Sunday September 27 we experience a total lunar eclipse visible from North America and of course here in San Francisco. This eclipse features the Moon passing nearly through the center of Earth's shadow, meaning that the Moon will remain in eclipse for over an hour and should be fairly dark, at least on one side. And from San Francisco we will see the unique situation of a Moonrise that is of a nearly fully eclipsed Moon, an unusual sight.
Total Lunar Eclipse - geometry
The eclipse takes several hours to occur, from first touch of the Earth's penumbral shadow to last contact, but the main part of the eclipse is the most exciting part, that of 'Totality' when the Moon's surface is fully darkened by the shadow of the Earth. From the west coast, totality starts at 7:13 pm and ends at 8:22 pm. Given that the Sun sets at 7:01 pm, the local conditions should lead to a very interesting Moonrise (just moments after the sunset) with nearly all of the Moon eclipsed.
The San Francisco Amateur Astronomers (SFAA) will be set up at Pier 15 along San Francisco's Embarcadero (just next to the Exploratorium) for public viewing, as the rising Moon should make a lovely picture just above Treasure Island and the San Francisco Bay. We will be there from 6:30 until 8:30 pm.
Here are several excellent resources on the eclipse:
The dawn sky is punctuated this week with a spectacular
lineup of some of the brightest celestial objects in the heavens. The waning
crescent Moon is the centerpiece of the eastern horizon in the hour before
sunrise, shimmering next to Venus, currently a blazing gem of a ‘morning star’
due east, piercing the darkness of the horizon well before the first light of
day, and remaining brilliant until the glow of sunrise washes out the planet.
Fall is a great time for seeing the morning sky since the
days are getting shorter and the darkness lingers longer each morning, giving
early risers like me a chance to get in some astronomy before starting my day
in earnest. Each morning this week as I step out of my front door facing east,
I await the spectacle of some of the brightest stars in the entire night sky
and the wandering visitor Moon this week, taking the stage with Venus to amaze
me and all who take a moment to savor this sight.
Late Summer is a time when the heat waves set in, giving
everyone a last taste of the warmth that longer days and warming landscapes
bring. However, as Earth approaches the Autumnal Equinox, the days are becoming
noticeably shorter as sunrises arrive later in the morning while sunsets arrive
earlier in the evening. The dual effect is most pronounced around the time of
the Equinox, as the amount of time the Sun spends above the horizon shrinks
most rapidly in this period.
Change of the Season
Every day throughout the year, the time of sunrise or sunset
changes slightly, extending the number of hours of sunlight from December until
June, and reversing course from July until December again. However, the
mid-points of this gradual change are the Equinoxes, the point at which the
change is at its greatest (tip for the mathematically inclined: it is the
maximum point of the first derivative of the duration of the day, a sine wave
that is passing through an intercept J).
What does this feel like? Take note of this for the coming
weeks as you experience your daily routine, and notice the time when brightness
arrives in you morning and when darkness sets in each evening. The change is
quite pronounced, with the amount of daylight diminishing by up to 30 minutes
in a single week in mid-September, at mid-northern latitudes as we have in San
Francisco. If you are located further north in latitude (Canada, Northern
Europe) the effect is even more pronounced, with up to an hour in a single
week! I find this fascinating and marvel every year at the dramatic changes
that we all take for granted in our environment. Fall is indeed a season of great
change. Savor the moments.
In 2005 I began writing a column for the San Francisco Waldorf School newsletter called "The Urban Astronomer." I started this blog in 2007 as a place to archive my articles and to offer additional insights on the night sky - even if you live in a big city. In 2008 I became an occasional guest on the KFOG Morning Show, and more recently on KALW and KGO. Archived shows are posted on the blog. I conduct private star parties for special events and corporate events. Contact me for details.