Catching Dawn's Early Light



The Pleiades

In Dr. Rayman's September 12th, 2007 Dawn Journal entry , he included a cryptic remark about catching Dawn's early light shortly after launch.

It turns out that as viewed from Hawaii or Alaska, Dawn will appear to pass very close to the Pleiades less than 2 hours after liftoff.

The Pleiades, M45, the Seven Sisters, is an open star cluster that is currently visible in the early morning sky. It is often mistaken for the Little Dipper. It is located in the constellation of Taurus just ahead of Orion.

In his September 21, 2007Journal entry, Dr. Rayman offers more details about this observing opportunity. We hope that observers will be able to get a picture of the Dawn spacecraft tracing a line though the stars!

In general, we know that the Dawn spacecraft will be flying across the sky near the Pleiades. This will favor observers further west in Alaska and Hawaii where it is still dark. We don't know how bright the spacecraft will be and the exact path across the sky will depend on the launch time.

The charts below reflect the trajectory based on the actual launch time 07:34 EDT. Thank you to George Carlisle and Marc Rayman for providing the preview charts and these charts. Please share your images with us (files need to be under 10 MB).

finder_chart   finder_chart

Chart depicting sky for a September 27 Dawn launch that shows Orion, the Hyades and Pleiades: NASA +Enlarge image
Chart for a September 27 Dawn launch depicting region around the Pleiades: NASA +Enlarge image

As Dawn travels around Earth from Florida, it will pass through Earth's shadow and will exit the shadow after it separates from the rocket. And from Hawaii, you'll be able to see it move out of the shadow and into sunlight. To see it, you'll need to go out and start looking before 02:40 HST.

There are two lines shown. These indicate the approximate paths through the sky that the spacecraft will make if it launches near the beginning (top line) or end (bottom) of its launch window.

Find Orion. It will be near the eastern horizon (Hawaii) or southeastern horizon (Alaska). The Hyades and Pleiades will have risen ahead of Orion so they will appear to be more west of it ('above' Orion). The Dawn spacecraft will be a point of light moving from right to left just above the Pleiades or through the Pleiades.

The left image above shows a wideangle view of the sky that includes Orion, the Hyades and Pleiades. You may have to rotate the image counterclockwise to get the graphic to match your horizon, giving you a better idea from which direction the spacecraft will appear.

The right image shows the region around the Pleiades in more detail, depicting what you might see through binoculars or a very low power telescope.

We do not have any indications as to its brightness, but do not expect it to be bright. In fact, from the time marks, it will seem to be moving slowly and that's because it will be far away, which then means it will be fainter.

Launch 01:34 HST
Haleakala, HI Anchorage, AK  
  UTC HST Azimuth Elevation Azimuth Elevation  
  12:50:00 02:50:00 246.3 57.0 208.2 7.9  
  12:55:00 02:55:00 247.4 73.0 201.2 18.3  
  13:00:00 03:00:00 250.9 82.8 195.5 25.9  
  13:05:00 03:05:00 287.4 88.7 190.9 31.3  
  13:10:00 03:10:00 47.8 86.6 187.3 35.3  
  13:15:00 03:15:00 54.2 83.8 184.4 38.3  
  13:20:00 03:20:00 55.7 81.8 182.1 40.6  
  13:25:00 03:25:00 56.0 80.3 180.3 42.5  
  13:30:00 03:30:00 55.8 79.3 179.0 43.9  
  13:35:00 03:35:00 55.3 78.6 178.0 45.2  
  13:40:00 03:40:00 54.6 78.2 177.4 46.2  
  13:45:00 03:45:00 53.8 77.9 177.0 47.1  
  13:50:00 03:50:00 52.9 77.8 176.8 47.8  
  13:55:00 03:55:00 51.7 77.8 176.8 48.5  
  14:00:00 04:00:00 50.4 77.9 177.0 49.1  
Note: Start time is approximately when spacecraft emerges into sunlight from Earth's shadow.

The table above is essentially the same information as the graphics. It tells you what direction to face (azimuth) and how high to look (elevation) at the given times. Azimuth of 0° is due north, 90° is east, 180° is south, and 270° is west.

- See more Dawn Journal entries