05/11/2012 – Ephemeris – The bright star Spica
Ephemeris for Friday, May 11th. Today the sun will be up for 14 hours and 40 minutes, setting at 8:59. The moon, 1 day before last quarter, will rise at 2:09 tomorrow morning. Tomorrow the sun will rise at 6:17.
The bright blue star Spica can be found in the southeast as it gets dark now. It’s one of the fainter of the 21 first magnitude stars. It lies in the constellation of Virgo the virgin, and lies very close to the path of the sun, moon and planets in the sky. Saturn is just to the left of it this year. Spica is a binary star, whose brighter component is drawn into an ellipsoid by the tidal effect of the companion. They orbit each other in only 4 days. Spica is 260 light years away and over 3,000 times brighter than the sun. An Egyptian temple at Thebes was oriented to the setting point of Spica. The change in the setting point over time allowed the Greek astronomer Hipparchus to discover the precession of the equinoxes.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Saturn and Spica on May 11, 2012. Created using Stellarium.
05/10/2012 – Ephemeris – The Virgo Cluster (of galaxies)
Ephemeris for Thursday, May 10th. The sun rises at 6:19. It’ll be up for 14 hours and 38 minutes, setting at 8:58. The moon, 2 days before last quarter, will rise at 1:36 tomorrow morning.
The constellation Virgo which contains the bright star Spica and for last and this year the planet Saturn is in a sparse region of the sky as far as stars go. We are almost directly looking out the side of our Milky Way Galaxy. That milky band has been banished to the northern horizon. But while the stars may be few, we are also looking out past a gulf of 50 million light years to a great cluster of galaxies we call the Virgo Cluster. The galaxies here count into the thousands and overflow Virgo itself into Leo to the west, Coma Berenices to the north and Corvus to the south. I found that an 8 inch diameter telescope can pick up the brightest, but that may be my eyesight. Charles Messier spotted them over 200 years ago with a telescope less than three inches in diameter.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Brighter members of the Virgo Cluster. Created using Stellarium. Open circles are galaxies, circles with crosses are globular star clusters, outlying members of our Milky Way galaxy.
Click on image to enlarge.
05/09/2012 – Ephemeris – Where are the bright planets this week?
Ephemeris for Wednesday, May 9th. The sun rises at 6:21. It’ll be up for 14 hours and 36 minutes, setting at 8:57. The moon, 3 days before last quarter, will rise at 12:57 tomorrow morning.
Let’s see what’s happening with the bright planets for this week. Venus is high in the west as it gets dark. Enjoy it now, because it will be gone in 4 weeks. Venus will set at 12:09 a.m. in the west northwest. That’s 19 minutes earlier than last week, so it’s noticeable drawing closer to the sun. Venus is 35.9 million miles away and closing. It is a beautiful brilliant crescent in telescopes. Mars is high in the south in the evening with its unmistakable bright reddish color. It’s in the constellation Leo the lion now. It is 94 million miles from us and moving away. Mars will pass due south at 9:08 p.m. and will be setting in the west at 3:52 a.m. Saturn will be in the southeast just to the left of the bright star Spica. It will pass due south at 12:04 a.m.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Southern sky at 10 p.m. on May 9, 2012. Created using Stellarium.
How to safely view the May 20, 2012 solar eclipse
Note: Parts of this posting are geared to the Grand Traverse region of Michigan wheer the partial eclipse is interrupted by sunset.
May 20, 2012 eclipse from northern Michigan just before sunset. Created using Stellarium.
We get a chance to view a solar eclipse visible for about 40 minutes on the evening of the 20th this month. Solar eclipses are rather rare events if you stay at one spot on the earth. For the whole earth there are at least two or three solar eclipses that occur in a year, and as many lunar eclipses. To see a lunar eclipse one only has to be on the night side to the earth at the time. A solar eclipse requires you to be in the path of the moon’s shadow.
We are getting a chance to see a partially eclipsed sun. Solar eclipses are highly personal events. The exact timing and what you’ll see depends on your location. The society will be holding an eclipse watch at the Sleeping Bear Dunes National Lake Shore lake Michigan Overlook on Pierce Stocking Scenic Drive. In Traverse City, a good vantage point to watch is along the south of east sides of the bays. For both locations the eclipse will start at 8:19 p.m., with the eclipse starting 2 seconds earlier at the Lake Michigan Overlook at 8:19:17 p.m. The sun will set at 9:12 p.m. at the overlook and 2 minutes earlier in Traverse City.
The times I’ve derived for the above is from the website CalSky.com., a not often easy site to navigate. Once you get your location input the calendar feature is very comprehensive.
