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You need to specify two locations to get a chart. One location is your "source point" -- the point in space you're viewing the sky from. The second location is your "target point" -- the point in space that the chart centers on.

Each location has a preselected list of stars to choose from, which contains all common named stars (such as Polaris or Sirius) as well as a selection of relatively nearby stars (such as α Centauri and 61 Cygni). If you want to use one of these stars, just select it from the list.

If a location you want to use isn't in the list, you can enter a variety of location types directly into the text field next to the list.

Valid entries for the free-text field include:

Type Format examples

Celestial coordinates in degree/minute/second format (2 or 3 numbers per coordinate)

Right ascension, declination, and (optional) distance in light years. Separate the components of each coordinate with at least one space, and the coordinates themselves with commas. If the distance is omitted, the position will be treated as infinitely remote.

Labels for the coordinates (like "hr", "min", or "°") are allowed, but will be ignored when the coordinates are entered. The final value for the location depends strictly on the numbers entered, and their order.

12hr 0min 30.5sec, 45deg 22min 11sec

12h 0m 30.5s, 45° 22' 11",3500

Celestial coordinates in decimal format (1 number per coordinate)

Right ascension, declination, and (optional) distance in light years. As with degree/minute/second format, separate coordinates with commas, and a missing distance is treated as infinitely remote.



Common star catalogs

Valid catalog IDs: "HIP" (Hipparcos), "HR" (Harvard Revised), "HD" (Henry Draper) and "Gl" (Gliese)

HIP 123, Gl 456, HR 789

Greek letter and Flamsteed number star labels

Use a Unicode Greek letter or an English spelling of the Greek letter name, and the 3-letter constellation abbreviation. For superscripted numbers, use a dash plus the number after the Greek letter.

β Cyg, beta Cyg, π-3 Ori, Pi-3 Ori, 61 Cyg

Proper Names

These include stars with well-known names, as well as a few uncommon catalog IDs that are rarely used except for a small number of nearby stars.

Polaris, Betelgeuse, Barnard's Star, 82 G. Eri, Lalande 21185

Chart settings

Chart Magnification: By default, the chart displays an area approximately 60° wide. Using a higher magnification gives you a smaller displayed area, in inverse proportion to the magnification. For example, a magnification of 6 gives you about a 10° field of view.

Chart Size: This is the width of the chart in pixels. The Distant Worlds Star Mapper will automatically choose an appropriate height (normally 3/4 the width). The default value, 1000, is appropriate for small-to-medium size modern displays.

Label stars brighter than magnitude: Specify the apparent magnitude of the faintest stars to show. Larger values give more details (fainter stars), but also take longer to plot.

Label stars closer than: Stars closer to the viewing point than this value will be labeled in orange text.

Years before or after epoch (2000.0): By default, the stars are shown as they appear at the beginning of the year 2000. Over time, the stars' natural motion significantly changes the appearance of the sky. The effect is negligible for all but the fastest-moving stars during a human lifetime, so as of the current date (early 21st century), for most views you can ignore this setting. To explore the appearance of the sky over hundreds or thousands of years, enter a non-zero number in this field. Enter a positive (for future) or negative (for past) number to examine the sky at a different time.

Note for the technically-minded: This setting applies a proper motion and radial velocity calculation, but does not attempt to correct for precession (especially since you can have a viewpoint far from Earth, making precession irrelevant). If you turn on the constellation boundaries or coordinate lines (see "Chart Labels"), they will always be drawn in their positions for 2000.0. It also assumes the velocities of the stars are constant, moving in straight lines, so this setting will be very inaccurate after several hundred thousand years. Eventually, at very large times past or future, all the stars fly away, never to be seen again. Calculating stars' orbits around the galaxy is beyond the scope of this application.

Chart Labels

Show R.A. and Dec. lines: Draw a grid of right ascension and declination lines on the chart. The grid will only appear for views at, or fairly close to, the Sun.

Show constellation boundaries: Draw the official constellation boundaries on the chart. As with coordinate lines, the boundaries will only appear in views fairly close to the Sun.

Abbreviate Bayer/Flamsteed designations: By default, a Bayer (Greek letter) or Flamsteed label includes the constellation abbreviation (e.g. 61 Cyg). If you're looking at a small area within a constellation, or if there are many stars labeled, the constellation label many not be desired. The "Abbreviate" setting disables it, so 61 Cyg becomes just "61".

Show all common names: By default, only stars brighter than the "Label stars brighter than..." setting get labeled. This setting causes all stars with a common name or a Bayer or Flamsteed designation to be labeled, regardless of mangitude.

These first four settings, if all enabled, produce a view very similar to a typical star atlas chart.

Identify Sunlike stars: When enabled, this setting causes all stars within a certain luminosity range (currently 10% to 200% of the Sun's) to be labeled, in bright yellow text.

Check to use Tycho-2 data: This setting enables the Tycho-2 database of over 2 million stars, or about 20 times more than the base Hipparcos catalog. When enabled, stars down to 12th magnitude can be shown. The tradeoff: there is no distance information for Tycho-2 stars, so the only available source location is the Sun. Any other location you select under "Source" will be ignored. Additionally, Tycho-2 data is only available at high magnifications (10 or higher).

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