May 28, 2017

AstroEvent: A Loooong Central Eclipse!

Last December’s colorful lunar eclipse… (Photo by Author).

One of nature’s finest spectacles is on tap this week for observers stationed from Europe to the Far East. A total lunar eclipse of a particularly long duration is in the offing spanning the night of June 15th-16th. The duration of totality is 100 minutes, nearly the maximum 107 minutes possible. A question we frequently receive as of late is “how often does such a long eclipse occur?” Well, keep in mind that the umbra or the dark inner core of the Earth’s shadow is about 3 times the apparent diameter of the Moon as seen from Earth. For an eclipse to occur, the Moon has to be very near the ascending or descending node of the ecliptic; its orbit is canted about 5 degrees to our own and thus usually passes to either side of our 1.5 degree wide shadow. For an ideal eclipse to occur, the Moon would have to occupy that node while its smack dab in the center of the Earth’s shadow… this current eclipse will be the longest in duration until July 27th, 2018 with a duration of 103 minutes. In fact, a quick perusal of NASA’s eclipse website reveals that although this week’s eclipse is the longest this century thus far, & eclipses on 2029, 2047, and 2094 also beat it out for duration, making it the fifth longest of the century.  This could as prove to be an especially dark eclipse, as the Moon passes through the central part of the Earth’s shadow… be sure to note the Danjon number of the eclipse, as well as use our tried and true method of magnitude estimation via the reverse binocular method. Particulars of the eclipse are as follows;

Penumbral 1st contact: 17:25 UT

Umbral 1st contact: 18:23 UT

Totality Begins: 19:23 UT

Totality Ends: 21:03 UT

Umbral last contact: 22:02 UT

Penumbral last contact: 23:01 UT

The penumbral phases will only appear as a diffuse shading, while entry into the umbra will be more distinct. Also, there has been plenty of volcanic activity worldwide in hot spots such as Chile and Iceland, so the eclipse may prove to be quite colorful. And yes, this eclipse occurs in the constellation Ophiuchus, the bad boy “13th constellation” of the zodiac! (Shhh… don’t tell astrologers!) This is also the 68th eclipse of saros 118.

Photographing the eclipse with even a moderate (i.e. 200mm or larger) zoom is relatively easy; just remember that the Moon will be much darker during totality than partial phases and thus you’ll need longer exposure settings… I’ve even lost telescopic acquisition of the Moon during particularly dark eclipses!  Finally, some interesting occultations of background stars will occur during totality, the brightest of which is the +4.8 magnitude star 51 Ophiuchi as seen from the Far East… speaking of which, folks around the periphery of the eclipse (i.e. Japan, U.K. and Australia) should be vigilant for the possibility of a Selenelion, or the chance to catch totality while the Sun is still above the horizon!

Well, it looks like us folks in North America will just have to sit this one out, or at least watch it through broadcast via the Net… will tweet links (@Astroguyz) if live… We’ll just have to console ourselves with a rising pre-eclipse Honey (or do you say Strawberry or Rose) Full Moon as we eagerly await the next Total Lunar Eclipse of December 21st that occurs for North American observers at moonset/sunrise!

The Astro-word for this week is Lunation. This is simply the period of time that it takes the Moon to return to the same phase (i.e., New to New, Full to Full, etc). This is the same as our friend, the synodic month, and is on average 29 days, 12 hours, 44 minutes and 3 seconds long. This period can however, vary by up to 15 hours due to the elliptical nature of the Moon’s orbit about the Earth the period for which is getting ever so slightly longer as the Moon recedes from us by about 38mm per year. This means that eventually, total solar eclipses will no longer occur as the Moon of millions of years in the future will be visually tinier than the Sun, even at perigee. We will, however continue to enjoy total lunar eclipses during that far off epoch!

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!