Archive
04/11/11 – Ephemeris – First quarter moon
Monday, April 11th. The sun will rise at 7:05. It’ll be up for 13 hours and 16 minutes, setting at 8:22. The moon, at first quarter today, will set at 3:45 tomorrow morning.
Lets take a look at the moon tonight. It’ll be about 14 hours after first quarter and we see features at the terminator, the sunrise line that cuts the moon in half. In small telescopes, at the north or top end of the moon, the wide flat crater Plato has just entered sunlight. Long shadows from its crater walls will retreat across its flat floor. If you look closely you’ll notice that the floor of Plato is slightly convex to conform with the curvature of the moon itself. Nearby is the straight gash in the Alps Mountains, called the Alpine Valley. Supposedly the crater Plato formed shortly after Mare Imbrium formed throwing up the Alps and the Apennine mountains to the south. The Straight wall, another straight feature can be seen on the south end of the moon.
* Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
First quarter moon April 11, 2011 Created using Virtual Moon Atlas
04/08/11 – Ephemeris – Looking out the thin side of the Milky Way
Friday, April 8th. The sun will rise at 7:11. It’ll be up for 13 hours and 7 minutes, setting at 8:18. The moon, 3 days before first quarter, will set at 1:39 tomorrow morning.
In winter and summer we see the Milky Way crossing the sky from north to south. In the autumn we see it cross nearly overhead from east to west. In the spring, especially next month the Milky way is barely visible low in the north. The Milky Way circles the sky as a great circle. It is what we see of our own galaxy. It is a spiral galaxy 100,000 light years in diameter and less than 5,000 light years thick where we are. So in the spring we look out the thin side of our galaxy. The stars are sparser than in other parts of the sky, the constellations generally are larger. The really cool part is that in telescopes we can see other galaxies, other Milky Ways beyond. In the spring we have a huge cluster of thousands of galaxies out there about 50 million light years away.
* Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Looking out the thin side of the Milky Way. Created using Cartes duCiel
This is the entire dome of the sky on May 15th at 11 p.m. Note the Milky Way ringing the horizon. The red dots are galaxies, the blue and gray dots are star clusters in our galaxy, the green ones are nebulae, also in our galaxy.
04/07/11 – Ephemeris – The Ursa Major Association
April 7th. The sun will rise at 7:12. It’ll be up for 13 hours and 4 minutes, setting at 8:17. The moon, half way from new to first quarter, will set at 12:45 tomorrow morning.
The usual impression is to think that the stars of a constellation are actually located close together. This is usually not true. The stars of a constellation can be at vastly different distances. The Big Dipper is different. The five stars, excepting the two end stars of the dipper and 12 other dimmer stars in the general area are of similar distance and have the same motion through space. The group is called the Ursa Major Moving Cluster or Ursa Major Association, and is moving about 9 miles per second relative to us to the east and south. An association is a rather loose, sparse star cluster. This association lies about 75 light years away. If it were five times farther away, it would be the same distance as the Pleiades.
* Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
04/05/11 – Ephemeris – Zodiacal Light
Tuesday, April 5th. The sun will rise at 7:16. It’ll be up for 12 hours and 58 minutes, setting at 8:14. The moon, 2 days past new, will set at 10:45 this evening.
After you spot the moon tonight, hang around outside at the end of astronomical twilight, about 9:37 p.m. look to the west at Taurus the bull and Gemini. Then broaden your gaze. There will be a very faint triangular glow with broad base at the horizon leaning a bit to the left, with its apex near the V of the face of Taurus the bull and the bright star Aldebaran to the right of Orion. This glow is called Zodiacal Light, caused by the reflected sunlight off a cloud of dust located in the plane of the solar system. Most of the large bodies of the solar system orbit the sun close to a single plane. The exceptions to this are comets, which orbit at all angles to the sun and Kuiper belt objects. Zodiacal Light is best seen on spring evenings and autumn mornings.
* Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Back in 1997 I caught the zodiacal light when I photographed Comet Hale-Bopp. This was taken later in April when the apex of the zodiacal glow extended almost to Gemini. Click on the image to enlarge.
IZodiacal Light and Comet Hale-Bopp April 1997. My image.
Here is an enhanced image in black and white.
Zodiacal Light and Comet Hale-Bopp April 1997. Enhanced contrast.
04/06/11 – Ephemeris – The bright planets for this week
Wednesday, April 6th. The sun will rise at 7:14. It’ll be up for 13 hours and 1 minute, setting at 8:15. The moon, 3 days past new, will set at 11:46 this evening.
It’s Wednesday and time again to take a look at the whereabouts of the bright planets for this week. Jupiter is in conjunction with the sun today and will enter the morning sky. It’ll be more than a month before it’s easily spotted in the morning twilight. The ringed planet Saturn is rising before sunset and will be visible low in the southeast as it gets dark. It will cross the meridian due south at 1:37 a.m. and will set at 7:27 a.m. In telescopes Saturn shows its rings which are a year and a half along their seven and a half year opening along with at least one satellite, the large moon Titan. Venus is brilliant in the morning sky and will rise at 6:09 a.m. in the east southeast. It is really a beautiful sight in the morning twilight, though disappointingly small in a telescope.
* Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
04/04/11 – Ephemeris – Saturn at opposition
Apr 4. This is Bob Moler with Ephemeris for Monday, April 4th. The sun will rise at 7:18. It’ll be up for 12 hours and 54 minutes, setting at 8:13. The moon, 1 day past new, will set at 9:43 this evening. | Last night Saturn passed opposition from the sun, that is Saturn was opposite the sun in the sky. That means the earth is nearly directly between them. Also Saturn is at its closest. That’s not as big a deal as with Mars. Saturn, nearly 10 times earth’s distance from the sun, will vary its distance from the earth by plus or minus 10 percent. Not a huge amount. With Jupiter its plus or minus 25 percent. With Mars it’s plus or minus 75 percent. That plus Mars’ eccentric orbit means we only have rare close approaches, every 15 or 17 years. So Saturn appears about the same size no matter were in its orbit or our orbit we see it. We’ll have nearly six months of Saturn viewing in the evening. And Saturn’s the one planet you have got to see in a telescope.
* Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Saturn as seen in April 2011. Created by Celestia.
The above image isn’t a photograph, but was created using Celestia. This is roughly the view of Saturn we see now. Celestia is available free. See the link to the right.
04/01/11 – Ephemeris – Astronomical events in the Grand Traverse area this weekend
April Fools Day, Friday, April 1st. The sun will rise at 7:23. It’ll be up for 12 hours and 45 minutes, setting at 8:09. The moon, 2 days before new, will rise at 6:34 tomorrow morning.
This evening Northwestern Michigan College’s own professor Jerry Dobek will present a talk about the book to be released at the end of this month at this evening’s meeting of the Grand Traverse Astronomical Society starting at 8 p.m. at the college’s Rogers Observatory.. Jerry is republishing A Photographic Atlas of Selected Regions of the Milky Way by E. E. Barnard from the best plates of the 1927 edition with additions and corrections to the original tables. Tomorrow evening starting at 9 p.m. the Society along with the NMC Astronomy Association will host a public viewing night at the observatory. This will be our last chance, if it’s clear to view the setting winter celestial wonders and we’ll get a preview of the rising ones of spring.
* Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
03/31/11 – Ephemeris – The Big Dipper as seen by other cultures
Thursday, March 31st. The sun will rise at 7:25. It’ll be up for 12 hours and 42 minutes, setting at 8:08. The moon, 3 days before new, will rise at 6:13 tomorrow morning.
The Big Dipper is in the northeast nearing overhead at 10 in the evening, it’s seven stars shining brightly. The Big Dipper is not an actual constellation, recognized internationally. It’s part, the hind part, of Ursa Major, the great bear. The Big Dipper is an asterism or informal constellation. It is a distinctly North American constellation. For fugitive slaves, fleeing the southern states in the days before the Civil War, the Drinking Gourd, as they called it, showed the direction to freedom. In England the dipper stars become the Plough, or Charles’ Wain (Charlemagne’s Wagon), In France, known for culinary delights it was the saucepan, or the cleaver. So, other cultures saw what they wanted to see in these seven bright stars.
* Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Big Dipper as seen from other cultures - animation
Big Dipper/Sauce Pan, Plough (plow), Charles’ Wain (Charlemagne’s wagon), and the Cleaver.
03/30/11 – Ephemeris – The bright planets this week
Wednesday, March 30th. The sun will rise at 7:27. It’ll be up for 12 hours and 39 minutes, setting at 8:07. The moon, half way from last quarter to new, will rise at 5:51 tomorrow morning.
It’s Wednesday and time again to take a look at the whereabouts of the bright planets for this week. Mercury is fading fast as its phase becomes a thinner crescent. It’s be a real challenge to spot low in the west after sunset. It would take a pair of binoculars or telescope to have any hope of spotting it. It will set at 9:29 p.m. Jupiter is now too close to the direction of the sun to spot after sunset since it will set at 8:26. The ringed planet Saturn will rise at 8:17 p.m. in the east southeast and will move due south at 2:06 a.m. In telescopes Saturn shows its rings which are a year and a half along their seven and a half year opening. Venus is brilliant in the morning sky and will rise at 6:16 a.m. in the east southeast. It is really a beautiful sight in the morning twilight.
* Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
03/29/11 – Ephemeris – Ursa Major
Tuesday, March 29th. The sun will rise at 7:29. It’ll be up for 12 hours and 36 minutes, setting at 8:05. The moon, 3 days past last quarter, will rise at 5:29 tomorrow morning.
The Big Dipper is now nearly overhead in the northeast at 10 p.m. The seven bright stars are second to Orion in the southwest as the seven brightest stars in a constellation. If you looked up a list of constellations, you’d find that the Big Dipper isn’t there. Ursa Major or the Great Bear is the constellation of which the Big Dipper is a part. The seven bright stars of the dipper is the rump and long tail of this constellation. The rest of the bear, including his head and legs are delineated by dimmer stars. An anatomical problem is its long tail, which was drawn in by the ancients of the old world. The American Indians, also saw a bear in the stars here, but the handle of the dipper became three hunters following the bear.
* Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
My rather crude drawing of Ursa Major, the Great Bear
