top of the lawn
urban footpath | pavement | sidewalk astronomy from Central Park, New York City
Tuesday, January 23, 2007
Monday, January 22, 2007
Geology of Drip Rock
A few months ago I read a delightful online book and then followed two of the tours verbatim providing a leisurely program of Central Park geology. To make the tour's more convenient, I downloaded & viewed the webpages to my Newton MessagesPad 2100 with Steve Weyer's Newtscape browser and bookmaker/reader. With a small fanny pack Nikon CoolPix 995 and Newton were both tucked away securely as I romped and roamed over the glaciated roches moutonées.
As a result of this I am more acutely aware of the many outcroppings that abound in Central Park. It's like when never noticing the families and children on the Upper West Side until my wife and I started our family. From where did all the strollers come?
Take for instance this photo. Here one can see an erratic, a boulder picked up from the north somewhere and carried down and deposited in Central Park by the Wisconsin ice sheet. Well that's the definition of an erratic but I would be careful to apply it to these found throughout the park. Granted they are large and probably just as heavy but with the blasting out of rocks for nearby roads and walks, I suspect some probability that the landscapers thought it a nice touch.
Drip Rock is a common Manhattan Schist outcropping like the many seen all about the park. It's a pedestal that stands above the moving crowds and horse carriages. Stationary atop of the rock with telescope pointing to celestial south-southeast, the world turns, and daytime astronomical events reveal celestial glories above a horizon of skyscrapers. Now that I've imbibed on some geological awareness, a huge granite dike presents itself at my feet. For the uninformed it could go unnoticed as concrete filling.
This granite dike is an intrusive igneous rock consisting of the minerals feldspar, quartz, and mica. It has a speckled appearance to it. There are two types of granite, granite and granite pegmatite (pegmatite for convenience), and they are distinguished by the size of their grain. The granite grain is smaller and finer, having resulted from rapid cooling. Geologists have determined that the igneous material was injected in to the crevices of a host rock which lost most of its heat.
At the end of the granite dike there are veins of raised, threadlike lines continuing away from the dike, likewise cutting across the grain of the rock. Two can be seen running parallel to the fracture in the rock. Hanley and Graff point out that "
these are veins of quartz thought to have originated when scalding, silica-rich fluids were forced by subterranean pressure into hairline fissures in the rock.These fissures can be observed throuhout the park on many outcrops, larger and small.
Pegmatite, on the other hand, has larger grains, which the heated host rock provided time for the grains to grow larger. The larger, coarser grains of pegmatite are just as easy to recognize as a foreign object in the schist as the finer granite and can have a pinkish or whitish color.
Manhattan schist exhibits a foliation include that is typical of metamorphic rock. Simply the rock displays a direction or grain. The igneous intrusions can cut across the grain, known as dikes, or run parallel, called sills. Most that I have noticed are dikes like the one illustrated previously.
This large band on the southside of the outcrop to be a granite sill as it is folded into the direction of the rock's grain.
Books of Interest
Hanley, Thomas and M. M. Graff. Rock Trails in Central Park. Greensward Foundation, Inc. 1976.
Raymo, Chet & Maureen Raymo. Written in Stone. Black Dome Press Corp., Hensonville, N.Y. 1989.
Schuberth, Christopher J. The Geology of New York City and environs. Natural History Press, Garden City, N.Y. 1968.
My favorite Central Park map.
- Note to find Drip Rock follow E 62nd St., marked near the lower left corner, across the Park passing Center Drive. Drip Rock is labeled. Across the street to the south is Cop Cot, another area that I use for daytime observation. Nearby my daughter and I catch-n-release fireflies, giving this location a household name Firefly Garden.
Sunday, January 21, 2007
20070120 - Winter Messier objects with small optics
Session name: 20070120.2035
I showed up last night at TotL to observe with small optics. I began work compiling a list of results in observing the Messier objects in urban conditions with various optics. Others have done this and Tony Flanders' is the one I know best from his Sky & Telescope article and also his astronomy website. I intend to do a similar list with optics ranging from handheld bins to the 10" reflector limited to observations from TotL.