Solar eclipses or eclipses of the sun, as they are sometimes referred to are listed as three types: partial, total, and annular. Every solar eclipse has a partial phase, where the moon covers only part of the sun. In a total eclipse the moon covers, for a few minutes, the entire photosphere (bright face) of the sun, An annular eclipse is where the moon doesn’t appear large enough to cover the face of the sun, leaving a bright ring or annulus around the moon. This also lasts a few minutes at best.
If you look at your shadow cast by the sun, you’ll notice that the shadow is fuzzy. That fuzzy outer part of your shadow has a name and its called the penumbra. There you are partially blocking the sun’s light. The dark inner shadow is called the umbra, where we get the word umbrella, in which the sun is totally blocked. It just so happens that the moon’s dark umbral shadow just reaches the earth at the moon’s closest.
The May 20th eclipse is classed as an annular eclipse. The area affected by the partial eclipse stretches from east Asia to North America, from the Arctic Ocean to the South Pacific. The path of annularity, where the annular phase can be seen, stretches from south China to Texas. In the United States the annular shadow will cross southern Oregon, northern California, Nevada, southern Utah, Colorado, northern Arizona, cross New Mexico and end in Texas at sunset.
Since the sun is north of the celestial equator, the north end of the eclipse zone stretches farther east than the central or southern parts of the eclipse area. Therefore we will see nearly half of the partial portion of the eclipse. The eclipse map can be found on NASA’s web site here. Select the first entry, and select the May 20th eclipse.
How to safely observe the eclipse
The question with any solar eclipse is: Can I view it safely? The answer is yes, if you take precautions. One gets the impression from all the warnings that looking at the sun during the eclipse is more dangerous than normal. That isn’t true. It’s just not less dangerous. Normally we don’t look at the sun, so we don’t think of it. During the partial phase of the eclipse, its total light is dimmer, but the face of the sun is just as bright and dangerous to look at without proper viewing methods.
The easiest and safest way to view a solar eclipse is with pinhole projection. I tested one a few weeks ago we had a long narrow box about 4 feet long. I put a small hole in one end. It happened to be a 1/8th inch hole, and put a clipboard with a sheet of white paper on the other end and got a respectable sized image of the sun.. On eclipse day I will replace the one pinhole with several of different sizes. The larger the hole the brighter but fuzzier image, the smaller the hole the dimmer and sharper the image.
Pinhole Projection of the sun. Solar image brightened and moon shadow added, however sun diameter is correct.
Various outlets have solar eclipse filters which are made of aluminized mylar which go for about a dollar. They should be safe if used as directed.
Solar filters for telescopes must be placed in front of the objective and not at the eyepiece. These can be obtained from Enerdyne in Suttons Bay, Orion, OPT and other online sources. Order early!. Also remember to cover your finder telescope or get a filter for it too.
The telescope itself can project a large image. See the following image from the 1994 solar eclipse. Use an inexpensive but low power eyepiece in case the sun’s heat damages it.
Telescope projection of the sun. Photo by Eileen Carlisle.
Be safe and have a great time. There’s an even better solar eclipse on August 21, 2017, whose path of totality crosses the United States from coast to coast.
05/08/2012 – Ephemeris – Observing Saturn’s Rings
Ephemeris for Tuesday, May 8th. The sun rises at 6:22. It’ll be up for 14 hours and 33 minutes, setting at 8:56. The moon, 3 days past full, will rise at 12:09 tomorrow morning.
The planet Saturn is a wonderful sight in telescopes now. In a little as 20 power a spotting scope with show Saturn’s rings, but may not distinctly separate the planet out. At 50 power the planet is easily separated from the rings. It you have a telescope with eyepieces of differing focal lengths and/or a Barlow lens that doubles the magnification of your eyepieces, you can experiment with using higher powers. I like a crisp image at lower powers rather than a fuzzy image at higher powers. Saturn’s rings are its best known feature. They are about 170 thousand miles wide and perhaps only a hundred feet thick. They aren’t solid but billions of small icy particles each orbiting Saturn at their own speed, and kept in line by collisions with its ring mates.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Image of Saturn created with Cartes di Ciel showing current ring tilt.
The rings as they appear from earth. The outside ring is the A ring. Then the dark Cassini’s Division, which is sometimes hard to spot. Then the broad and bright B ring. The inner C ring is hard to spot.
05/07/2012 – Ephemeris – The Crescent Venus
Ephemeris for Monday, May 7th. The sun rises at 6:23. It’ll be up for 14 hours and 31 minutes, setting at 8:54. The moon, 2 days past full, will rise at 11:10 this evening.
