Table of Contents

Telescopes
Terminology
Purpose
Atmospheric Nomenclature
Questions

Intro to Astronomy
Misconceptions

Archaeoastronomy
Equitorial Coordinates
Understanding the Seasons

Atmospheric Nomeclature

1. Seeing: Steadiness of the atmosphere. Visually, good seeing is occurring when the stars do not twinkle (scintillate). Telescopically, images appear steady in good seeing. In conditions of bad seeing, stars scintillate vigorously. Lunar and planetary objects will appear to waver in a similar fashion as objects would appear if viewed down a long stretch of highway on a hot summer's day. Stagnant air, such as may be found on hot, humid summer nights often produces the best seeing conditions, even though few stars are visible. Seeing is usually worse in winter.
2. Transparency: Clarity of the earth's atmosphere. When the transparency is excellent, the night sky is black and "ablaze" with many faint stars. Stars of a faint magnitude are visible under good transparency conditions.
   1. Apparent magnitude: The measure of the amount of light (energy) received from a star or object at the earth's surface. It us usually referred to as just the magnitude of the object in conversation.
   2. The difference in intensity between two stars separated by one magnitude in brightness is equal to 2.51. A difference of five magnitudes is an intensity range of 100. 2.51 x 2.51 x 2.51 x 2.51 x 2.51 = 100.
   3. The more negative the magnitude, the brighter the object. A star of magnitude two is brighter than a star of magnitude three because two is a more negative number than three. Below are found the magnitudes of some common celestial objects.
      1. Sun:     - 26.7
      2. Moon:  - 12.7 (when full)
      3. Venus:  - 4.4 (at brightest)
      4. Sirius:   - 1.4 (brightest nighttime star in sky)
      5. Polaris: + 2.0 (North Star)
      6. + 6.0 (faintest star visible to average eye)