The night was pretty cold 16°F/-8°C, gusty at times with a clear, moonless sky. Naked eye,I could make out 12 stars of Lepus from tail tip to 3 stars of his ears. 4 stars of Columba were visible, the fifth one that is east of two central bright ones was difficult to resolve.
This session I had the Coulter CT-100, Takahashi bins, and the Fujinon 7x50 FMTR-SX Polaris. The plan was to swap the CT-100 & Tak bins on the Bogen 410 but the cold made use of the Bogen geared head difficult to use especially with gloves on so I just mounted the CT-100 and never unpacked the Tak. A Tele Vue 20mm Plossl was used exclusively with the CT-100 resulting in a 2.3° field of view and 22x magnification.
In handheld 7x50 bins, M35, M36, and M37 were apparent, in order of ease and resolution. All were soft, unresolved glows increasingly lower contrast with sky. M38 was not detected. M41 is easy with a few stars resolving and twinkling. In the F/4 4¼" reflector, all the clusters resolved with no issue. In the scope M37 is much more concentrated, desne with faint stars.
M45 and M42 were both seen without any problems, M43, not. Of all these, M45 was naked eye and "something in funny in the state of denmark" applies to M42 as one looks at the sword.
M1 & M46 were expectedly undetected. M47 was easily seen, small, sparkling. Of all the clusters, I prefer M47 in the handheld and even the Coulter this open cluster is attractive.
Since it was pretty cold and the wind could pick up pretty strong, I ended this little project earlier than expected. Is isn't often that I'd pack up early on a clear night but with equipment not being cooperative and a bit off my game I figured another opportunity will come.
20070120 - Daytime Crescent paired with Venus
Session name: 20070120.1310
I stole away at lunch yesterday with Tak backpack to look for the young crescent moon. At this time she's already 1 day 14 hours past New Moon. Initially I thought this was to be a cinch. Since I am surrounded by buildings that rise, in some cases, to 60° ~ 70° in elevation, I went first to Cop Cot and then settled at Drip Rock. Since I couldn't see it naked eye I thought that the buildings were obstructing the view.
The Sun's apparent path across the northerner's winter sky is low, and so the ecliptic too is low. Shadows mute most of the cross streets and avenues can suffer the same. The Sun just can't peek high enough to shine his glory down.
I measured off from Sun with outstretched hand and then scan the sky with the handheld bins. In the handheld bins spotted the young crescent pretty quickly and was surprised by the low contrast. I would have thought the 3.3% illuminated crescent to be brighter and greater contrast with the sky. It was darker than passing clouds and in a queer sort of way provided contrast that kept it visible with thin filaments of clouds passing over.
In the field of view, Venus sat up around two o'clock and the Moon was around eight o'clock and LARGE. In spite of its size, its brightness did not contrast sharply with the pale bluish white background sky. On top of the clouds were passing through at as regular clip, sometimes thick enough to snuff out Venus.
As I observed, I couldn't help but think of those record holders who observe crescents as young as 15 hours - even younger! I'm under the impression that these sightings didn't have the advantage of having a bright planet nearby as a convenient landmark. One has to have this kind of experience where one can scan a field of view and allow the eye to find and focus across the field of view, just as repeated tennis lessons develop muscle memory. I looked away on occasion just so I would have to recover it - a kind of volley.
Two passersby took turns at the eyepieces of the Tak bins. I described what they would be looking for and each said after some time of closing one eye, moving their head about, squinting with both eyes that they saw the Moon. I had a feeling it was Venus because that is much brighter, and once resolved easiest to see in the field of view. I suggested that they look for a large, low contrast crescent on the other side. Soon enough they got it. They hadn't a previous mental experience to identify the crescent moon. They were both both shocked by its faintness and large size. Each had found it with a Eureka! feeling.
Saturday, January 20, 2007
My sixth field observing logbook is nearing completion. There was a small deviation from the typical Moleskine Pocket Plain Book I love to use. Because the binding is on the short side for the Moleskine Reporter Style Pocket Notebook I thought in terms of landscape as opposed to portrait. I thought I would have more freedom to use the paper in a long 11" x 3.5" rather than 7" x 5.5". It turns out I am not a fan of that one and can't wait to complete the 5 pages that remain.
