ABLE TO PRONOUCN AND WRITE THE LOWER CASE GREEK LETTERS!!!!!!!!!!!!!

15. Apparent Magnitude • Apparent Magnitude-is the measure of the brightness of a celestial luminous body as seen by an observer on Earth, normalized to the value it would have in the absence of our atmosphere. The larger the apparent magnitude the fainter the body is. • The symbols for apparent magnitude run from -2 upward, with -2 stars represented by larger dots.

16. Star Apparent Magnitude • To find (estimate) the apparent magnitude of a star on a star chart, you can do it two ways: • Measure the diameter of the magnitude scale symbols and then measure the diameter of the star of interest. • On the edge a piece of paper, draw the diameter of the magnitude scale symbols on the paper from left to right in descending order of the magnitudes.

17. The EcLiptic-Earth/Sun Plain ECLIPTIC-Path of Sun, Planets, some stars, some constellations and sometimes-the Moon. CE

18. Signs of the Astronomical Zodiac Constellations along the Ecliptic

19. Zodiac-12 Constellations CE

20. The Sun in the Ecliptic Effects on Earth. • The farthest North that the Sun is at Zenith is the Tropic of Cancer. This occurs on June 22 and begins Summer (Northern Hemisphere [NH]) {Winter –Southern Hemisphere [SH]}. It is termed the Summer or Northern Solstice (NH) [opposite for SH] • The farthest South that the Sun is at Zenith is The Tropic of Capricorn. This occurs on December 22 and begins Winter (NH). It is termed the Winter or Southern Solstice (NH).

21. The Sun in the Ecliptic Effects on Earth. • The Sun crosses the Equator going North on March 21. This begins Spring (NH) and is termed the Vernal or Spring Equinox . • The Sun crosses the Equator going South on September 23. This begins Fall or Autumn (NH) and is termed the Autumnal or Fall Equinox.

22. TROPIC OF CANCER EQUATOR TROPIC OF CAPRICORN

23. Why?

24. Why? Summer Solstice

25. Why? Winter Solstice

26. Lab 6 Celestial Navigation- Star Charts The End