StarWatch: Moravian College Astronomy

DECEMBER 2019

DECEMBER STAR MAP | MOON PHASE CALENDAR | STARWATCH INDEX | NIGHT SKY NOTEBOOK

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lunar phases

1215 DECEMBER 1, 2019: Moonlit Geminids Next Week: If you had the opportunity of catching the spectacular conjunction of Venus and the thin crescent moon last week, you know that the moon is waxing, becoming brighter. Until it reaches first quarter, half on—half off, light to the right, it really doesn’t present too much of an observational hassle. A first and last quarter moon is about 1/10th as bright as a full moon. After first quarter, however, the brightness of the moon burgeons, illuminating the sky and easily casting shadows on the ground if you are away from any direct streetlights. I remember losing my intervalometer on a Bryce Canyon trail in 2006 while photographing the park after dark, one of my jobs as a Night Sky Interpreter. The device was expensive and necessary for the type of photography that I was performing. My wife was along on that hike and I left her, albeit a little nervous, on the canyon rim while I descended back down the trail, headlamp blazing. After a few awkward steps, I stopped and turned off my light which was causing all shadow detail to disappear and the trail to look flat and featureless. The moon was almost full that evening, a fat, waxing gibbous, a beacon of bright reflected sunlight illuminating the landscape, vivid enough for me to perceive the reddened rock of the canyon. Within a minute my eyes adjusted from the uber-light of my headlamp to the natural light of the nearly full moon with plenty of detail along the trail to navigate. I found my intervalometer about a half mile down the trail, 50 yards from where my last tripoded image had been taken. There was no mistaking it. After returning, Sue and I walked to a rim overlook where I captured the lightning of a distant thunderstorm playing against the surreal, moonlit landscape that makes Bryce Canyon such a national treasure. I have included that image with this article at www.astronomy.org/StarWatch/December/index-12-19.html#12-1-19. The same intensity of moonlight that makes Bryce by night so stunning, blankets most meteors from view. In fact, the bright, waning gibbous moon will be in Gemini on the night of maximum, December 13/14, only about 12 degrees away from the star Castor, where the Geminids will appear to be radiating. That is the big negative about this year’s Geminids, but there are also positives. Because the Geminids are active between December 6-19, the nights bracketing December 13/14 should also prove fruitful. Look away from the moon, but because Luna is close to the radiant, the location from where the meteors will be diverging, Geminids will trace back to the moon. Shooting stars are also more plentiful near dawn because that part of the Earth is plowing into the swarm of dross which creates the meteor shower, analogous to why the front windshield of a moving vehicle gets slammed by more raindrops during a downpour than the back window. In addition, the Geminids produce numerous bright meteors and occasionally a fireball which moonlight will not hide. Just make sure that the moon is not in your field of view. Expect to see rates of 10 to 15 Geminid meteors per hour after midnight. By dawn, the bright moon will have moved into the northwestern sky, and you will have a much greater swath of the heavens to view where direct observation of Luna can be avoided. Stay warm, and enjoy the moonlit Geminids.

1216

DECEMBER 8, 2019: Binoculars Under the Tree

I truly don’t understand what it is about the Christmas season that makes parents contemplate purchasing a telescope, but it is always a topic of discussion that arises most often at this time of the year. People go to a Walmart, pluck down $130 or so, and give their kids an absolute piece of mechanical and optical junk which will do more to turn them off to the wonders of the heavens than to inspire them. Think of a base price for a decent telescope as starting around $500. That would include an inexpensive eyepiece or two, but the system would meet the criteria for producing an astronomically acceptable image. If you are willing to spend that type of money, I would strongly suggest visiting in person Skies Unlimited in Pottstown, PA at 46 Glocker Way, 19465/610-327-3500, https://www.skiesunlimited.com/. Bob, Ted, or Dave are extremely knowledgeable about the products that Skies Unlimited markets and are willing to spend the time working with you to choose the instrument that won’t be a disappointment. If you read StarWatch from afar, my advice would be to visit Orion Telescopes at www.telescope.com. Both stores offer scopes for under $200, but I would strongly suggest avoiding the temptation. Another negative aspect of giving a telescope at Christmas is that it is cold outside. See how long you last in a 10 mile an hour breeze on a night where the temperature has dipped to 25 degrees F. Also, most people make the mistake of setting up their new scope for the first time in the dark. There is a lot that can go wrong with that game plan because telescopes are relatively complicated pieces of equipment, and they all have their little quirks, even the high-end ones. You should first practice getting it right in a well-lit environment. Drop a screw in the snow while setting up, and well, literally you are screwed. Just in case you think that you’ll be using your new scope for the first time on Christmas night, the winter months, particularly December, are also the cloudiest times for the mid-Atlantic and Northeastern states. It sounds like I’m a downer on telescopes, but that is not the case at all. I’m interested in an honest introduction of kids and adults to a hobby that inspires and educates, and asks some of the fundamental questions about our human existence. How did the universe begin? Where are we going? Where are we now, and how will it all end? Buying a telescope first is similar to walking before learning to crawl. There is a natural evolution to human development. Curiosity leads to more in-depth investigation, and binoculars are an excellent way to begin igniting that desire to explore the cosmos. Binoculars are ready to go right from the box, are easily used, and provide immediate positive reinforcement. They are also portable and are generally more rugged than telescopes. All in all, binoculars offer a great way to begin your explorations of the heavens, and then if the interest burgeons, graduate to a telescope. More about these little gems next week. Both Skies Unlimited and Orion Telescopes also offer a wide variety of binoculars for sale.