I'll return to the standard style.
But what about the price? At Border's Books, they sell the Reporter style, $9.95 printed on the Moleskine label on the back. They don't have the portrait one in stock. I go to a stationery store where they do carry both and they sell for $11.95. No price printed on the Moleskine label, just a white sticker. Wanting to purchase locally rather mailorder, the Reporter shows up and the price ranges ranges between those two limits. Only one place I found the regular one.
I have a couple new Moleskines stashed but of Reporter and larger size. I want to remain married to the book I adore. Gotta make up mind quick and act!, unless the weather continues to be overcast.
20070117 - Rasky Tables
Session name: 20070117.2035
Since 2003 I purchase the Royal Astronomical Society of Canada Observer's Handbook from John Pazmino. I see it often referred in print as the "OH" and hear it called the "Observer's Handbook", but for reasons unknown or forgotten I call it "Rasky". The 2003 copy has a few notes scribbled in on the margins of some All-Sky maps. That copy timestamps the year when my earnest observing program began in the Fall.
2003. October 2003. (in the same vein as Bond.)
In the following years, checkmarks accompany notes in the margins of two sections in the Chapter NEBULAE AND GALAXIES, both written by Alan Dyer. The sections, The Messier Catalogue & The Finest NGC Objects, contain tables organized by season. I use them as convenient checklists for DSO objects observed. The intent is to check off objects observed only from TotL.
With this in mind, I planned to journey in the Winter Sky led by Rasky. The Messier objects in the table listed are, in order of right ascension reading columns across:
Three objects in the list above are very challenging. I won't call them impossible because two of them just required larger optics to finally get captured. From the middle of Central Park I have seen all but M1, M46, and M78 with the Takahashi 4" refractor. It took the Teleport 10"reflector to add green ticks to M1 and M46. To date, I have not observed M78 from TotL or anywhere else. Most of the open clusters, except M46, have been observed in optics as small as 7x50 binoculars, even handheld.
My favorites on the list are M1, M42, and M37. Noteworthy is the background Milky Way sky around the Aurigae clusters. We can't see, at least haven't seen, the Milky Way from TotL but in the eyepiece I can see and feel the grainy, whitish, background. I don't know if I would use the word nebulousity but I wouldn't hesitate to call the sky crunchy.
This session I was surprised not to have resolved M1 confidently. Similar to a session in late December with Kin, I suspected a spot in the 1.1° field of view at 75x. Even though I sketched it where I thought it to lie relative to the field stars, I can't say I absolutely saw it. There have been only two TotL sessions that M1 was positively observed by myself and others, no filters in each case. M78 continues to remain quieter than contrast permits.
M46 strikes me as similar in character as M37 though fainter and slightly less dense. They are both pretty large and rich with faint stars. At 25' that is just smaller than the Full Moon. In all my TotL observations, the planetary nebula, NGC2438, in northern part of M46, escapes detection. I can recall sessions at the other end of the lawn, TPO, where Ben & I would scour the sky around M47 hunting for this cluster. There is a distinct obvious red star on the trail between the two but the other end was always empty, until TP10's glass turned on it. I have since returned with the 4" only to resolve the 2 or 3 brighter stars that lie in a NW-SE line on the SE edge of this cluster. Without having seen the cluster, the faint light of the hundreds or thousands of stars that expresses this type of nebula, resists discovery.
I bounced around the sky a lot. In spite of the absence of other TotL'ers, about a dozen and half people still passed by, stopping to have peeks through the scope. Early on M41 or M42 were the two objects I put most in the eyepiece and I provided the soundbite of "the leaves in the river" description for open clusters or the stellar nursery for the Great Orion Nebula. Later, others would be treated to a marvelous view of Saturn with 3 moons aligned to the west. In all 5 moons were observed including Enceladus hugging the inside track almost in line with Tethys, Dione,and Rhea. The disk's shadow becoming a black hairline but still greater than fine line of Cassini Division. (Is opposition close?) Since I was in Leo at one end of the Sickle, I pushed the scope up to the other end, checking on NGC2903. I took in the view of a very small, very dim, low contrast nucleus but didn't dare share this after showing Saturn.
