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THE BIG PICTURE

Each chart below covers a very wide area of sky, roughly from eastern horizon to western horizon. Constellations are green stick figures. The dividing line between constellations are dashed blue lines. The purpose is to show the large scale structure of the night sky: why certain types of objects are visible in certain areas of the sky.1. Above: 6 hr R.A. (Passes overhead on winter evenings): OPEN CLUSTERS are in the sky, north to south (Perseus to Pupis). Open Clusters are generally within the arms of the galaxy and are roughly co-located with the Milky Way. They are plotted as gray circles above. You are looking away from the center of the galaxy, towards the outer rim. (Note: all types of objects are labeled, not just open clusters.)

2. Above: 12 hr R.A. (Passes overhead on spring evening): GALAXIES are in the sky, north to south (Ursa Major to Virgo). They are plotted as blue ovals in the chart above. At 9:00pm during mid-June, the Milky Way is rising in the east. Just to the west of the zenith is the North Galactic Pole, in the constellation Coma Berenices. This means we are looking away from the plane of our galaxy, so our view to other galaxies is not blocked. In Coma Berenices happens to be the heart of the Local Supercluster of galaxies. Many of these galaxies are visible in medium-sized telescopes.

3. Above: 18 hr R.A. (Passes overhead on summer evenings): GLOBULAR CLUSTERS (yellow cross inside a circle) & PLANETARY NEBULAE (purple circle in a cross) are in the sky, north to south (Cygnus to Sagittarius). The lower-middle of this chart is towards the center of the Milky Way galaxy. That is why we see so many globular clusters in that part of the sky. Notice that planetary nebulae populate the Cygnus arm of the galaxy.

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