StarWatch for the greater Lehigh Valley



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[Moon Phases]


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1372    December 4, 2022:   Full Moon To Nearly Graze Mars
We are in for quite a treat this Wednesday, December 7. Observers eastward of a line running from Pittsburgh through State College and Wilkes-Barre, Pennsylvania will get the opportunity of witnessing the planet Mars incredibly close to the limb (boundary) of the moon. For Lehigh Valley residents, the separation will be less than three diameters of the Red Planet or about 40 seconds of arc. Along the boundary line, Mars will graze the mountainous southern limb of the moon. Westward of this position, the moon will occult Mars for a relatively brief period of time. * View the waxing gibbous moon catching up to Mars on Sunday, Monday, and Tuesday and creeping near to Mars after sundown on Wednesday, December 7. Then watch as the moon's closest approach happens just before 11 p.m. (10:52 p.m.) on Wednesday. Use binoculars to enhance your view, or hide most of the full moon with your thumb or a small piece of cardboard to reduce contrast and make the Red Planet easier to see. The picture below is for the Lehigh Valley and tells it all. Enjoy! Ad Astra!

[Moon Grazes Mars]
The moon's southern limb will miss occulting Mars by about 40 seconds of arc in the Lehigh Valley. To give an idea of how close that is, there are 1,296,000 seconds of arc in a circle. Drawing by Gary A. Becker using Stellarium...

1373    December 11, 2022:   Geminids by Moonlight This Week, Not A Bust
The activity of all of the major meteor showers this year, except the January Quadrantids, has been subdued by bright moonlight, and so will the upcoming Geminid Meteor Shower which will reach its maximum action on the night of December 13 and the morning of the 14th. However with the Geminids, you will still be able to witness an enjoyable display because this shower produces the highest meteor rates of the year. As many as 200 shooting stars per hour might be noticed from a moonless, rural locale which could translate into 25-40 meteors per hour from a suburban location bathed in relatively bright moonlight. * How bright will the moon be? When the moon is at its quarter phase, half illuminated by the sun, it is about eight percent the brightness of a full moon. After first quarter or before third quarter, the brightness of the moon increases substantially, illuminating the sky, easily casting shadows on the ground, and drowning out fainter meteors. On the maximum night of the Geminids, December 13th into the 14th, the waning gibbous moon will be twice as bright or about 0.75 magnitude brighter than a third quarter moon. This is still nearly five times less intense than a full moon, not nearly enough to put a kibosh on an enjoyable evening of meteor viewing. The frail waning gibbous moon will rise about 11 p.m. local time and be located in Leo the Lion, 50 degrees to the east from where Geminid meteors will appear to diverge. Make sure that Luna is not in your line of sight while observing. * Geminids will trace back to the star Castor, the second brightest luminary of the Gemini the Twins constellation. See a map below. That is because the meteoroids are basically moving parallel to each other in space while orbiting the sun. The analogy is similar to looking down a long, straight stretch of highway. The sides of the throughfare which are parallel to each other will appear to diverge from a distant vanishing point, which in meteor astronomy is called the radiant. If the shooting star does not trace back to Castor, it is not a Geminid. * Meteors are also more plentiful near dawn because the part of the Earth facing the new day is plowing into the swarm of dross, analogous to why the front windshield of a moving vehicle gets slammed by more raindrops during a downpour than the back window. In the early evening hours before midnight, our location on Earth is similar to a rear window view of the heavens. That begins to change around local midnight. In addition, the Geminids can produce numerous bright meteors, and some spectacular fireballs which moonlight will not hide. * For the best use of your observing time, bundle up and head outside a few hours before dawn when the East Coast is rushing into the meteoroids; outdoor Christmas and house lights are turned off, and the sky is generally at its darkest even with the moon. The radiant will also be high in the sky, allowing observers to witness meteors streaming from all directions, another reason why rates are generally higher in the morning. Good Geminid meteor hunting to all! Stay warm. Ad Astra!