Occasionally, I deviated from the Messier list observe other nearby NGCs. Leaving M35, a worthwhile open cluster in both bins and scope, I pulled the scope down and nudged it east to NGC2392, the Eskimo Nebula, treating my eye to color and the blinking effect. From M93, I pushed the Dob west into Canis Major to observe NGC2362, Tau Canis Majoris Cluster. This delightful little open cluster nestles the bright tau CMa in a arrowhead-shaped nest. Like most open clusters, I prefer to observe them in low power, wide field. Just my preference but I like the blushing, unresolved glow that they can display. Sometimes the scope just blows them apart where a different kind of study is performed.
I won't give up trying to check off M78 in the winter sky table, as I didn't with M1 and as I don't with M110. I'll try and try hoping that I happen to be looking at those two faint stars when all the factors are favorable and a faint nebulousity paints the sky. I don't expect the Wow! factor other than filling the red square with a green check mark.
Friday, January 19, 2007
did i have a chance?
Session name: 20070119.1650
This goal of this session was to observe the 18 hour 10+ minute waxing crescent moon. Did I have a chance? Not the slightest - a deck of clouds covered the horizon from as far north as I could see past west, all the way down into the south. From what I could tell Sun set further north of Statue of Liberty, but it was cloaked beneath that thick, dark quilt.
The Sun set 4:57 EST. The sky clear above 20°. My hopes that this would drop down to 2° were unrealistic. With fist extended at arm's length I looked for Mercury's flame. Extending pinky and thumb, keeping my hand twisted on 10:30-4:30 line I searched for Venus. With handheld bins I scanned above the horizon looking for each. The cloud deck climbed too high in the sky. Venus, at this time, was to be a bit better than 15° in altitude.
Civil twilight began at 5:27 EST. As I swept the 7.5° binocular field of view along the horizon and ogled Lady Liberty, a brilliant light appeared higher in the sky. Venus at 11° was ablaze and stayed in the clear for about 2 minutes. I looked higher in the sky where the clearing continued. Hyades and Pleiades were visible naked eye, contrasted on a darkened turquoise velvet. While struggling with the gusty wind trying to turn the pages, hurried notes were scratched in the logbook. I looked back up to take a count of the how many Pleiades I could count but the show was over. It was only moments.
Off to moonwatch to file a report and tally my scorecard at 0-1.
not my time with McNaught
I missed the whole McNaught thing, observing wholly on the Internet.
This past Tuesday (1/17), Ben a fellow TotL'er issued an unexpected invite to observe daytime McNaught. I was sort of caught off guard not knowing where the comet was or if it was daytime object. Work has occupied a better part of my days that I didn't think I could steal away at lunch. As luck would have it, time freed up and I met Ben at Bryant Park. He had his TV-76 and I with my Takahashi bins.
In short, Bryant Park was not an agreeable place since the horizon consists of rooftop cornices rising easily to 30° in the lower parts. Tree branches confused the field of view with the unfocused shadows tangled with the bluish, white sky. Ben & I tried from various spots with the park but we agreed that if it was visible it was below the rooftops.
Kin would report later in the day that he was unable to see it in binoculars from Union Square Park. I assume his horizon was better.
When we abandoned that hunt, our attention turned to Venus. In the scope, binoculars, and fleetingly naked eye we stood and observed Venus while talking of old & current times. I didn't turn my attention to Mercury and I pretty much ignored the Sun, using our star as a landmark to measure off to Venus - almost a full handspan, pinky to thumbtip (then curl thumbtip in to subtract 2°) separation.
I have missed events in the past primarily due to weather. This year it was due to schedule and priorities - hmmmm.
Tuesday, January 16, 2007
forecasting crescents in 2007
Chasing the crescent moons.
