A sky map is exactly what the name implies, it is an accurate, detailed visual image of space and the objects that are in space, as far as we can see with our latest technology. The earliest sky maps depicted constellations that were visible to the naked eye at night, associating them with familiar objects. Although the earliest sky maps are so old that they are depicted in cave drawings, Western civilization bases it's understanding of the Northern Hemispheric skyin the contexts established in Greek mapping and mythology. The current official setup of sky maps involves the determination of the International Astronomical Union that there are 88 official constellations that have distinct boundaries. The totality of constellations makes up the entire sky map.
One of the best ways to enjoy a sky map is to use Google Sky, an incredibly rich compilation of space photographs that are stitched together to give a view of every one of the 88 constellations in a variety of formats, including simple photographs, microwave, infrared, and historical. Google Sky has special views of the most familiar 12 of the 88 constellations, including Aquarius, Gemini, Leo, and so on. By downloading Google Earth, you can view the Earth and Google Sky.
In order to create Google Sky, the worlds largest observatories worked in teamwork with the Google Earth platform and with enhancements from the Hubble telescope to create a comprehensive map of the entire sky. The Sloan Digital Sky Survey, the Digitized Sky Survey, and the Hubble were used to create a "mosaic" of images that will show what is going on in real time every night! The planets can be brought up, as well as the constellations and Hubble highlights.
The Mercator Projection is used to lay out the Google Sky map, with a warning that this projection has blind spots at the North and South celestial poles on this map. The Mercator projection is essentially a cylinder with nothing at the top and bottom, where curved lines are straightened out. This form was developed for nautical charts.
The Infrared Astronomical Satellite (IAS) was used to creat the infrared version of the sky map. This allows a new view of the sky to see what the infrared spectrum has to say. NASA's Wilkinson Microwave Anisotropy Probe (WMAP) shows what happened an estimated 380,000 years after the Big Bang. The historical version shows the sky as drawn by Giovanni Maria Cassini, circa 1792. It shows the constellations in a classical artistic form.