This puts all the definitions in one handy place!
Sacred Hoop The outside ring of the Sacred Hoop is a circle of stars including Pollux, Castor, Capella, the Pleiades, the Hyades, Rigel, Sirius, and Procyon. These are all prominent stars forming what astronomers refer to as the Winter Hexagon. The Lakota and other native tribes refer to this area of the sky as the Sacred Hoop. This circle of stars is intersected by the Ecliptic (the plane of the solar system) and the Milky Way (the plane of the galaxy) creating a crossing of these two planes through the middle of the Sacred Hoop resembling the Native American Medicine Wheel.
The place of the intersection is between the feet of the Twins and the horns of the Bull. There is only one time in 26,000 years that the exact placement of the June solstice (0 degree Cancer) can fall on this intersection. It is happening now located near galactic anti-center (the opposite of Galactic Center) looking out into deep space. One definition of the Sacred Hoop is…The four directions, the four quarters with the full power of the earth and sky and all related life is regarded as the Sacred Hoop. http://www.think-aboutit.com/
Celestial Sphere is the imaginary sphere around the Earth. Or said another way if we imagine the Earth as a sphere and project that into space all that is contained within that sphere is the Celestial Spere or our known universe. More on the Celestial Sphere.
Celestial Equator is the Earth’s equator expanded into space.
Celestial Longitude for astrological purposes is the distance measured in degrees between the first point in the zodiac (O degrees Aries) and any celestial body, measured along the ecliptic (the plane of the Solar System and the path the planets travel). Or said another way the zodiacal postitions of the planets and stars from the Earth’s perspective. Longitude is a one dimensional way of locating a celestial body from the Earth.
Declination is the angular distance north or south from the celestial equator. Declination gives another coordinate for locating stars and planets in space and is measured east and from the Meridian of Greenwich. Here is a great article about declination and longitude.
Additional Note: Both longitude and declination have 360 degrees that form a grid locating objects in space in relationship to the Earth.
Galactic Plane or the plane of the Milky Way Galaxy visible as the think band of stars of the Milky Way
Ecliptic or the plane of the Solar System and the path the planets travel.
Galactic Cross where the plane of the galaxy (the Milky Way) intersects with the plane of our Solar system also known as the ecliptic.
Galactic Center is the center of our Galaxy near a Galactic Cross located between the constellations of the Scorpion and the Archer.
Galactic Edge is the edge of our Galaxy located near the other Galactic Cross located between the Horns of the Bull and the Feet of the Twins. Also defined as the point on the celestial sphere diametrically opposite to galactic center.
Equinoxes are points located in the sky where the plane of the Solar System intersects with the Celestial Equator. When the Sun reaches these points there is a balance or equal number of hours for day and night. These points move backward one degree every 72 years making one complete circuit about every 26,000 years.
Solstices are points located in the sky where the plane of the Solar System and the Celestial Equator are furthest apart. When the Sun reaches the Winter Solstice we have the shortest day and longest night. When the Sun reaches the Summer Solstice we have the longest day and the shortest night.
Apogee is when the Moon or another planet is furthest away from Earth in its cycle
Perigee is when the Moon or another planet is closest to the Earth in its cycle
Perihelion is when the Earth or another planet reaches its closest approach to the Sun.
Apehelion is when the Earth or another planet reaches its furtherst point away from the Sun.
Lunar Standstill is when the Moon reaches its maximum declination of almost 29 degrees North or South of East and West. The center point of this occurs every 19 years when the North Nodes is 0 Aries and the South Node is 0 Libra.
Syzygy generally refers New and Full Moon times when the Sun, Earth, and Moon are aligned. Although a syzygy also is applied to the alignment of three planetary bodies. A syzygy occurs whenever an observer on one of the three objects (in our case the Earth) sees two other objects either in opposition (when they are 180 degrees apart) or in conjunction (when they are together). The most dramatic expression of a syzygy occurs when we have a Solar and Lunar eclipse.
Solar Eclipses occur during New Moon times when the Sun, Moon and Earth are so perfectly aligned the Moon is passing between the Sun and the Earth blocking out the Sun.
Lunar Eclipses occur during Full Moon times when the Sun, Moon and Earth are so perfectly aligned the Earth passes between the Sun and Moon and the Earth’s shadow is seen on the face of the Moon.
Occultations are a type of eclipse that occur during syzygy when from the Earth we see the Moon passing in front of a planet. A Moon occultation of a star by the Moon does not qualify as syzygy, since the star is far beyond the limits of the solar system.
Star Magnitudes (or visibility) lessens as the number increases. For example, a first magnitude star is one hundred times brighter than a sixth magnitude star and a sixth magnitude star is barely visible to the naked eye. Venus can reach as high as -4.6 magnitude the very brightest planet or star in our night sky. The Full Moon is -12 magnitude and the Sun is a -27 magnitude. Sirius is the brightest fixed star in our sky and is visually rated as a -1.42 magnitude. The magnitude system was established by Hipparchus and Ptolemy (21 First Magnitude Stars coming soon)