A. Celestial Sphere terminology:
- Celestial Terminology (Looking up from the surface of the Earth): Zenith, nadir, celestial poles, meridian, local meridian, celestial equator, & ecliptic
- Earth Terminology (Looking down upon a globe): Poles, equator, Latitude, & Longitude
- Both (Star and Earth) Terminology: Prime meridian, axis, horizon, Tropic of Cancer, & Tropic of Capricorn
B. The Problem of Longitude
- Why was it a problem?
- A reward was offered.
- Possible solutions
- The solution
C. Use telescopes
- Finding North
- Find and track the Moon, planets, stars, Sun, and other sky features
- Switching eyepieces
- Use Celestial Coordinate Systems
D. Celestial Coordinate systems
- Altitude and Azimuth – This is the coordinate system used by Alt-azimuth mounts. BOTH numbers change constantly. Both are measured in degrees - Altitude from 0 to 90 above the horizon, and Azimuth 360 around you (North is 0, and East is 90).
- Declination & Right Ascension - This is the coordinate system used on Equatorial mounts. They allow you to use any well-known star as a reference to find and track any object in the sky.
- Declination is absolute, and is exactly the same as Latitude, projected onto the sky. "Dec" is measured in degrees (Equator is 0 and the North Celestial Pole is 90North).
- Right Ascension is relative. Although the RA of a star will not change, the direction that your telescope is pointing IS changing constantly, so your reference for RA must be checked very often (every time you try to locate another object). "RA" is measured in hours, minutes, and seconds (0h 0m 0.0s through 23h 59m 59.9s), but should usually be rounded to hours and minutes depending upon the precision of the "setting circles" on the telescope.
- The Orion Nebula (M42)= Dec: -05deg 26' 58”. RA: 05h 35m 33.0s.
- Pleiades= Dec: 23 deg 47' 37”. RA: 03h 46m 16.1 s.
- You would probably round it to... Dec: 23.8 deg & RA: 3hr 46min
- SLR Camera
- CCD digital photography
- Hands-On Universe can manipulate FITS (.fts) files imaged by CCD's mounted to telescopes.