Astronomy Facts

• 1 AU =
  
  150 million km (1.49 x 10⁸ km)
• Earth-Moon Distance = 384, 404 km
• c = 3 x 10⁸
• Stars travel from East to West
• Equatorial Coordinate System:
• Declination = height (NS) in degrees
• Right ascension = around (EW) in hours
• Planets go West-East
• Elongation: angular separation from Sun
• Ecliptic: apparent path of the Sun through the sky
• Eccentricity e = √(1-b²/a²)
• Major axis = 2a ; Minor axis = 2b
• Kepler's 1^st Law: Planets orbit the sun in elliptical orbits.
• Kepler's 2^nd law: The planets sweep out equal areas in the
  arc as they move around the Sun, and their speed changes accordingly.
• Kepler's 3^rd law: a³/P² = K, where K = 1 if a is in AU and P in years.
• Sidereal period: period of a celestial body relative to the stars
• Synodic period: period of a celestial body relative to a configuration with the Sun
• F = G (m₁m₂)/d²
• a³/P² = K(m₁ + m₂), K = 1/ m_Sun if a is in AU and P in years
• barycenter: center of mass of a binary system
• m_Earth/m_Moon ≈ 81
• T_F = 32 + 9/5 T_C
• T_C = 5/9 (T_F - 32)
  
• v = f x λ
• λ_UV = 400nm
• λ_IR = 700nm
• λ_max = 2,900,000/T
• F = σT⁴
• E = hf
• ∆λ/λ₀ = v/c
• Photon: least possible amount of electromagnetic energy in a given λ.
• Magnification = angular size through instrument / angular size
  through naked eye = Fl_obj/Fl_eye
• LGP Û area of objective or d_obj²
• Θ ≈ 2.5 x 10⁵ x λ/D (arcsecs and meters)
• Resolution Û d_obj
• f/number = aperture/focal length
• Small f/number Þ faster optics; good for observing the moon, planets and double stars (high power)
• Large f/number Þ slower optics; good for viewing deep-sky objects (low power)
• brightness Û (a/f)²
• Fl Û magnification
• Small angle formula: D ≈ A''/205,265 x d
• d_Earth = 12, 756km
• d_Moon = 3,476km
• Moon's sidereal period = 27.322 days
• Moon's synodic period = 29.531 days

Apogee's CCD University - How Telescopes Work