Moon and Mercury Amaze in May

Casual stargazers and avid amateur astronomers are anxiouslyawaiting a couple of astronomical treats during May. Though theupcoming transit of Mercury across the disk of the sun will bereserved for experienced astronomers, the total lunar eclipse canbe observed by everyone. So with good thoughts in mind for atranquil and mild month of May with clear skies ahead, let's seehow we can maximize our viewing of the astronomical opportunitiesawaiting us.

First up on May 7 at sunrise is a fairly rare event (only 13 or14 times per century) that should only be observed by experiencedamateur astronomers. The event, a transit of Mercury, occurs whenthe planet passes between the Earth and the Sun. As one mightexpect, no one should look directly at the Sun at any time. Infact, the image of Mercury silhouetted against the solar disk is sotiny that it couldn't be seen with the naked-eye anyway.

To observe this transit an observer must use the safe solarobserving filters and or techniques one commonly uses for solarobserving. If you are not experienced with safe solar observingtechniques, do not attempt to view this transit.

As I have always stated when reporting about partial solareclipses in our area, any time you observe the sun you must observecaution as well. You don't want to risk serious eye damage. Again,if you don't have solar observing experience, you might want to geton-line and surf the web for a site that may show the transit inreal-time. It may not be quite the same experience as observing itfirsthand, but it will indeed be safe.

For those of you who know what you're doing, this transit willbe a little challenging, since the transit is already in progressas the sun rises here in the northeast. In fact, by the time ofsunrise for us, around 5:30 am EDT on the 7th, we will have missedabout four hours of the event already. Unfortunately, you'll needto wait a little while for the sun to rise higher into the sky.Don't forget, you'll need a great observing location with anunobstructed horizon to be successful. Thin clouds won't spoil theview too much, but thick clouds will.

Mercury will look like a tiny, perfectly round and very blacksunspot, close to the edge of the solar disk. It can be furtheridentified by how fast it will move. Sunspots don't moveappreciably in a small amount of time.

Remember, you'll only have about an hour to observe this rareevent before it ends. Pay close attention as Mercury begins to moveoff the solar disk around 6:30 am. A phenomenon known as the blackdrop effect takes place. As Mercury is just about to exit the diskat around 6:34 am, the dark circular image elongates and appearslike a teardrop, looking like it's being drawn out. Use a low-tomedium-power eyepiece to start, then use whatever magnificationprovides the most aesthetic image for you.

One more point, if you have the capability, you might want toattempt to image this rare event. Film or digital, it's yourchoice. If you get a good image, by all means email us a copy atwww.theskyscrapers.org It may end up in our gallery of images.

The next major astronomical event in May occurs on the night ofthe 15th-16th. While Mercury became visible during its transit of thesun, our nearest neighbor in space may indeed disappear from view.It won't happen in the blink of an eye, rather it will be more likea magician s cape being slowly drawn across the lunar surface. I'mtalking about the Full Moon sliding through the Earth's shadowproviding a total lunar eclipse.

We are fortunate to be situated here in New England, for wewill be able to follow the progress of this event from start tofinish. The caveat to that I hate to say, weather permitting ofcourse!!

A total eclipse of the Moon occurs when the Sun, Earth and Moonare nearly in a straight line. With the Earth in the middle of thiscelestial configuration, our planet's shadow will sweep across thelunar surface. It's like compressing an entire month's phase cycleinto one evening.

The eclipse begins at 9:05 pm on the 15th and ends at 2:15 amon the 16th for a duration of 5 hours and 10 minutes. You don'tnecessarily have to watch the entire eclipse to be impressed withthe beauty of this event. Don't have much free time? Just watchthrough the end of totality. After that it's anti-climatic anyway.To help you plan your evening, the accompanying graphic will showyou at a glance what time the significant events will take place(as noted A-G). All times are Eastern Daylight Time (EDT).

The Moon enters the Earth's faint shadow called the penumbraat 9:05 pm and the eclipse begins (A). The penumbra is so dim thatthe Moon's "first contact" with it cannot be seen. Only as the Moonslides deeper into the shadow will a keen-eyed observer see asubtle shading of the lunar surface. Just prior to the Moonentering the Earth's dark umbral shadow one should notice that themoonlight looks somewhat subdued.

At 10:03 pm the Moon encounters the dark umbral shadow of theEarth (B). The Moon will be moving eastward in our sky when itencounters the Earth's shadow. Therefore, watch for the shadow tosweep across the lunar surface from left to right. By the time theMoon is more than halfway through the umbra we should be able totell if this is going to be a dark eclipse or a bright one.

Sometimes the Moon will completely disappear from naked-eyeview (dark eclipse) due to large amounts of dust spewed into theEarth's atmosphere by recent volcanic activity. The total lunareclipses of 1992 and 1993 were dark eclipses because of MountPinatubo's eruption. Then we have the type of eclipses where theMoon is a coppery color, with various hues of orange and yellow(bright eclipse). The total lunar eclipses of April and September,1996, were bright eclipses.

With no major volcanoes currently erupting, I would predict theupcoming total lunar eclipse to be a bright one. It should remainvisible even during mid-totality, presenting a collage of yellowand orange hues to the observer. The umbral shadow completelyenvelopes the Moon at 11:14 pm. That's the moment when totalitybegins.

Totality will last for only 52 minutes, during which time youcan scan the Moon's surface for a variety of colorful hues. Thatis, of course, if it doesn't disappear from view. Even during thedarkest eclipses that I've observed, a telescope will still revealsome rusty browns or reds on our lunar neighbor. Mid-totalityoccurs at 11:40 pm (D). Twenty-six minutes later a sliver ofbrightness marks the end of totality at 12:06 am (E) as the Earthand Moon move out of alignment and sunlight once again strikes thelunar surface.

The partial phase will last until 1:17 am (F). At that time thedark umbral shadow will leave the Moon's surface. Soon thereafter,like the beginning of the eclipse, the remaining phase will hardlybe noticeable at all as the Moon begins to return to fullbrightness. For just under another hour, until 2:15 am when theeclipse ends, the Moon will remain within the lighter penumbralshadow (G). Only while the Moon is still deep within the penumbralshadow will the lunar surface appear in subdued light.Most importantly, if you have binoculars or a telescope, thisis the time to put them to good use. The more optical aid anobserver uses, the more detail one will discern. However, don'tdespair if you don't have access to expensive equipment. MotherNature provided you with a pair of the most valuable observingtools - your eyes! Use them to follow the progress of thisbeautiful event.

Enjoy the celestial show performed by the Sun, Earth and Moonon May 15-16. Make every effort to observe this beautifulphenomenon. If you miss it this time around, we've got anotheropportunity in November when the next total lunar eclipse willoccur here in New England.

Good luck and keep your eyes to the skies!