StarWatch: Moravian College Astronomy

StarWatch for the greater Lehigh Valley

APRIL 2002

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293 APRIL 7, 2002: Ikeya-Zhang Switches to the Morning Sky: Over the past week Comet Ikeya-Zhang sank lower into the northwest at dusk and for me, looking into the city lights, it became somewhat difficult to detect. I-Z appeared, however, to maintain a steady brightness as it increased in size. Earth is still approaching the comet. Views of I-Z were much easier if you were located north of the Valley with a good northwestern horizon like Matt Gustantino of Orefield. He easily spotted it with binoculars from the deck of his home last Thursday. From the Four Corners area, at the Chaco Observatory, 100 miles NW of Albuquerque, NM, John Sefick reported that the comet was an easy naked eye target that showed a small tail with averted vision. So location and a dark sky make all the difference. You can see one of John's spectacular images, as well as other Valley photographs of the comet by going to web StarWatch. Also posted is a locator map for the comet. Feel free to download the map and pictures for your personal use. Over this last week, Ikeya-Zhang became north circumpolar, meaning that it is visible all night. During most of this time, the comet is low in the north, only a handful of degrees above the horizon, but since Ikeya-Zhang is marching northward and away from the sun, each morning finds the comet better positioned for viewing. By 5:00 a.m. Monday the comet is 16 degrees above the northeastern horizon. That's nearly two fists (thumb on top) held at arm's length and stacked one on top of each other. By Saturday at 5 a.m. that distance has increased to 28 degrees or three fists. By April 20, I-Z is nearly 45 degrees or halfway up in the sky by 4:45 a.m. Use binoculars for your observations, and keep in mind that I-Z will not be around forever. It's bound to fade eventually.
IKEYA-ZHANG REIGNS: These three photographs illustrate that Ikeya-Zhang is no ordinary comet. Fran Kittek of Coopersburg, PA used Fuji Press film 800 in his 30-second color exposure of I-Z taken on March 16th (top left). John Sefick of Albuquerque, NM used a 300mm, F/4 Canon lens along with an SBIG-8e CCD camera for his two-minute image of I-Z recorded on March 20th from Chaco Culture National Historical Park near Nageezi, NM (middle). Using a Nikon Coolpix 950 digital camera and an image intensifier, Glen Hacker, of Reading, PA literally snapped this half-second April Fools Day photo of Ikeya-Zhang north of Leesport, PA. The photograph appeared in the Reading (PA) Eagle on April 9th. The camera and intensifier were attached to a 3-inch, F/4 Air Force aerial lens.: Thursday, March 28: Under a full moon and hazy conditions, Ikeya-Zhang's brightness was estimated at +3.6 using Mu Andromedae (+3.86) and Alpha Trianguli (+3.42). The tail length was 2.5 degrees using averted vision and 7x42B Trinovid binoculars. Conditions: hazy, T=50 deg. F., limiting magnitude +3.5.
: Monday, April 1: Tonight provided a good view of Ikeya-Zhang in a clear sky without a moon. I-Z's brightness was estimated at +3.6 using +3.86 Mu Andromedae and +3.69 Zeta Cassiopeia as guides. I-Z's coma appeared larger. Its tail was estimated at 5 degrees using averted vision and 7x42B Trinovid binoculars. Conditions: clear, T=45 deg. F., limiting magnitude +4.5.
: Wednesday, April 3: A cold front pushed through this afternoon and it seemed for a while that the sky would clear. At 7:45 p.m. thin clouds and haze hung in the direction of the comet allowing Ikeya-Zhang to be seen along with its tail, but not well enough for any accurate measurement to be make. I don't believe, however, the comet had lost any brightness from Monday. Condition: mostly clear, T=37 deg. F., wind 10 mph, gusting to 15 mph, limiting magnitude +4.5.
: Thursday, April 4: Despite it being a beautiful cool spring day, the comet is now so low that it seems to be always in the haze near the horizon and the muck of the Allentown's sky glow. At first, I thought Ikeya-Zhang had faded, but when I compared it to +3.89 Mu Andromedae and +4.53 Nu Andromedae, it was consistent with the night before, about +3.5. The tail was much shorter because of the haze, about two degrees. About one half dozen degrees above the comet, the sky appeared much clearer. Conditions: clear, calm, T=37 deg., limiting magnitude +4.
: Friday/Saturday, April 5/6: The comet's brightness appears to be holding steady at about +3.5 magnitude in comparison to other stars in the vicinity. Its tail was at least 2 degrees despite looking into Allentown's sky glow. Ikeya-Zhang was only about seven degrees above the horizon. Conditions: clear, T=low 30s, for both evenings, slight breeze, limiting magnitude +4. Because of trees, I'll have to wait until about Wednesday before I can catch the comet in the morning sky from my property.
: Sunday, April 7: I could not wait until mid-week and got up at 5:00 a.m. EDT to find Ikeya-Zhang a barely naked eye object from Coopersburg. Binoculars were used to find it first. Through my 7x42B Trinovids the comet's magnitude was estimated at +3.4 using +3.69 magnitude Zeta Cassiopeiae as a reference and defocusing the field. Its tail was an easy five degrees and broader than my last good observation of one week ago. Conditions: clear, calm, T=18 deg F., limiting magnitude +4.5.
: Thursday, April 11: At 5:00 a.m. Ikeya-Zhang was easily seen through binoculars for the first time from my backyard. Because of its higher altitude, now 23 degrees, I-Z was positioned against a much darker sky and was repeatedly seen with the unaided eye. I even got the impression that there was a small naked eye tail. Through 7x42B Leitz Trinovid binoculars, the tail was estimated at just over two degrees, a little bit of a disappointment. Even though the comet was more easily seen because of its higher altitude, I felt that in comparison with +3.69 Zeta Cassiopeiae, about six degrees away, the comet was just a tad bit fainter. Both I-Z and Zeta Cas. Could be seen in the same defocused binocular field. I estimated I-Z's magnitude at +3.8. Unfortunately I failed to compare it with +3.8 Lambda Andromedae to the other side of the comet-dah! Conditions: clear, calm, T=35 deg F., limiting magnitude +4.5.

