Astronomy and Observation

Observing the Universe

Astronomy

• The Night Sky: The Celestial Show for the Current Month
• Star Sizes: How the Michelson and Brown-Twiss stellar interferometers work
• Mars: A celebration of the favorable opposition of 2003.
• Stellar Magnitudes: an explanation of this logarithmic scale and the effects of the energy spectrum.
• Longitude: Time and position at sea
• Calendars: What they mean, and how they are devised
• The Lunar Mansions: Motions of the Moon, and Astrology
• Magnetic Storms: solar activity has effects on communications, power and pipelines.
• Shadows and Eclipses: shadow lore.
• Celestial Mechanics: calculating the positions of planets, comets and earth satellites.
• Internet Links: in astronomy, weather and related fields.

Meteorological Optics

• The Rainbow: how Descartes and Airy explained it.
• The Glory: the theory of this impressive sight was long in doubt.
• The Halo: scattering from ice crystals.
• The Corona: diffraction by water and ice.
• The Mirage: an explanation of the five principal mirage phenomena.
• The Heiligenschein: geometrical optics of the sphere.
• Visibility: scattering in the atmosphere; blue skies and red sunsets.
• The Green Flash: a link to an excellent website.

Observation

• Sky Observations by Day: Contrail Shadows, Billow Clouds, Sun Dogs, Halos, Venus
• Dawn: 18 June begins in Denver.
• The Gnomon: Making and using the oldest astronomical instrument
• The Lensatic Compass: what it is and how to use it.
• The Mirror (Brunton) Compass: what it is and how to use it.
• The Abney Clinometer: what it is and how to use it.
• The Stadia: rapidly measuring distances by angular subtense.

The graphic shows the planet Uranus, with satellites Ariel and Miranda, and a dust ring, in a false-color infrared composite image. The blue is methane. (Subaru/Hawaii)