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Saturday, May 13, 2017

Astronomy Club Newsletter: The 2017 Total Solar Eclipse

Total Solar Eclipse on August 21, 2017 

Come to our Astronomy Club meeting to find out more about it.

Join the Davis Astronomy Club at Explorit on Saturday, May 13 starting at 7:30pm. We will discuss the what, when, where, why, how, etc. of solar eclipses in general, and of the historical Monday, Aug 21, 2017 total solar eclipse in particular. 

Only viewers fortunate to be in the narrow band across the continental USA - from Oregon coast in the west, where the first sighting will be at 10:15 PDT, to South Carolina coast in the east where, the last land sighting will be 1 hour and 33 minutes later - will experience totality when the sun would be completely obscured by the moon's shadow. Viewers on either side of this narrow band will experience different degrees of partiality. 

  • We will talk about the safest ways to witness this celestial phenomenon.
  • After the discussion indoors, we will have a star party outdoors, weather permitting. 
  • Please bring your telescope and binoculars if you have them. 
  • All meetings of the Davis Astronomy Club are free and open to all ages. Everyone interested is invited. 

For more information, please contact Vinita Domier at 
or call Explorit at 530 756 0191


Great American Total Solar Eclipse of August 21, 2017

by Vinita Domier (

On Monday, August 21, sky watchers across North America will be treated to the rare phenomenon of a solar eclipse. Fortunate observers in the narrow belt spanning the middle of continental USA from west to east will experience a total solar eclipse. For a brief but spectacular moment, day will turn into night as the sun will apparently disappear. Viewers on either side of the band will observe a partial solar eclipse, with the percentage of the sun blockage decreasing for observers further away from the narrow totality region.

The first land sighting of the total solar eclipse will be at 10:15am on August 21 at the Oregon coast, and the last land sighting will be at the South Carolina coast 1.5 hrs later. 

The sun will be partially eclipsed for over an hour before and also after totality, and the maximum duration of totality in the middle of the 115 km band will be 2 mins 40 secs. 

As the Davis/Sacramento region lies south of the band of totality, viewers will observe a maximum of 80% partial solar eclipse that will begin at 9:02am, peak at 10:17am when the sun will appear crescent shaped, and end at 11:39am. 

An eclipse is an astronomical event that occurs when a celestial body is temporarily obscured from view, either by passing into the shadow of another body or by having another body pass between it and the viewer. A solar eclipse can only occur during the new moon phase when the moon is between the sun and the Earth. It is rare phenomenon because the sun, moon, and Earth are not perfectly aligned at every new moon as their orbital planes are slightly tilted with respect to each other.

A total solar eclipse results when the moon’s dark umbral shadow falls on the Earth, briefly obscuring the sun completely for viewers in a narrow band on Earth. A partial solar eclipse is observed when the moon’s less dark penumbral shadow falls on the Earth, resulting in only part of the sun being obscured for viewers in a small area. An annular or ring solar eclipse occurs when the moon obscures most of the sun, leaving a ring visible to viewers in a narrow band. 

It is safe to observe the sky with unaided eyes only during the brief moments of totality, as the sun is completely in shadow. Direct viewing of the sun at all other times must be done using a solar telescope or special eclipse-safe eyewear to avoid permanent eye damage. During a solar eclipse, this includes the time prior to and after totality for observers within the narrow totality path, and for observers in the wider regions on either side of the path experiencing various degrees of a partial eclipse.

For more information, please contact Vinita Domier at

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