SEEING THE MILKY WAY FROM NEW YORK ================================ John Pazmino NYSkies Astronomy Inc www.nyskies.org email@example.com 2002 September 2 initial 2003 May 25 current
Introduction ---------- It is still deemed impossible by some darksky leaders that to see the Milky Way from within the city limits of New York is a hopeless dream for some far off century. This is specially so as, with the reckless expansion of luminous graffiti in many other parts of the United States, the Milky Way is vanished from local skies. But the brutal fact is that the City of New York is scoring occasional and repeated sightings of the Milky Way within its praecincts, and has been doing so for at least a full decade. To be honest, only the very brightest sectors of the Milky Way, those in the summer reach, are so far reported. There is no thought of soon seeing the entire band arching across the sky. Furthermore, despite the slow steady improvement of the sky over New York, as yet the Milky Way is seen only from the outer boros, but not from Manhattan itself. In 2001 the first sighting was reported from the Bronx, the boro adjacent to Manhattan's northern frontier. The ability to see, even if only in the brightest sections, any Milky Way from the 'poster town' of deep-seated light pollution is one of the crowning achievements of the planet's darksky movement.
Milky Way seasons --------------- The main season for seeing the Milky Way from New York opens on September 1st and runs thru December 31st of each year. The start in date catches the clearest nights of the year, by climatic records, in the City during September and October. At the same time, the summer Milky Way, with its brightest segments, is still in the evening sky. By mid and late December, the summer Milky Way is in the west, sliding steadily into evening twilight, and the usual cloudy winter weather sets in. Milky Way sightings in this fall season were first logged in the late 1980s. Most years produced at least one sighting. Years ranged in score from zero, due to adverse weather, to four. A second season opened in the early 1990s but is not well established. This runs in May and June, which can bring some extremely dark nights. The Milky Way seen then is also the summer reach, in the midnight to predawn hours. Sightings in this season are far fewer, likely due to the inconvenient hours of visibility. Most years failed to score a sighting and the record is still too scanty to set firm limits for this new spring season.
What is visible ------------- A common misinterpretation of the City's Milky Way reports is that in some fanciful manner the full allsky band shines out, like in a country sky. This is pure silliness [so far in this century]. What is reported is a patch here and there along the Milky Way zone, disjointed from constellation to constellation, like slightly brighter islands of sky. On a particular night of reports, the precise descriptions can vary widely due to local circumstances. Collectively, they confirm that in fact the sky was clear and dark enough to let the Milky Way come thru. The general appearance is a swelling of brightness on the sky, fixed against the stars, and easily mistaken for a faint streak of cloud. On singular occasions some texture, like the edges of a cloud, are reported. Sections noted over the years are in Cygnus, Scutum, M24, M8. The extreme north and south limits of all sightings are Cepheus-Cygnus to Scorpius-Sagittarius. Sometimes the Milky Way is discernible to a particular observer for only part of the night, then it recedes into the grayed skies to total invisibility. The galactic center is not seen because of its low culmination altitude along the southern horizon. Definitely such sightings would a laughable brag for a darksky location. By the same token [EEeek!] they represent a true miracle from New York, giving hope and inspiration to darksky advocates.
Preparation --------- Because of all the extraneous illuminations in the sky over New York, it is very easy to mistake a 'normal' glow as a piece of Milky Way. Here are several factors to keep in mind about the Milky Way. It stretches along a fixed circle in the stars. The summer reach, the only one so far seen from New York, runs from the southern horizon in Scorpius, then northward into Sagittarius, Scutum, Aquila, Cygnus, and Cepheus. I miss out lateral extensions into other constellations. You can check this on a staratlas which plots the galactic equator or centerline of the Milky Way. Define a belt, say, 10 degrees wide straddling this equator and that's the region of sky you have to look at. It can be marked out on a planisphere, so you can know where over your horizon it is sitting at the moment of observation. A bit of pencilled shading is all that's needed on the starplate. As an example, you will not see the summer Milky Way in the predawn hours in the fall season; it is too low in the northwest. To see it in the new spring season, you have to be under the stars in those hours. It then runs high in the east to overhead. The Milky Way is also of a fixed brilliance, so you can gage by the surrounding sky what chance you have for seeing it. This feature makes the Milky Way a more certain target than an aurora, which may be of any brilliance.