Chasing crescent moons is becoming a favorite pastime for me. The challenge of "can we detect it or not?" is addictive. Catching both crescents that embrace the New Moon. Knocking on the door of a 36 hour interval between the opposing crescents. Anticipation that nature agrees with my perseverance. However, being in the right place at the right time is true way to challenge the physically possible. Earth, Moon, Sun and obliquity of the ecliptic all play a role. It's a confluence of circumstances which the Babylonian astronomers were aware. But for us New Yorkers, most times that right place/right time is somewhere else on the globe.
The best interval for opposing crescents this year with the slightest chance of success is 37 hours 24 minutes. In the Astronomical Calendar, Guy Ottewell reports that Stephen J. O'Meara holds the naked eye record of 35h 42m and the binocular record goes to Don Pearce 35h 14 m. Nonetheless what follows is where we observe and my predictions for this year. Naturally, these are for weather permitting dates.
Favorite spots to observe these events are
- Carl Schurz Park at 86th St. for old crescents rising in the wee hours
- Great Lawn, Central Park, somewhere along the eastern sidewalk for young crescents setting shortly after the Sun
- Battery Park, near the East Coast Memorial for really low western horizon for young crescent
This year I am making some predictions. Last year I was able to come within the intervals measured in minutes for those crescents observed. Sometimes Charlie caught it first, other times I did, but in all cases we all observed it. If I remember correctly, even pedestrians we share the oculars with had seen it. On one young crescent event I claimed to have seen the crescent naked eye but Charlie and Kin had not.
Beginning 2007 Daylight Saving Time (DST) will begin on the second Sunday in March (11 March 2007) and end the first Sunday in November (04 November 2007). This is a result of the Energy Policy Act of 2005 that President Bush signed on 08 August of that year.
Bracketing the New Moon
16 Apr & 17 Apr
Interval - 37h24m
14 Jun & 15 Jun
Interval - 39h
16 Apr :: predicted sighting 05:45 ~ 05:50 EDT
Age :: 28d7h (-25.3h prior to New Moon)
15° 29' W elongation
Easy; altitude at predicted time 1° 07'
14 Jun :: predicted sighting 04:40 ~04:45 EDT
Age :: 28d13h (-17.7h prior to New Moon)
11° 39' W elongation
Moderate; altitude at predicted time 1° 41'
10 Oct :: -predict no sighting-
Age :: 28d21h (-17.9h prior to New Moon)
In terms of absolute age, this crescent will be the closest to a New Moon observed in y2007
19 Jan :: predicted sighting 17:10 ~ 17:15 EST
Age :: 18h09m
10° 22' E elongation
V. Difficult; altitude at predicted time 2° 58'
19 Mar :: predicted sighting 19:10 ~ 19:15 EDT
Age :: 20h26m
12° 17' E elongation
Easy; altitude at predicted time 9° 44'
17 Apr :: predicted sighting 19:50 ~ 20:00 EDT
Age :: 12h18m
8° 16' E elongation
Extremely Difficult (why not % D); altitude at predicted time 4° 01'
15 Jun :: predicted sighting 20:50 ~ 20:55 EDT
Age :: 21h24m
12° 50' E elongation
Easy; altitude at predicted time 6° 30'
Monday, January 01, 2007
Bringing in the New Year - 2007
Happy New Year from the Top of the Lawn.
With my family abroad, I chose to celebrate the coming and celebration of the New Year with Team TotL and others that we regularly meet. Mark brought the champagne and Basque port with some beautiful Turkish glasses. His wife stayed in the warmth of the car until the last minute before the fireworks went off.
Charlie, Kin, Mark, and I lifted glasses to the start of the New Year. In contrast to the thousands that I left on my street, I met Charlie about 11:15pm, he was all alone and looked a bit cold as I approached. Kin would arrive by bike and Mark came walking up from the west and eventually hundreds gathered.
The geese and ducks flew north against a white, tufted backdrop thick enough to hide Moon's location. Not even a hint. Andy & Masha, even though he suggested this the night before, were missed from our little cluster among the other stellar groups. Reliably, Carol & Doggey passed by and exchanged greetings.Everyone cheered and applauded with each burst of light over the city skyscape.
Since I have spent a considerable amount of time with these folks and I consider them close as family, it made sense to share the celebration with them. I wish everyone a happy, healthy New year with many clear, dark nights.