The planet Venus now is spectacular both to the unaided eye and through a telescope. To the eye Venus is the brilliant evening star in the west in the evening. In a telescope it appears as a bright crescent like the moon. This surprised some of the folks that came out to out star party last Friday. The dark side of Venus is the night side of the planet because Venus is now moving between us and the sun, so it’s shining mostly on the other side of the planet. This effect will get more pronounced as Venus becomes more in line with the earth and the sun over this month. When Venus crosses between the earth and the sun June 5th, our time it will actually pass in front of the sun, a rare transit of Venus that will start a little past 6 p.m. That evening.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
05/04/2012 – Ephemeris – My talk Friday with star party to follow
Ephemeris for Friday, May 4th. The sun rises at 6:27. It’ll be up for 14 hours and 23 minutes, setting at 8:51. The moon, 1 day before full, will set at 5:48 tomorrow morning.
Radio astronomy will be the topic of yours truly this evening at the Grand Traverse Astronomical Society’s monthly meeting at 8 p.m. at Northwestern Michigan College’s Rogers Observatory. This is a rescheduling of a talk that was scheduled for the first Friday in March when we had the big snow storm. Prompted by my recent tour of the National Radio Astronomy Observatory in Green Bank West Virginia, I’ll overview this window on the universe that opened up after World War II. Starting at 9 p.m. will be the monthly viewing night at the observatory. On tap if its clear will be the moon and the planets Venus, Mars and Saturn. The Observatory is located south of Traverse City on Birmley Road off either Garfield or Keystone roads.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
GBT: The Green Bank radio Telescope at The national Radio Astronomy Observatory, Green Bank WV.
Click image to enlarge.
05/03/2012 – Ephemeris – Eclipse cycles
Ephemeris for Thursday, May 3rd. The sun rises at 6:29. It’ll be up for 14 hours and 21 minutes, setting at 8:50. The moon, 2 days before full, will set at 5:11 tomorrow morning.
Eclipses of the sun and moon were most terrifying events for the ancient and primitive peoples. The Chinese thought a dragon was devouring the sun would bang on gongs and shoot arrows into the air to drive the dragon away. It worked every time. Predicting these eclipses became an important matter for ancient astronomers. It was the Chaldeans several centuries before the common era that apparently discovered the interval at which like eclipses occur. The period of 18 year 11 and a third days is called the saros cycle. There are many saros cycles running at any one time. A saros series contains 71 or 72 eclipses, crossing the earth slowly from north to south or south to north. We’ll talk more about eclipses later this month.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
For more information check out Saros in Wikipedia
Saros 136 animation, Public Domain (official work for NASA by Fred Espenak)
Above is an animation of eclipse paths running south to north for saros 136.
05/02/2012 – Ephemeris – Where are the bright planets this week?
Wednesday, May 2nd. The sun rises at 6:30. It’ll be up for 14 hours and 18 minutes, setting at 8:48. The moon, half way from first quarter to full, will set at 4:39 tomorrow morning.
Let’s see what’s happening with the bright planets for this week. Venus is high in the west as it gets dark. Enjoy it now, because it will be gone in 5 weeks. Venus will set at 12:28 a.m. in the west northwest. That’s 8 minutes earlier than last week, so it’s noticeable drawing closer to the sun. Venus is 40.1 million miles away and closing. It is a breautiful brilliant crescent in telescopes. Mars is high in the south in the evening with its unmistakable bright reddish color. It’s in the constellation Leo the lion now. It is 89 million miles from us and moving away. Mars will pass due south at 9:30 p.m. and will be setting in the west at 4:18 a.m. Saturn will be in the east southeast just to the left of the bright star Spica. It will pass due south at 12:33 a.m.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The stars and planets at 9:30 p.m. on May 2, 2012. Created using Stellarium.
05/01/2012 – Ephemeris – The May 20th Eclipse
Ephemeris for Tuesday, May 1st. The sun rises at 6:32. It’ll be up for 14 hours and 15 minutes, setting at 8:47. The moon, 2 days past first quarter, will set at 4:09 tomorrow morning.
(Note: The eclipse visible from most of the United States will be interrupted by sunset. See the Addendum for a link to NASA’s page on the eclipse.)
Let’s give you a heads up on the solar eclipse that will occur on the evening of May 20th. In northern lower Michigan we will see the tail end of the eclipse as the moon’s shadow leaves the face of the earth. The shadow will touch the earth in eastern Asia, cross the Pacific and into North America. This is an annular eclipse, meaning that the moon is too far away to completely cover the face of the sun, leaving a ring (or annulus) of bright sun around the moon at the very center of the eclipse. Some residents of northern California and southern Oregon to west Texas will be able to see this annulus. Your visual safety is paramount when viewing an eclipse and over the next two weeks I’ll be giving you tips on how to view the eclipse safely.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Here’s a NASA Acrobat file detailing the eclipse. http://eclipse.gsfc.nasa.gov/OH/OHfigures/OH2012-Fig01.pdf
Here’s the Eclipses of 2012 NASA page that links to the above page. It has useful links for those, unlike us are located in the southwestern United States.