Transparency ---------- To see the Milky Way you need absolutely no worse than a cold 4.5 magnitude transparency in the Milky Way itself. Not for the overhead or darkest part of the sky, but where the Milky Way sits. Not rounded down to 4.5, but a hard and cold needle-pinning 4.5. This is a minimum but insufficient condition before being rewarded with a glimpse of the Milky Way. The fainter stars you can see, the better are the chances. Have with you a chart of the Milky Way zone with key stars labelled with magnitudes. A computer planetarium program can make one up for you.
Viewing location -------------- Because you'll be watching with unaided eye for only a couple minutes, the selection of viewing site is vastly more ample than for regular starviewing. It can be a darkened stoop, alcove, corner, terrace, park. Any place you can walk into, be aware of your surrounds, and inspect the sky in peace and quiet. You may, for instance, find a shaded patch in a park along your walk home from work or get permission to use your house's rooftop after arriving home. There need be no conveniences at the site being that you are only momentarily stopping there. Lack of benches or warmth (autumn can be awfully raw!) is no issue. Pull up your jacket collar and lean against a wall.
Binoculars -------- They will better align you with the Milky Way, pick out the fainter stars, and assess movement of the suspected spot against the stars. One clue to a false Milky Way patch is that in binoculars it still looks like a cloud and not sprinkled all over with tiny stars. However, it is the view of the Milky Way by the eye alone that counts.
Ground illumination ----------------- The main criterion is that local lamps be out of your face. At street level, even in the nabes of the most star-friendly outdoor illuminations, you will be hit by excess light beams. These come from residual trashlights on buildings, car headlights, old streetlamps. The site must be shaded from this clutter of ground illuminations. Blockage by trees (when still in leaf), walls, fences are the easiest to look for at a street location. Elevation above the street is best for a terrace or rooftop. It seems that once you're a couple floors above the street lighting, the grosser interference from these lights is below you. This strategy exploits one of the eerie features of New York. It is a 'dark' City in that there is little exterior lighting above the first few floors and no extreme lighting of towers. It may be feasible to construct a portable light shield to set up at your site. Observers have used folded refrigerator boxes, Chinese curtains, blankets draped on railings and fences, jackets with 'snout' hoods. One fetching possibility is an el platform, practicly unique to New York. These sit six or so meters off of the street, above almost all street-level lights, and are themselfs modestly lighted. View form the ends, away from the canopy.
Sky exposure ---------- Your site must face the part of the sky where the Milky Way runs! Be wisely of compass directions at the site, particularly if the street grid is skewed against them. Study a street map. Ideally you want the entire zone as much as the instant day and hour allow, so you can catch any part of the Milky Way. Recall from above that it shines out in isolated spots here and there. You could miss one by an ill- placed obstruction. Such an ideal place may be found in an open part of a park or higher rooftop or even a shaded corner on a hill. In praticality, you'll use the location of opportunity, which may well occlude major parts of the sky. Just try to get a much of the Milky Way path in your sky exposure as possible with preference for the high altitudes, where the air is clearer and darker.
Dark adaption ----------- It's impossible to get really dark adapted anywhere outdoors in New York. You can achieve a good adaption, sufficient for hunting for the Milky Way, by closing your eyes for a minute or two while shielded from local lights. If feasible, lie in a lawnchair or sit against a wall with closed eyes. Do this after checking your vicinity for the usual hazards of big city life. A trick that works for some people is to stand upright, look down at your feet, close your eyes, and swoosh the eyeballs left and right rapidly. When you, with dark adapted eyes, leave your observing spot you may for a few seconds be dazzled by the street lights. Be ready.
Darkness and clarity ------------------ For the conurbation that is New York, with 9-1/2 million residents and an other 12 or more million in its satellite towns, the City is amazingly friendly for stargazing. It rid itself of aerial dirt and soot in the 1970s by curbing smokestack and tailpipe emissions. Traditional factories transmorphed into offices, which emit essentially no obnoxious material into the air. Electrification of regional rail and factories also reduced such contaminants in the air. New York is the living atlas of the darksky for examplifying ways to conquer the scourge of luminous graffiti. Street after street illustrate the strategies and tactics to remove or reduce excess skyward emission of light. True, this largely is accomplished by the continual renewal of the City, with the replacement structures built to the modern mature standards of illumination. The end result is that on Manhattan the normal clearsky transparency is fully fourth magnitude, with frequent dips to 4-1/2.
Sky illuminations --------------- You must be intimately familiar with the artificial illuminations in your sky to avoid false Milky Way sightings and to cut down on wasted trips to your viewing site. Know the patches of sky brightness from nearby properties. Bear in mind that these hotspots can be very localized and may change location, size, and intensity from block to block. It's the situation at your viewing site that's critical. Be wisely for temporary or occasional illuminations, like a ballgame, political rally, street fair.
