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Definition
| The imaginary sphere that surrounds the Earth |
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| North and South Celestial Poles |
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| The points in the sky directly above the North and South poles |
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| An imaginary circle around the sky directly above the Earth's equator |
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| The point straight overhead on the celestial sphere for any observer |
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| The arc that goes through the north point on the horizon, zenith, and south point on the horizon |
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| The number of degrees north or south of the Earth's equator |
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| The number of degrees east or west of the Earth's equator |
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| Stars within an angular distance from the NCP equal to the observer's latitude are above the horizon for 24 hours |
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| The sun crosses the celestial equator moving southward at the autumnal equinox around September 22 |
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| The apparent yearly path of the Sun through the stars |
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| A division of the year, marked by changes in the weather, ecology, and hours of daylight |
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| The "noon position" is when the Sun is on the meridian on a given day |
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| The farthest northern point above the celestial equator |
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| The Sun crosses the celestial equator moving northward at the vernal equinox around March 21 |
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| The farthest southern point above the celestial equator |
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Definition
| How many degrees above the horixon it is (anywhere from 0 to 90 degrees) |
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Definition
| Causes the Sun's vernal equinox point to slowly shift westward over time, so a star's RA and dec will slowly change by about 1.4 degrees every century (a fact ignored by astrologers), or about 1 minute increase in a star's RA every twenty years |
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Definition
| is how many degrees along the horizon it is and corresponds to the compass direction |
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Definition
| The lines on a map of the Earth that run north-south are lines of longitude and when projected into the sky |
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Definition
| The lines on a map of the Earth that run north-south are lines of longitude and when projected into the sky |
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Definition
| The lines on a map of the Earth that run east-west parallel to the equator are lines of latitude and when projected into the sky |
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Definition
| Occurs when the sun is at its highest point for the day |
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Definition
| The time interval between two successive vernal equinoxes |
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Definition
| Our clocks say that the day is 24 hours long, so the stars move around the Earth in 23 hours 56 minutes |
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Definition
| The time required for the constellations to complete one 360 degree cycle around the sky and to return to their original point on our sky |
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Definition
| It used to be that every town's clocks were set according to their local noon and this got very confusing for the railroad system so they got the nation to adopt a more sensible clock scheme |
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Definition
| When the Earth is at its closest point to the Sun, it moves quickest |
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| When at its farthest point from the Sun, the Earth moves the slowest |
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| The equation of time is the difference between apparent solar time and mean solar time, both taken at a given place (or at another place with the same geographical longitude) at the same real instant of time |
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Definition
| A theoretical Sun that moves along the celestial equator at a constant speed and completes its annual course in the same amount of time the real Sun takes at variable speeds |
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| The moon drifts eastward with respect to the background stars (or it lags behind the stars). It returns to the same position with respect to the background stars every 27.323 days |
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Definition
| (about twice a year) the Sun-Moon angle is exactly 180 degrees and you see the Earth's shadow covering the Moon |
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Definition
| The Moon is in new phase and it is covering up the Sun |
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Definition
| One of the most familiar things about the Moon is that it goes through phases from new (all shadow) to first quarter (1/2 appears to be in shadow) to full (all lit up) to third quarter(opposite to the first quarter) and back to new. This cycle takes about 29.53 days |
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Definition
| An eclipse of the sun in which the edge of the Sun remains visible as a bright ring about the moon |
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| The outer region of partial shadow |
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| Obliquely through the interface between one medium and another or through a medium of varying density |
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| The region of total shadow |
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| The region of total shadow |
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