[Geminid Radiant]
Map by Gary A. Becker using Software Bisques's The Sky...

1374    December 18, 2022:   Ursids On The Prowl This Week
Unbearable might be the best way to describe the meteoroid stream that emanates from the body of the constellation of the Little Bear, producing the annual Ursid Meteor Shower. Little is known about this cold weather event which takes place during the busiest and cloudiest time of the year and cannot be seen from the warmer Southern Hemisphere. It is also following the euphoria of the most active annual meteor shower, the Geminids, just slightly over one week before Ursid activity is at its highest. Ursid meteors can be observed from December 17th through the 27th. * This year, the Ursids peak on the morning of December 22. Normally, this amounts to no more than about a half dozen meteors per hour; however, like most meteor events, rates can vary depending upon whether the Earth passes through a thread or threads of denser meteoroid debris. Such a prediction for the Ursids is being made for the predawn hours of December 22. * Meteor showers owe their existence to the dross released from active comets orbiting the sun or comets that have settled into retirement within the asteroid belt. The progenitor of the Ursids, Comet 8P/Tuttle, was discovered by Horace Parnell Tuttle (1837-1923), on January 5, 1858. Tuttle was an American astronomer and Civil War veteran. * Comet 8P/Tuttle is periodic with a 13.6-year orbital cycle that last reached perihelion, its closest position to the sun, on August 27, 2021. Enhanced activity was expected last December but did not materialize; however, higher than average hourly counts were noted in 2006 through 2008 and in 2014 and 2015. Much higher tallies were noted in 2016 through 2018. * This year, two filaments of debris are of interest. One is predicted to intersect the Earth on December 22 at 5:21 a.m., EST. This is extremely favorable for the East Coast because not only will the radiant, the position from which the Ursids will appear to diverge, be higher in the sky, but our location on the Earth will be moving into the cometary debris similar to the front windshield of a car plowing through a rainstorm. Much more rain impacts on the front windshield than on the rear glass. Rates are predicted to increase to 20 meteors per hour during this passage. The second intersection is with a debris field that was released by the comet in 843 AD. For East Coast observers, that happens at 9:22 a.m., fully two hours after sunrise. West Coast onlookers and those in Alaska and Hawaii should benefit with enhanced activity. * If you are going to observe the Ursids, be outside by 4:30 a.m. Meteors will appear to diverge from just above the bowl of the Little Dipper (body of the Little Bear) which will be about 40 degrees above the northern horizon. Polaris, the North Star, is located at the end of the handle of the Little Dipper. Focus your attention above that area, near the zenith where the sky will be at its darkest. Unlike this year's Geminids which were affected by unwanted moonlight just one week earlier, the new moon occurs on December 23, one day after Ursid maximum and will not be a factor in the morning sky. Good Ursid (Bear) hunting to all. Go below for a sky map showing the Ursid radiant. Ad Astra.

[Ursid Meteor Shower Radiant]
Map designed by Gary A. Becker using Software Bisque's The Sky...

1375    December 25, 2022:   Mars' Near Graze Was a Wonderful Holiday Gift
What appeared to be a lump of coal turned out to be a diamond in the rough, but first the coal.

