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Asteroid Gaspra
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The Horsehead Nebulae
| Conjunction | A superior planet is "in conjunction" when it is on the opposite side of the Sun from the Earth. A superior planet cannot have an inferior conjunction. |
| Declination | The equivalent of Latitude on the Earth. Declination is measured in degrees North and South of the celestial equator. |
| G.M.T. | Greenwich Mean Time (GMT) is the time measured on the Earth's zero degree line of longitude, or meridian. This runs from the North Pole to the South Pole, passing through the Old Royal Observatory in the London suburb of Greenwich. |
| Latitude | This tells us how far North or South of the equator we are, here on the Isle of Skye at Dunvegan we are 57 degrees 26 minutes North of the equator. |
| Longitiude | This tells us how far East or West of the Greenwich Meridian we are. The Grenwich meridian is an imaginary line running from the North Pole, through Greenwich and to the South Pole, around the other side and back to the North Pole. This is set at 0 degrees Longitude. In Dunvegan we are 6 degrees 34 minutes West of the Greenwich Meridian. |
| Magnitude | A way of measuring the brightness of a star or other body: the lower the objects magnitude value, the fainter it appears in the sky. A star of magnitude +5.0 is quite faint to the human eye and therefore requires a dark sky to be able to see it, while Sirius in the constallation Canis Major has a magnitude of -1.4, the brightest star in the Sky and is easily seen. |
| Occultation | An event whereby one astronomical body is obscured by another, the most obvious example of this is a Solar Eclipse which is where the Moon covers the disk of the Sun. In Lunar Occultations this is the Moon covering up a star. |
| Opposition | A superior planet is at "opposition" when it is on the opposite side of the Earth from the Sun. This is generally the closest it comes to the Earth and the time at which it is most easily visible. |
| R.A. | Right Ascension is the equivalent of longitude on the Earth but projected in the night sky. 0 degrees RA starts at the first point of Aries or the vernal equinox, this is where the Sun crosses the celestial equator in March. |
| Superior Conjunction | This is when an inferior planet (Mercury or Venus) is on the far side of the sun, so is not visible. |
| U.T. | Universal Time - The mean solar time for the meridian at Greenwich, England, used as a basis for calculating time throughout most of the world. Also called Greenwich time, Greenwich Mean Time, Zulu time, UT1. |
| Zenith | This is the direction directly above the observers location. |