SEEING THE MILKY WAY FROM NEW YORK
================================
John Pazmino
NYSkies Astronomy Inc
www.nyskies.org
nyskies@nyskies.org
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.