The apparent position with respect to the true equator and equinox of date are corrected for precession, nutation, and aberration of light in addition to proper motion and parallax. When the time is between 3000 BC and 3000 AD, positions of the stars with respect to J2000.0 mean equator and equinox are corrected for proper motion and annual parallax. The popup box shows further information about the star. Stars in the charts can be clicked and a popup box will appear. However, it should be noted that stereographic projection is not designed to model the Moon illusion. This feature might not be as bad, since constellations do appear bigger when they are close to the horizon because of the Moon illusion. This effect is quite noticeable in animations showing the diurnal motion of the sky. For example, a constellation is about twice as big when it is near the horizon than when it is near the zenith. However, the mapping does not preserve area. The mapping is conformal and shapes are preserved over a small area. Stereographic projection is commonly used in sky maps. The star charts are created using the stereographic projection with the nadir as the projection point. When the Day/Night button is active, the background color of the star chart is determined by the Sun's position in the chart: light purple when the Sun is above the horizon, gradually changes to black when the Sun is below the horizon and black when the Sun is 18° below the horizon. The full names of the constellations are listed on this webpage. Sidereal times and star charts at other locations and times can be obtained by clicking the Locations and Times button at the top of the page and filling in the form.Ĭonstellation labels, when active, are shown in the abbreviated form. The two default locations are at longitude 88.2434°W, latitude 40.1164°N (Champaign, IL, USA) and at longitude 88.2434°W, latitude 30°S. This webpage uses the computer's clock to obtain the current local time and then uses it to calculate the local sidereal times and plot star charts on two locations.
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