Overall chances -------------- High mist or haze, unnoticed casually, will block the Milky Way on an otherwise clear dark night. So will the least excess of grayness, a Moon still in sky, lingering twilight. On the whole it is a touch and go effort with most shots being duds. Most of your inspections will turn up nothing of the Milky Way on the nights when the chances do look favorable. When sighted, as gaged by reports collected so far, the Milky Way is a threshold feature recognized by its fixed place in the stars. Wait a minute for any drift against the stars; you may be seeing a thin cloud. High airplane contrails would likely be too narrow and they dilate and fade over time. A reflection of the Moon onto a high elevation haze layer can fool you. All in all, you can be frustrated and discouraged by not seeing the Milky Way despite taking all the precautions noted here. It may be that after all your peculiar location is just too hostile for the Milky Way, as so far is the case on Manhattan itself.
Confirmation ---------- First we consider the outer boros, off of Manhattan. As long as you are sky wisely, take the care in looking, and are overall a good bloke, your report is valid. It would be well to call an other astronomer to check your sighting, but for the outer boros this is not a necessity. Usually multiple reports from a given night and boro are wholly independent of each other. Manhattan, on account of its grand importance in the darksky movement, requires a tighter rule. Yet even here it has to be loose. As long as within the same night two persons see the Milky Way from Manhattan, the report is 'confirmed'. The two sightings may be from different parts of Manhattan and at different hours of the night. Such a lax test accommodates the general impracticality of having at your side an other astronomer when you check for the Milky Way. A single report from Manhattan is noted as 'unconfirmed'. Not that there is real doubt about what you saw, but merely that there was no second report for that night. The lack of a confirming report can be due to several perfectly respectable reasons. These include unfavorable conditions at the other person's site or absence of the person from observing. It would be wise to team up now with an other astronomer, like those here in NYSkies, on Manhattan as a check on your sighting. This person may be anywhere else but reasonably able to recognize the Milky Way from a favorable location.
Where sightings come from ----------------------- In the early years since records were kept regularly in the late 1980s, sightings came from a zone of New York generally south of the glacial moraine. This is the southern boundary of the last Ice Age and is manifested by the ridge running roughly southwest to east thru the entire City. The ridge extends into New Jersey and onto Long Island. Along it are the various nabes with Heights, Hill(s), Slope in their names. Traditionally, heavy industry with smokestacks congregated north of the moraine along the harbor and rivers fronting Manhattan. These poured out air pollution which the moraine for the most part held back from the southern parts of the City. South of the moraine was mostly residences with minor contribution to air pollution. In spite of the steady evolution of society away from heavy air- polluting industry in the City, this situation still prevails to a substantial degree. The real betterment comes from the gradual removal of excess trashlighting as factories are rebuilt. Many are now being converted to nonindustrial uses with far less trashlighting. Hence, the darker skies of New York are in this southern zone, from mid Staten Island, the Narrows, mid Brooklyn, and mid Queens. The zone to the north, including Manhattan and the Bronx, have the typical mediocre urban skies with no Milky Way. Milky Way sightings elude Manhattan, the Bronx, and large parts of the other boros. In 2001 the City scored the first sighting in recent memory from the Bronx. This may be a spinoff of the extraordinary clear skies following World Trade Center. For many days the entire aviation industry was grounded, freeing the air of airplane pollution. A subsequent sighting occurred in 2002 August from the Bronx, with a more or less normal aviation activity.
Manhattan? -------- Manhattan remains the only boro for which there are no Milky Way sightings as yet. It is very unlikely that the current season will yield a sighting because the quality of air is substantially the same as that of last year. Never the less, it pays to keep an eye out for the Milky Way, even tho for sure you will turn in only negative reports. In 1999 as part of the approaching millennium astronomers in New York set themselfs the goal of seeing the Milky Way from Manhattan by the end of the decade. That is, by 2010. With World Trade Center, the ensuing disruption of normal city life, and a general slump in the national economy the deadline is informally extended to 2012, the year New York [hopefully] hosts the Summer Olympics. It is certain that only select parts of the Island will be blessed with a sighting, someplace like Fort Tryon Park or the new Hudson River Park. And it is certain that only one particularly bright segment of the Milky Way will be spotted. When that happens, the war against light pollution is over. We won.