July 27, 2017

Review: Christmas Ghosts edited by Kristine Grayson

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A strange dichotomy exists between Halloween and Christmas.  Not only to the two holidays have their roots in pre-Christian celebrations— Hallows Eve marks an approaching cross quarter day, and Christmas stakes out the Winter Solstice —but both seem to strike a primal chord of fear and hope.

And as stories such as Tim Burton’s The Nightmare Before Christmas and Charles Dickens A Christmas Carol remind us, the two holidays go hand in hand. And hey, Halloween is the closest thing to a traditional holiday that speculative fiction has, right? [Read more...]

Astro-Event(s): A Solstice, a Meteor Shower and a Bizarre Transit.

The Winter Solstice… here comes the Sun!

(Credit: Art Explosion).

T’was the night before Christmas, and no doubt dreams of high tech astro-gear is dancing thru the head of many a star stricken astronomer out there. But while you’re awaiting those astro-gifts, the universe marches on. [Read more...]

The Solstice Eclipse: An Update

AWESOME!!! (All images and video by Author).

This is just a brief update: the solstice lunar eclipse was one for the record books, a bright Danjon “L4″ and easily visible thoughout totality. A coppery red, this was one of the brightest on record for this seasoned observer… expect a more through after action report in this space later today… more pics can also be seen here at our shinny new Flickr account. Now… sleep!

…a brief nap and the astronomer’s friend, coffee, has brought with it some more processed results, including the stop motion/live footage above and the processed stills below. For those interested, I shot with a JVC Digicam afocally through the 8″SCT, while shooting stills with a piggybacked 800-1600 DSLR. The rig worked out pretty good, all in all; having WWV radio call out time signals in the background was a huge help, as I just let the video run while shooting stills at the top of each minute.

Also, our Twitter “danjon count” was a huge success, with a clean sweep for a Danjon number of L4, the brightest eclipse possible… the power of crowd sourcing in action!

AstroEvent: A Solstice Eclipse!

  

Luna entering the Earth’s shadow during the Total Eclipse of May 15th, 2003 (Photo by Author).

   One of the final astronomical events of the year for 2010 is also one of the biggest. On the night of December 20th-21st, the Moon will undergo a total lunar eclipse. This eclipse will be visible in its entirety for North American observers and at sunrise for European South American observers and sunset for observers in Australia and the Far East. First Umbral contact will begin at 06:32 UTC, and totality will last 73 minutes from 7:40 to 8:53 UTC with greatest eclipse at 8:18 UTC. [Read more...]

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: Happy Winter Solstice!

Time again to reset those sundials... (Photo by Author).

Time again to reset those sundials... (Photo by Author).

Brace yourselves; the Winter Solstice is upon us this week. This is the point at which the Sun reaches its lowest southerly declination and begins its long march northward. This makes for shortened days and long nights in the northern hemisphere and the reverse in the southern. Of course, its not the Sun that’s moving, but the Earth with its 23 degree 26′ minute tilt that causes this variation. Several cultures mark this celestial turn of events, not the least of which is modern day Christmas, which is fixed on December 25th, the solstice date on the old Roman Calendar. Modern reform by Pope Gregory gave us an offset solstice that falls on or around the 21st each year, and will eventually move by one day every 3,000 years. The solstice is always a good time to check out any local chance alignments at sun rise or sunset, as well as note the length of shadows cast at local noon. The precise timing of the winter solstice this year is Monday, December 21st at 5:47 PM Universal Time. Merry Saturnalia/Christmas!

This week’s astro-term is the Chandler Wobble. This is one of the many complex movements of our planet that causes the complex motions of the Earth’s axis to shift slowly. But unlike larger effects such as our friend, the precession of the equinoxes, the Chandler Wobble is much more subtle. First discovered by Seth Carlo Chandler in 1891, this movement amounts to 0.7 arc seconds or about 15 meters of axial shift over a period of about 433 days. This wobble is caused by the “sloshing” motion of Earth’s fluid core and even the drag created by the friction of our oceans. Think of the Earth as a sort of egg with a liquid center dragging us about  as we orbit about the Sun. This amount can vary (it was greatest in 1910) and is enough that modern off the shelf GPS devices can measure it and must take it into account. It can also cause the poles, equator and lines of longitude and latitude to change perceptibly. Along with the drag created by our Moon and Sun, the Chandler Wobble is also responsible for variations in Delta T, causing an occasional tweaking of our clocks by the addition or subtraction of an occasional second!