|Daily Motion||Long-term Motion|
|Sun||E to W in about 12 hours from sunrise to sunset. Length of day varies from season to season and with latitude.||W to E along the ecliptic 1 degree per day. The height of the sun in the sky at noon is at maximum in the summer, minimum in winter (excludes tropical regions). The sun returns to the same constellation in 1-year intervals.|
|Moon||E to W in about 12 hours, 25 minutes from moonrise to moonset. Moonrise is about 50 minutes later each day. Like the sun, this timing is modulated by the season and your latitude on Earth.||W to E within 5 degrees of the ecliptic. It takes 27.3 days to travel 360 degrees with respect to the stars, but phases repeat on a 29.5-day cycle.|
|Planets||E to W in about 12 from rising to setting (again modulated by season and latitude). Additional, very small variations are caused by the planets's own motions against the background stars.||W to E within 7 degrees of the ecliptic. The average speed varies according to planet. It is fastest for Mercury and slowest for Saturn (slower for Uranus, Neptune, Pluto but we can't see them with our eyes). All the planets have periods where they go retrograde (E to W) with timing different for each planet.|
|Stars||E to W in about 12 hours (modulated by season, by latitude, and by where the star is on the sky: circumpolar stars, for instance, do not rise and set, but they will travel in a circle around the pole, 180 degrees in 12 hours minus about 4 minutes.) Star rise is about 4 minutes (3m 56s) earlier each day.||The stars remain fixed on the celestial sphere with respect to themselves. The earth's pole describes a circular wobble of 23.5 degree amplitude centered on a point in the constellation of Draco every 26,000 years (often called "precession of the equinoxes").|
Long time exposures taken at night illustrate daily motion:
South Pole Star Trails 1 | South Pole Star Trails 2 | North Pole Star Trails
The red "Ecliptic" is the sun's path. The sun is at the vernal equinox around March 21 and travels eastward (increasing right ascension).
Just the celestial sphere plus the ecliptic, with solstices and equinoxes marked.
Drawn for northern latitudes, these are the paths the sun takes across the sky on the equinoxes and solstices. Can you see that the summer path is longer (and therefore that the summer sun stays in the sky longer)?
This figure illustrates that, depending on your latitude, some stars will be "circumpolar" and will never set. Remember: your latitude = the altitude of the north celestial pole.
|Observer's Latitude||Altitude of North Celestial Pole (Az.=0)||Altitude of South Celestial Pole (Az.=180)||Altitude of Celestial Equator (Az.= 0 or 180)||Declination of North horizon||Declination of South horizon||Declination of Zenith|
|30 (Caribbean)||30||-30||60 (Az. 180)||60 (i.e. 30 degrees beyond 90)||-60||30|
|60 (Canada)||60||-60||30 (Az. 180)||30||-30||60|
|90 (North Pole)||90||-90||0 (i.e. the horizon equals the celestial equator)||0||0||90|
This works south of the equator also, but you have to switch all of the "norths" with the "souths". The final point to make about this is that these latitude/declination/altitude correspondences are always true, but that longitude/right ascension correspondences depend on the hour of the day and also the season.
|Approx. Date||Label||Sun's Right Ascension||Sun's Declination|
|March 21||Vernal Equinox||0 hours||0 degrees|
|June 21||Summer Solstice||6 hours||+23.5 degrees|
|Sept 21||Fall Equinox||12 hours||0 degrees|
|Dec 21||Winter Solstice||18 hours||-23.5 degrees|
This is the standard everything-on-one-figure textbook diagram. It's a great summary figure after you have understood moon phases and timing. The view is from the north, looking down for the bottom half of the figure, but the view is from earth for the top row of moons. Diagram is not to scale.
|Phase||Sun-earth-moon angle (degrees)||Approx. time that moon crosses your meridian||Less 6 hr = rise time||Plus 6 hr = set time|
|New||0 or 360||noon||6 a.m.||6 p.m.|
|First Quarter||90||6 p.m.||noon||midnight|
|Full||180||midnight||6 p.m.||6 a.m.|
|Third Quarter||270||6 a.m.||midnight||noon|
Note that eclipses don't happen every month because the moon's orbit is tilted 5 degrees out of the earth-sun plane. So we really only get eclipse seasons twice a year (when the sun is on the "line of nodes" in the diagram below).
All 88 Constellation boundaries. | Constellation map, winter sky | Constellation map, summer sky | Constellation map, north polar region