1217 DECEMBER 15, 2019: Why Binoculars for Christmas?: Several weeks ago, Greg Derr-Haverlach, one of my astronomy students at Moravian College brought in a pair of binoculars that he had just purchased and asked me for an evaluation. Although not overly impressed, I was able to obtain a good central focus, and the optical alignment of the two components was fine. Greg and I had been talking about telescopes versus binoculars for several weeks after class, but he did not seem phased by my neutral assessment, so I asked him the big question, “How much did you pay for them?” “Got them at a yard sale,” Greg responded, “four bucks.” “Nice going” was my remark. The guy who you bought them from was truly robbed.” I would have certainly purchased that pair for Moravian’s optical arsenal had I fallen upon that yard sale first. So how much does a decent pair of new binoculars cost today? Figure about the same amount of money that you would remit for a really crappy telescope at Walmart, about $100-$130. Consider that any optical equipment purchased for someone else should have a return policy from the manufacturer or store from which they are bought because optics are very personal. As an example, when I looked through Greg’s binoculars, I could not see the entire field of view. That’s because I wear glasses and the eyepiece end of the binoculars was farther away from my eyes. Greg doesn’t wear glasses, and therefore, he could bring the binoculars right up to his eye and see everything. That is called eye relief, and it there is no compromising here because a field of view that has poor eye relief produces a very uncomfortable image for the user. Binoculars that have at least 20mm of eye relief are appropriate for eyeglass wearers and, of course, these binoculars cost a little more on average; but I am getting a little ahead of myself here. Binoculars usually have two numbers associated with them, such as 7x50 (7 by 50). The first number tells you the magnification the binoculars will produce while the second number tells the buyer the diameter of the light gathering lens in front. Keep the magnification at 10 power or less because the higher the magnification the more difficult it will be to keep the binoculars steady. Dividing the first number into the second number gives the observer the diameter of the exit pupil in millimeters, an important consideration especially if you live in a rural locale and your eyes are young. An eye-healthy child up to the age of a young adult who does not smoke should be able to have their pupils expand to 7mm when fully dark adapted, just what the exit pupil is for 7x50 binoculars. The 7mm exit pupil was at one time the standard for binoculars that were dedicated to astronomy; however, since most of us live in light polluted locales, the pupils of our eyes can never reach this maximum diameter, so this consideration has become less important with respect to why or why not binoculars should be purchased. Seven by 35, 8x42, and 10x50 binoculars are certainly fine choices for astronomy, but any binocular will allow the viewer to see more than the unaided eye and deeper into space. Consider purchasing a small star atlas that clearly shows a modern rendition of the constellations, names the more luminous stars, and indicates some of the brighter clusters and nebulae and other objects that can be seen with binoculars. Other considerations might be whether the binoculars are widefield or produce a standard field of view, if they are water resistant or waterproof, and particularly if being purchased for a younger child, how shock resistant they might be if they are dropped. Finally, consider that binoculars can be used during the day as well as at night because they produce images that are right side up. Indeed, binoculars provide one the best and least expensive ways that you can introduce someone to the wonders of nature, both in the heavens and across the varied landscapes of the Earth.

