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Charts Help

Getting Started

You start off in "Atlas" mode. This gives you a moderately detailed star chart centered on the default target (the constellation Orion) as seen from the Sun (Sol).

To recenter the chart on something else: Type the name or catalog ID of a star or other object you wish to see -- such as "Polaris" or "Messier 31" -- in the "target" field (the right text box). Then either hit Enter or click "Redraw". This recenters the chart on the selected target. Once the chart redraws, you can then use the navigation tool to move the chart a small distance in one of the 4 major directions.

To get details about any object on the chart: Just click its symbol when the object's name or ID appears on screen. Detailed information will then appear for that object. Click its symbol again to hide the details.

To recenter the chart on an object whose details are visible: Click the "Recenter" (crosshair) icon in the object's details.

To see the sky from another star: Enter that star's name as the "target" and either hit Enter or click "Redraw". Alternatively, for many stars, you can go directly to that star by clicking the "Go To..." (rocket) icon in that star's details when the details are visible.

To get back to the Earth from any other point in space: Click the Earth icon in the navigation tool, or the Earth icon in any object's details near the object name.

Chart Actions

Main Control Bar

This appears at the top of the chart, and controls most chart functions.

Icon Action Description
Screen Mode Toggles between regular mode (main web site layout) and full-screen mode.
Change Chart Type Choose from one of several 'prefab' chart settings.
Increase Chart Size Create the same chart in a larger area.
Decrease Chart Size Create the same chart in a smaller area.
Zoom In Increase the chart magnification.
Zoom Out Decrease the chart magnification.
More Stars Increase the number of stars shown.
Fewer Stars Decrease the number of stars shown.
Labels Switch various chart labels on or off.
Advanced Change more complex (or less-often used) chart settings.
Download Download a copy of the current chart.

Navigation Controls

This appears in the upper-left corner of the chart, and enables chart location changes without entering a specific location or target.

Icon Action Description
Back to Earth Set the source location to the Earth. Same function as the Earth icon in the star/DSO details.
Up Increase chart center declination/altitude ("look up")
Down Decrease chart center declination/altitude ("look down")
Left Increase chart center right ascension/azimuth ("look left")
Right Decrease chart center right ascension/azimuth ("look right")

Star/Object Detail Controls

These appear when you select a star or deep-sky object and view its details.

Icon Action Description
Additional Information If present, you can click this icon to launch an information page (generally from Wikipedia) about this object in another tab/window.
Center on Star/Object Set the target location to this object. This leaves your source location unchanged.
Go To Star* Set the source location to this object. This leaves your target unchanged.
Back to Earth* Set the source location to the Earth. This leaves your target unchanged.
Zoom In** Deep Sky Closeup mode
Zoom Out** Deep Sky Wide Field mode

* Stars only. The Go To Star option only appears for stars with an entry in the Hipparcos catalog. Back to Earth only appears if you are viewing from a location far from the Earth (i.e., well outside the boundaries of the solar system).

** Deep-sky objects only. In Closeup mode, the chart "zooms in" on the selected deep-sky object until the chart scale is exactly the same as the scale for the DSO image from the Digital Sky Survey. In Wide Field mode, the chart scale is the same as a medium-magnification Atlas chart.

Other Options

To get a selection of other chart types, like very wide-field (naked-eye) views, or charts styled similarly to classic printed atlases like Uranometria, choose a different chart mode from the Chart Types menu.

To travel to a distant star, and see the sky from that star, either enter the star's name in the "Location" field, or click the "Go To Star" icon in the star's details. To get back to the Earth, hit the "Earth" icon in the navigation tool or in any star's details.

To customize chart labels (like coordinate grids and deep-sky objects), options, click "Labels" to show the list of options. Changes to labels take effect immediately when selected or unselected.

To customize more advanced settings, click "Advanced" to reveal the settings, or select a "Custom" chart in the chart menu. Then change what you want and click "Redraw".

To save an image file (.png) copy of your chart, click the "Download" icon.

About Charts, Locations, and Sizes

The Chart Types menu enables various "prefab" chart settings.

  • Atlas: Charts in several detail levels with medium to high magnitude limits, celestial coordinates marked, and constellation boundaries identified.
  • Naked Eye: Several charts with very wide image scales, low magnitude limits, and fewer labels. For more details, see the Naked Eye help page.
  • Classic Star Atlases: These settings mimic the layouts and fields of view of famous printed star atlases such as Sky Atlas 2000, Uranometria, and the Millennium Star Atlas. For more details, see the Classic Star Atlas help page.
  • Telescope: High-magnification fields offering detailed views of deep-sky objects.