294 APRIL 14, 2002: Do the Walk--Talk the Talk: If you are a weekly reader of this column and you have not taken the opportunity to catch an eyeful of Comet Ikeya-Zhang, then maybe it's time for you to "do the walk so that you can talk the talk." Few individuals have checked out this little gem of a "hairy star," that admittedly has been playing hide-and-seek with us for over a month. It's difficult forcing yourself up at 4:30 a.m., finding your gear, and stumbling outside to make an observation. Just ask any of my first period classes at Allen or Dieruff. Astronomy is not for the faint-hearted. It requires willpower for your brain to punch in the new numbers on the alarm and sheer courage to pull the button that will make it happen. After all, this isn't the first day of fishing season or the start of that big vacation. You're going to get your feet wet, bump into a few things, mutter a few words, and set off a dog or two along the way. But it is for a good cause because the universe invites you to participate in the majesty of its dance. And for perhaps one more week, maybe two, Comet Ikeya-Zhang will be a most willing partner in the northeast. It will delight those who have chosen to rise just a little earlier than most. Last week as I-Z climbed ever higher into a darker predawn sky, I was able to observe it unaided from my suburban backyard. It even had a small smudge of a tail. Binoculars are still highly recommended to bring out Ikeya-Zhang's wispy gossamer appearance and nicely defined head. Through your binoculars, look away from the comet to accentuate its ion tail with your averted vision. If you move the binoculars away from your eyes, you will probably see I-Z on your own. Consult the map at web StarWatch to locate I-Z through late April. Now go out and chase some comet tail!
COMET IKEYA-ZHANG IN THE MORNING SKY: The locations of Comet Ikeya-Zhang are posted for April in the morning sky. Note the time of the observation, because we switch from Eastern Standard Time to Eastern Daylight Time on Sunday morning April 7th. By mid-April Ikeya Zhang will become visible all night, but spend most its time low in the north. Graphics by Gary A. Becker using TheSky software...: Tuesday, April 16: It is now easy to see that Ikeya-Zhang has faded rather dramatically. The tail length was estimated at one degree and brightness at +4.5, using 4 (+4.55), 9 (+4.63), and Alpha Lacertae (+3.76) as comparison stars and defocusing the binocular image. The time was 4:45 a.m. Conditions: partly cloudy (distant lightning), humid, calm, T=56 deg. F. Limiting magnitude +4.0.