Conditions had been dreary, damp, and rainy for days, and the National Weather Service showed the entire East Coast socked in with clouds and drizzle along the path of a spectacular grazing occultation of the moon and Mars. My friend Pete and I gave up our plans to drive to a nearby location in Pennsylvania or New York where the northern hemisphere of Mars with its white polar cap could be seen partially disappearing behind the southern limb of the moon. I also cancelled the event for about a half dozen of my students who were interested in viewing the near occultation from the Sky Deck atop the Collier Hall of Science at Moravian University. That is how dire conditions looked. Cloud cover was predicted by the NWS to be 95 percent at the time of the graze with areas of dense fog developing later that evening. * To my complete surprise, the infrared radar showed that cloudiness at 8 p.m. on December 7 was minimal with high, thin clouds present over most of the state. Denser, overcast conditions were still prevalent across the Mason-Dixon line and southeastern PA, where the boundary of a cold front was slowly making its way southward. * Since I had no way of accurately polar aligning an equatorial mount, I decided to keep it simple with my DSLR camera and a telephoto lens mounted to a tripod in anticipation of any clear spots that might develop. Pete also stood by his 11-inch Schmidt-Cassegrain ready to image some 30 miles to my south. Gradually, the sky began to cooperate, becoming mackerel in texture with high altocumulus clouds that allowed quick glimpses of the veiled moon and a reddened Mars surrounded by a colorful lunar corona. * I must have taken a hundred images with only a handful that I saved because of the difficulty in anticipating a proper exposure due to the scudding clouds. It became more overcast again with two thin levels moving at almost right angles to each other, one set from the east and the other from the north. I didn't realize it until later, but the southbound clouds were revealing the drier air from the cold front beginning to work its way into the area.

That's when the diamond in the rough vividly appeared next to the encroaching moon.

The ground temperature remained balmy in the 50's, but the sky went through a rapid cleansing and within 15 minutes, thinning puffs of rushing altocumulus were playing hide and seek with the moon, acting as a distinct boundary between clear and mostly cloudy conditions. By the time of closest approach at 10:52 p.m., the clouds had retreated southbound for both Pete and me, and through binoculars, a reddish diamond was nearly in contact with the full moon. * What a glorious sight and a wonderful Christmas gift, I thought. Both Pete and I were able to capture the event in different formats when the moon and Mars were at their closest, less than 40 seconds of arc in angular distance. By midnight, Mars could be discerned visually by placing a finger over the full moon, but that was not the case during the time when the Red Planet was closest to the moon. Binoculars, at a minimum, were necessary. Two hours later, as I finished writing my thoughts for this article, clouds had returned, and the moon and Mars were once again veiled. * For East Coast observers where clouds and precipitation prevent about half of anticipated astronomical events to be seen, this was a nice Christmas treat to an extremely rare astronomical event. Pictures are posted here. Happy Holidays. Ad Astra!

[Moon-Mars Graze Map]
Map courtesy of the Royal Astronomical Society of Canada...

[Moon-Mars Near Graze, Corona]
During the majority of time leading up to the moon's closest separation from Mars, the sky was mostly cloudy. Gradually, the overcast became broken, and through one brief opening the moon and Mars were glimpsed along with a beautiful corona. Coronas are diffraction effects caused by minute water droplets or ice crystals bending the moonlight into a blue interior surrounded by a reddish exterior. Gary A. Becker image...

[Moon-Mars Near Graze]
This spectacular picture was recorded by Peter K. Detterline in Douglassville, PA. It shows a greatly magnified image of Mars when it was closest to the moon taken with an 11-inch, Schmidt-Cassegrain reflector. Peter took several thousand rapid fire images of the event at about 100 frames per second. A computer program then picked out the best 500 frames and these were stacked to lessen the atmospheric turbulence which is the biggest factor in reducing image detail. Great job, Pete. You should be teaching astrophotography at Moravian University. Peter K. Detterline image...

[Moon-Mars Near Graze]
This is a more tradition view of the event as seen through binoculars or a small telescope. All of my images were recorded with a tripoded Canon 80D, DSLR camera and a 70-200mm Canon telephoto lens coupled to a 2X extender for an effective focal length of 640mm (12.8 power). Images of Mars were shot at F/14, ASA 800 for 1/100th second. Images of the moon were taken at 1/800th second. The two images were then combined. Gary A. Becker photography...

[Moon-Mars Near Graze, Compilation]
These six photos show the progression of the December 7 near graze of the moon and Mars. The closest angular distance of the moon to Mars occurred at 10:52 p.m. EST (far left bottom image). Gary A. Becker photography...

[December Star Map]

[December Moon Phase Calendar]