Interactive Map Instruction

This interactive Google map shows the path of the Total Solar Eclipse of 2017 Aug 21. The northern and southern path limits are blue and the central line is red. You MUST be somewhere within the central path (between the blue lines) to see the total phase of the eclipse. The eclipse is longest on the central line (red). The yellow lines crossing the path indicate the time and position of maximum eclipse at 10-minute intervals.

 

The green marker labeled GE is the point of Greatest Eclipse. The magenta marker labeled GD is the point of Greatest Duration. This is the location where the total eclipse lasts the longest along the entire path. (The magenta band on either side of the Greatest Duration marker shows a region where totality lasts within 0.1 seconds of the maximum.) In the case of the 2017 eclipse, the Greatest Duration is 2 minutes 40.2 seconds. This prediction does not take into account the mountains and valleys along the edge of the Moon. Detailed predictions using the Moon's limb profile show a corrected value of 2 minutes 41.7 seconds for Greatest Duration. For the sake of speed and simplicity, the effects of the lunar limb profile are NOT used in the predictions and map presented on this page.

 

Note that the central line of the eclipse (plotted in red) is banded by different colors for hundreds of miles east and west of the Greatest Duration marker. The colors correspond to the length of totality (duration of the total eclipse) along different sections of the central line:

  • Magenta - totality lasts within 0.1 second of Greatest Duration (over a span of ~160 miles or ~250 km)
  • Orange - totality lasts within 1 second of Greatest Duration (over a span of ~490 miles or ~790 km)
  • Green - totality lasts within 2 seconds of Greatest Duration (over a span of ~700 miles or ~1100 km)
  • Cyan - totality lasts within 5 seconds of Greatest Duration (over a span of ~1100 miles or ~1800 km)

You can be hundreds of miles from the theoretical point of Greatest Duration and still enjoy totality lasting within a fraction of a second of the maximum possible (as long as you stay within several miles of the central line). It's much more important to watch the weather forecasts a day or two before the eclipse and choose a location with the best chance of a cloud-free sky during the eclipse. Even in Oregon, the total eclipse still lasts 2 minutes. Good weather is the key to successful eclipse viewing - better to see a shorter eclipse from clear sky that a longer eclipse under clouds.

Important Note: The eclipse predictions in this interactive map DO NOT include the effects of mountains and valleys along the edge of the Moon. Such corrections for the lunar limb profile may change the contact times and eclipse durations by ~1-3 seconds. The exact location of Greatest Duration may also change by ~10-20 kilometers.


User Directions

The zoom bar (left edge of map) is used to change the magnification[2]. The four-way toggle arrows (upper left corner) are for navigating around the map. You can also move the map center around to reposition it by holding down the left mouse button and dragging. The two map buttons (top right) let you switch between map view and satellite view.

Click anywhere on the map to add a red marker. A popup window appears above the marker with the calculated eclipse times and duration of annularity for that location (see explanation of Eclipse Circumstances below). The 'x' in the upper right corner of the popup window closes the popup window. Additional markers can be placed anywhere on the map. Move the cursor over a marker to reveal a popup window with the eclipse times for that position. The predictions in the popup window can also be displayed in a new web page via the Eclipse Times Popup button (bottom right). You can select and copy this infomation to paste into a word processor.

 

All the markers can be removed by using the Clear Marker button (below the map). Choose the Large Map check box to produce a bigger map (hint: enlarge the browser window to its maximum size before selecting the Large Map check box). This option is especially useful to users with large monitors.

Below the lower left corner of the map are three readouts. The first gives the geographic coordinates (latitude & longitude) of the map center while the second gives the geographic coordinates of the cursor position. The third line gives the distance of the cursor from the last marker. For more information, see Google Eclipse Map Instructions.

 

Eclipse Circumstances

When you click on the map a red marker is added and a popup window opens giving the Eclipse Circumstances calculated for that location. The predictions in the popup window can be divided into two sections.

In the top part of the window, the decimal Latitude and Longitude of the marker are given. The Eclipse Type (either total, annular or partial) seen from that position is given. The Duration of Totality (or Duration of Annularity) lists the length of the total (or annular) phase in minutes and seconds. The Eclipse Magnitude is the fraction of the Sun's diameter eclipsed. The Eclipse Obscuration is the fraction of the Sun's area eclipsed.

The bottom part of the window consists of a table listing the times for important stages of the eclipse. The Event column lists eclipse phase, followed by the date and time (both in Universal Time). Finally, the Altitude and Azimuth of the Sun is given for each event. The altitude is measured from the horizon (0°) to the zenith (90°). The azimuth is measured from due North and rotating eastward (North = 0°, East = 90°, South = 180°, and West = 270°).

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