1218 DECEMBER 22, 2019: Under the Same Canopy: John Denver, in his Harbor Lights Concert, tells a story of a vivid dream he had about his wife, Annie, on the occasion of their 14th wedding anniversary back in 1985. He was in Shanghai, she in Colorado. It was morning in China, the evening of the previous day in Colorado, and Annie had just returned from a hike with friends; but the two connected and spoke. In the conversation Annie brought up the subject of the rising moon which she had seen and wondered if it was the same one that her husband would be viewing in China. Denver responded to his Boston audience, “Probably (long pause with audience laughter), I don’t know… So that was a really very wonderful thought; I shouldn’t make light of it here.” Denver pondered Annie’s feelings all through that day. No matter where he went, no matter what he did, no matter what he saw, the day was a complete blur, except for a song that was germinating in his mind. It would be called Shanghai Breezes, and you can listen to it here, https://www.youtube.com/watch?v=sxaE4dcnZo0. The heavens as a unifying theme for all humankind is certainly not original, but it is a very beautiful concept, which lends comfort to me when times are turbulent. However, it is not just the same moon, the same sun, and the same stars that we all witness; the heavens have not changed since the beginning of civilization 6000 years ago, and look pretty much as they did when Europeans created the first cave drawings to celebrate a successful hunt 35,000 years in the past. That luminary shining brightly after sundown in the southwest is really the planet Venus and for me, a wonderful symbol of this Christmas season. Venus which has been a stable member of Earth’s sky scenery since the birth of our solar system 4.5 billion years ago can be observed presently throughout most of the northern hemisphere and all of the southern hemisphere where darkness falls. My friend, Peter, traveling in Australia while this article is being written, is observing Venus in the southwest just like I am, a nice reminder of the connectivity of four decades of friendship that can still be tangibly maintained half a world away. Even more remarkable is the air that we breathe. The oxygen and nitrogen contained in each breath can be reprocessed over time into other molecules, but the one percent of the atmosphere composed of argon is inert and unchanging. There are no compounds of argon, and it is too heavy (massive) an atom to diffuse back into space. So with every breath we take, we inhale the collective souls of all humanity, something like 50 billion people who have lived and are living on “this pale blue dot.” John Denver concludes in his introduction to Shanghai Breezes “that we should always remember, all of us, no matter what language we speak, no matter what color we are, no matter the form of our politics or the expression of our faith. We all live under the same moon and the same stars; we’re not so very far apart—And the moon and the stars are the same ones you see; the same old sun up in the sky; and your love in my life is like heaven to me, like the breezes here in old Shanghai.” Peace!

1219 DECEMBER 29, 2019: Perfect Conditions for the Quadrantids: As meteor showers go, the second half of the year is stacked with the big shows: the August Perseids, the October Orionids, the November Leonids, and the king of them all, the December Geminids. When bright moonlight interferes with one of these events, it usually means that all four will succumb to similar fates, and that was the situation in 2019. After the Geminids the Earth intersects the debris of only a few comets, and shooting star rates dip to their lowest nightly tallies until April. The one exception is the Quadrantid Meteor Shower which occurs in 2020 on the morning of January 4 and will peak for East Coast observers around 3 a.m. EST, about as perfect as it gets. Moonset that evening will be just after 1 a.m. What makes the Quadrantids so elusive is that they have a very narrow period of maximum activity—about six hours; therefore, if you are not positioned in the correct region of the Earth when it slices through the narrow bands of dross from comet turned asteroid 2003EH1, chances are that you will see very little or nothing at all. That was the case when I observed the Quads in the mid-70s with several Dieruff students who were brave enough to weather a very transparent, but cold January evening where the windchill must have dipped into the low teens. The ground had a light covering of fluffy snow, and the sky was scudded occasionally with fast moving cumulous clouds. Blowing snow accompanied the bone-numbing gusts of wind that added to our collective misery. I just remember being cold from the moment I crawled into my sleeping bag to the time when our group “bagged” it, a little after 11 p.m. I also remember one of my students, Steve Pfenninger, who forgot his gloves and spent most of the evening huddled inside of his car trying to keep warm. We were probably observing for under three hours, and our collective count was around a dozen meteors, mainly because our part of the Earth was not in the best position to pass through the narrow strands of debris from 2003EH1. The 2003 indicates the year in which the comet associated with the Quads was discovered; so before that time the progenitor of the Quadrantids was not known, and the ability of astronomers to predict the period and location of highest activity was virtually nonexistent. All we knew was that sometime between January 2-4 under moonless, rural conditions, an observer somewhere on the Earth might see over 100 meteors per hour. Knowing the comet’s orbit precisely has allowed astronomers to associate this object with Quadrantid meteors and to predict the target region of highest activity with much better precision. Observe the sky in its darkest area, the zenith, but point yourself towards the NE, the location of the radiant from which the Quadrantids will appear to diverge. Quadrantes—Quadrans Muralis, the Mural Quadrant, a device which predates the telescope, measured the altitude of objects when they were due south. The star pattern was never accepted by the International Astronomical Union when they parceled the sky into 88 constellations in 1928. When the meteor shower was discovered in 1835, Quadrantes was noted on some star charts, hence the name of the shower that emanates from a star pattern no longer in existence was created, a unique remnant of bygone days. Clear skies for the New Year and the Quads!