The Location (left text box) and Target fields (right text box) let you specify where you're viewing from (the 'Location') and where the chart is centered (the 'Target'). You can enter a star or deep-sky object by name or catalog ID, a constellation name, or an exact 3-D coordinate value. For format details, see Location Formats.

To update your chart with any updated settings, click "Redraw".

Chart Labels

Chart label options appear when you click the Labels icon. Any changes to the labels take effect immediately once they are selected or unselected. When you change a label, the chart type changes to "Custom", to let you know that the setting is different from any of the existing "prefab" options.

General label options:

  • Coordinate grid: Turns the right ascension/declination grid on or off.
  • Constellation names: Turns constellation names on or off. At wide scales, this puts names near the centers of the constellations. At medium to high chart magnifications, the names identify the constellations occupied by the chart center and the four chart corners.
  • Constellation lines: Turns the official constellation border lines on or off.
  • Star names: Turns common star names (like Sirius or Polaris) on or off.
  • Star catalog IDs: When enabled, all "classic" star catalog designations (Bayer Greek letters, Flamsteed numbers, proper names, and variable star designations) will appear, regardless of any other chart label settings.
  • Abbreviate IDs: By convention, Bayer, Flamsteed, and variable star designations normally include the constellation abbreviation (e.g. δ Cep, 61 Cyg, R CrB). If you're looking at a small area within a constellation, or if there are many stars labeled, this may not be what you want. The "Abbreviate" setting disables the constellation abbreviations, so a label like "61 Cyg" becomes just "61".

Star label options:

  • Deep-sky objects (DSO): Enables deep-sky objects (galaxies, clusters, etc.). Click an object's symbol to reveal extra information.
  • DSO Images: When DSOs are shown, and this option is enabled, selecting a deep-sky object will find its image in the Sloan Digitized Sky Survey (when available) or the Palomar Observatory Digitized Sky Survey and display it near the DSO's symbol.
  • Sunlike stars: When enabled, stars similar to the Sun in spectrum and luminosity will be labeled specially (bright yellow text).
  • Nearby stars: When enabled, all "nearby" stars will be labeled with the star’s distance, in light years, as part of their label (e.g. "Sirius (9 l.y.)"). "Nearby" stars are defined on a per-chart basis and are usually under 50 light years for wide-field charts and 100 or 200 light years for ones at higher magnifications. The exact cutoff is in the Advanced Chart Settings under the "Label stars closer than" setting.
  • Motions: When enabled, and a non-zero time frame for stellar motions is set in the Advanced Chart Settings, markers showing stellar motion are drawn.
  • Variables: When enabled, variable stars are identified with a circle around the usual star symbol, and labeled with their name or catalog designation.

Advanced Settings

These are normally hidden. To reveal them, click the "Advanced" icon.

  • Chart Projection: Change the chart projection type. For more details, see the Chart Projections page.
  • Double-click options: When you click once on a star or DSO, you get additional information about that object. Normally, clicking a second time dismisses the extra information display. This is the default behavior.


    If you want double-clicking to recenter the chart on the selected object, select "Recenter chart on selected object".

    If you want double-clicking to travel to the selected object, select "Go to selected object". Be aware that this option only works for stars with a known distance -- it is inactive for all deep-sky objects and for faint stars from Tycho-2 or UCAC-4.

    If one of these options is active, the corresponding icon ("target" for recentering, "rocket" for traveling to something) will not appear in the object's detailed information.

  • Chart Size: Pick the chart's width in pixels. Its height will be set automatically based on the aspect ratio (also in the Advanced settings).
  • Chart magnification: At a magnification of 1, 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.
  • Aspect ratio: Controls the ratio of chart width to chart height.
  • Chart magnitude limits: These change the magnitude range for both stars and deep-sky objects. Larger values give more details (fainter objects), 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.
  • Chart time (years before or after 2000): 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 stellar proper motion and radial velocity calculations, but does not attempt to correct for precession -- especially since you can have a viewpoint far from Earth, making precession irrelevant. (For the really technically-minded, the epoch for Endeavour is whatever year you specify, but the equinox is always 2000.0.) If you turn on the constellation boundaries or coordinate lines (see "Chart Labels"), they will always be drawn in their positions for 2000.0. Endeavour 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.

  • Stellar motion markers (years before or after chart time): Controls the length of the stellar motion markers. Each marker represents the amount and direction of motion of the star over the time frame, in years, specified for this setting. Negative numbers correspond to years before the chart time, and positive numbers to years after.

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