295 APRIL 21, 2002: Look to the West: Hide and seek Comet Ikeya-Zhang has shed most of its gossamer tail over the past week and has turned into more of a fluff ball as it recedes from the Earth as well as the sun. By dawn I-Z is placed high in the northeastern sky, but it has become too dim for easy location unless you've been following it. Turn around and set your sights towards the west and the spectacular planetary conjunction which will be unfolding during the next several weeks. A conjunction is merely a gathering of two or more objects in the sky. In this case, the five classical planets seen by the ancients, Mercury, Venus, Mars, Jupiter, and Saturn, will all be visible in the evening western sky at the same time. Some astronomers may refer to this as a planetary alignment, and in a sense they are correct. This does not imply that the planets will be stacked up one behind the other like tin soldiers in a row, but, indeed, the planetary roundup will make a striking appearance for both urban and rural observers alike. Your best views will occur in that delicate late twilight period when light pollution and sky glow unobtrusively blend against a darkening landscape or cityscape. The next two StarWatch articles deal with this planetary congress and are posted with maps for downloading. The media already started its hype last week, a bit premature because Mercury doesn't gain marginal visibility until later during this week. Along with Mars, these two planets will be the key wanderers to locate because of dimness for Mars and closeness to the horizon for Mercury. Use binoculars if you have them. From May 9-16 the two farthest members, Jupiter and Mercury, are within 34 degrees of each other. A thin crescent moon passes the planets from May 13-16, adding a wonderful finale to this event.

296 APRIL 28, 2002: Planets Gather in the West: Developing over the past month has been a gathering of the planets in the west, right after sundown. Last week, only Mercury was missing from the group, but during the next two weeks, Mercury will join Jupiter, Saturn, Mars, and Venus to form a string of celestial gems visible in the darkening evening sky. In addition, with the proper observing gear, it would be possible to catch Uranus, Neptune, and Pluto in the morning sky around 4:00 a.m., and therefore observe all of the planets in one night without losing much sleep. A day with a deep blue sky, implying transparent air conditions, and a good western horizon are the key ingredients, along with binoculars that will allow you to observe the dusk gathering of planets successfully. I would suggest being at your observing post by 8:45 p.m. Venus, Jupiter, and Saturn will be easy to spot with only the eye. Mercury, and especially Mars, will present the challenge depending upon your visual acuity. A map can be downloaded from this week's web edition of StarWatch. Keep in mind that each evening will present a slightly different view. On Sunday the line up will be J-S-Mars-V-M. Jupiter will be highest, nearly halfway up in the sky. The other four planets will be grouped much nearer to the horizon and to each other. At 9:00 p.m. Mercury will be the lowest, only about one binocular field above the WNW horizon, but getting slightly higher as the week progresses. The line up with respect to brightness will be V-J-S-M-Mars, with Saturn and Mercury appearing almost identically bright. By Wednesday, Saturn and Mars are side-by-side. By Saturday, Saturn, Mars, and Venus form a tight little triangle with the greatest separation among members being equal to 3-1/2 degrees, a beautiful fit through binoculars.