November 18, 2017

Astro-Event: A Fine Total Lunar Eclipse.

Our photo of last December’s total eclipse.

Mark your calendars; this Saturday, December 10th a total lunar eclipse graces our fair planet, and a good swath of humanity will get to see it. This particular eclipse occurs at sunset/moonrise for observers in central Europe, the UK, and north-eastern Africa westward, and just before sunrise/moonset for all of North America except the U.S. eastern seaboard and the Maritimes. [Read more...]

AstroEvent(s): A Conjunction, a Perihelion, a Meteor Shower & an Eclipse…

A Partial Solar Eclipse seen from Davis-Monthan Air Force Base, Arizona. (Photo by Author).

   2011 is here; let the astronomy events begin! And a what a busy first week of January it is; right out the gate, we have no less than four significant events to talk about; [Read more...]

Astro Event: A South Pacific Eclipse.

Animation of the July 11th Solar Eclipse. (Credit: A.T. Sinclair/NASA).

Path of the solar eclipse…click for animation. (Credit: A.T. Sinclair/NASA).

   This year’s big ticket astronomical event occurs over a sparsely populated but beautiful track of our planet; we’re talking about July 11th’s total solar eclipse. Of course, it isn’t often that an eclipse doesn’t occur over the windswept Arctic or a war-torn banana republic… the Sun and sand of an island eclipse may just be the perfect combo. If you haven’t already made plans to catch one of the numerous cruises headed that way you may have to enjoy it vicariously with the rest of us via the Internet; this eclipse graces only a smattering of islands before making a brief landfall in South America across the Chilean-Argentine border at sunset. The path of solar totality will not grace our planet again until November 2012 in another South Pacific eclipse that intersects this month’s path! Its maximum length of 5 minutes and 20 seconds occurs over open ocean. Two very interesting sites for viewing include Easter Island and just off of the coast of French Polynesia and Tahiti; the more adventurous may want to head for the Cook Islands site of Mangaia, which lies right along the centerline. Weather prospects may favor the northern hump of the path, with a mean cloudiness of less than 50%… but for sheer beauty and landscape photo ops, Easter island will be your best bet. No doubt most of humanity will experience this one vicariously via the web; follow @Astroguyz via Twitter, as we’ll post where online to watch this extra-ordinary event in the days leading up to the eclipse!     

The Astro-term for this week is Metonic Series. A metonic series of eclipses arises from the fact that the period of 19 tropical solar years is very nearly equal to 235 synodic months. This was first recognized by the astronomer Meton of Athens in the year 432 B.C. The error of difference is 2 hours per 19 years, and this accumulates to a full calendar day every 219 years. A metonic cycle of eclipses will share the same calendar date in groupings of 4 to 5 per series… for example, the first eclipse related to this month’s was on July 11th, 1953 and the last will be 19 years from now, on July 11, 2029. Do not confuse metonic series with saros cycle, which is independent of the solar calendar and based on a period of 223 synodic months. So what, you say? Well, metonic series not only factor into eclipses landing on the same date, but also play a role in calculating when the Moon will appear at the same phase in the same position again… metonic series even play in to trajectory calculations for lunar bound spacecraft, as well as serving as a basis for the Hebrew calendar and the computation of Easter!

AstroEvent of the Week: A Solstice/Lunar Eclipse Tie-In.

Hudson-henge! (Photo by Author).

Hudson-henge! (Photo by Author).

 

   Astronomers and lovers of the dark rejoice; Monday we take begin to take back the night! The summer solstice occurs June 21st at 11:28UT; this is the point that the Sun is at its highest apparent northerly declination and begins its long march southward. If you’re down under, of course, it’s the beginning of winter and the reverse is true. You probably won’t notice the slow creep of darkness and ever shortening days until around September, but it’s the thought that counts. The higher northerly latitude you are, the greater the variation. And to top things off, a partial lunar eclipse occurs on Saturday, June 26th. This will be visible from the Far East at moonrise eastward across the Pacific in its entirety to North America at moonset. Only the northeastern US gets left out. This will be the first lunar eclipse over the contiguous US since February 2008, and at its maximum the Moon will be 54% eclipsed. First contact with the umbra occurs at 10:16UT and the Moon departs the umbra at 12:59 UT. This eclipse is part of saros series 120, and sets the stage for the Tahitian total solar eclipse next month. This is also a good primer for December’s total lunar eclipse, which will occur in its entirety over the US on the winter solstice!  

The Astroword for this week is Gnomon. Ever wonder what that protractor-looking arm is called on a sundial? Of course you have, and now you can tell people with authority that this is known as a gnomon, complete with the silent “g”. Gnomon is Greek for “indicator” or “one who discerns”, although the phrase “she was the gnomon for all which was a failure in my life,” might be stretching it a bit. For a sundial to work function properly, the gnomon must be set parallel to the Earth’s axis, which is a fancy way to say to the north in the northern hemisphere and south…well, you get the idea. Hopefully, this knowledge won’t spark a lawsuit against the Ancient Greeks by any manufacturer of polar aligned telescopes. Now during the summer solstice is a good time to check that garden sundial against your local standard solar transit time or measure the sun fast as evinced by our friend, the equation of time… gnomon also makes a good “gn” Scrabble word, right along with “gnarled” and “Gnostic,” a sure fire way to get folks scrambling for the dictionary!

Event of the Week: A “Blue Moon” Eclipse!

This New Year’s Eve rounds off the calendar with an especially rare treat, although its one that not everyone will get to witness; a partial eclipse of the full “blue” moon. The second full moon of December, the first occurred on December 2nd of this month. This eclipse, however, is extremely shallow; at maximum, the moon will only be 7.63% immersed in the dark umbra of the earth’s shadow.

[Read more...]

29.10.09:Is Solar Activity on the Upswing?

Our characteristically dormant Sun has shown signs of awakening from it’s year plus long slumber this week. Specifically, a new sunspot group has formed on the Earthward facing side, and is now rotating towards the limb. This is definitely part of the new solar cycle #24, as characterized by its reversed polarity. Thus far, this solar cycle has been off to a sputtering start, at best. All amateur scopes, be they hydrogen Alpha, Calcium K, or safely filtered white light are encouraged to watch as this “monster” sunspot rotates around this Sun’s limb. The group already shows the envelopment of a fine dark umbra embedded in a pale penumbra, and will hopefully throw some looping prominences up through the chromosphere as it rotates from view. If you do not have optical means, you can still follow the action via SpaceWeather (the link above) or the Solar Heliocentric Observatories’ (SOHO) website! Enjoy!

Determine your Longitude: the Lunar Eclipse Method Part II

Hopefully, you had clear skies at your locale. My luck was pretty good… mostly clear skies through-out! My initial impressions were that of a very bright eclipse; the southern rim of the moon seemed especially bright. The color ranged from a dark blood red on the northern edge to an overall brownish glow. This seemed particularly prominent through binocs. And it was extremely cold! Temps ranged around zero Fahrenheit. The night was even punctuated by a fast pass of spy satellite USA 193, on what turned out to be its final orbit. So much for a scoop by Astroguys…

[Read more...]

Determine Your Longitude: the Lunar Eclipse Method Part I

We’re back now with a new look! Hopefully, it’s less of an eyestrain for our loyal legion of readers… and just in time for this months’ Lunar Eclipse!

Getting an accurate fix on your position has long been a bane of the world traveler. Long before Global Positioning Systems, a way was sought for navigators to calculate their location using the stars. Latitude was easy enough; in the Northern Hemisphere, you simply have to measure the angle of Polaris, also known as the North Star, above the horizon. [Read more...]