John Pazmino
 NYSkies Astronomy Inc
 1992 June 1
[This report on the Pinatubo Dustdeck was issued in two parts in 1992 
May 1 and June 1. They are combined here under the later date. Minor 
cleanup done, otherwise the text is original.]
    The dust expelled-from Pinatubo last summer [1991] is still in 
the atmosphere and may be a longterm impediment to astronomy. Usually 
volcanic dust settles out after a few months, leaving the air clear 
and free for celestial observing. But Pinatubo's dust still circulates 
in the stratosphere like a veritable new dustdeck over the Earth. 
    In New York this dustdeck by day tempers the blueness of the sky, 
smothers the low Sun, reddens the twilights, and shows faux nuage 
effects. At night the stars are dimmed and the Moon is muted. 
    Pinatubo's dust hit New York on Friday 28 June 1991 in the late 
afternoon. Arline Caldwell and I saw the front creeping across the sky 
like a shroud over her Amagansett LI beachhouse. The daysky turned 
from normal blue to a dull grayish blue and the Sun set into a sandy 
    We were expecting the arrival any day from warnings posted by the 
press. However, the dust came in from the ocean and drifted toward the 
City -- it traversed Asia, Europe, and the Atlantic Ocean!! 
    While governments are chewing their knuckles against a potential 
global Hawks Nest syndrome, we here treat only of the astronomy 
consequences of the Pinatubo Dustdeck. 
    There was general fear that the dust would reach Mexico and Hawaii 
and impede views of the [July 1991] solar eclipse, then two weeks 
away. It in fact did cover these sites and hamper observations of that 
eclipse. Caldwell and I viewed from Waikeloa HI, but general overcast 
blocked the eclipse and masked any effects from Pinatubo. 
    Astronomers believed that, as with EI Chicho'n and St Helens, the 
dust would quickly fall out of the atmosphere to allow normal 
astronomy activity again. But Pinatubo is different. 
    Pinatubo is about the most violent volcano eruption of the 20th 
century. It heaved its stuff 30Km into the air, directly into the 
stratosphere, in stupendous amounts. Being that the stratosphere is a 
layered zone of the air, immune from weather and other convection 
forces, the dust is trapped and bound there. It circulates around the 
Earth for a long time, much like the CFCs. 
    As a result, Earth is now tunicked by a new atmospheric layer, the 
Pinatubo Dustdeck. It sits 30Km to 40Km up and is of rather irregular 
texture. This texture can be assessed from the ground and many readers 
are actually keeping records, if only casually, of it. 
    From New York the dust was not seriously noticed until the advent 
of the autumn clear sky season and the migration of sunset into the 
workhours. Then, in late October reports started coming into the AAA 
of a blue deficiency in the daysky and of some gorgeous sunsets. By 
November comments came in from layfolk -- not just astronomers -- 
about 'something wrong with the sky'. 
    The public's perception of the Pinatubo Dustdeck is of four grand 
categories: blue deficiency in the daysky, attenuation of the low Sun, 
reddening of twilights, revelation of the Moon's surface markings. 
    Simply put, since the eruption New York has not seen a truly blue 
sky. When the ground conditions and overall weather would normally 
generate dazzling brilliant blue skies, the best achieved is a limp 
blue. The horizon zone is always white or tan and the entire quadrant 
centered on the Sun is gray or tan. 
    Strangely, this aspect is more noticeable to cityfolk. They are 
shaded from direct Sun by the towers around them and can see pieces of 
the sky in comfort between them. The sky is just plain not really blue 
    When a thicker field of the dustdeck passes over, the sky is 
positively sand tinted with almost no blue at all in it. At noon there 
is a patch in the mid north sky of pastel blue and the Sun is ringed 
by a brown aureola. Occasionally the sky resembles a carpet, with 
'creases' or 'wrinkles"'. Since January [1992] this effect is much 
    The attentuation of the low Sun is mentioned mainly by motorists.     
They contend with the glaring Sun shining in their eyes during the 
evening and morning commutes in normal times. But now the Sun is not 
blinding anymore; it is merely annoyingly bright. The tinting in the 
windshield or ordinary sunglasses cut the Sun's brightness enough for 
comfortable driving. On almost any day the Sun shows a true disc, not 
the usual blazing painful amorphous light. 
    Virtually everyone mentions the beautiful vivid sunsets (and 
sunrises) over the City. As the Sun dips lower the sky in his quarter 
shifts to a red hue, mixed with what blue there is. The color ranges 
from a benign purple/violet on the clearest bluest days and the 
twilight resembles the ordinary ones. 
    On the dust-laden days there is so little initial blue that the 
sky flares out in lavender, magenta, flamingo, or coral. So striking 
is this that ordinary people stop at street corners and marvel at the 
    The common person is noticing the face in the Moon. Normally the 
Moon in town is too bright to casually discern her markings. Seen thru 
the Pinatubo Dustdeck she is tempered enough to reveal her texture to 
the public. Some people think they 'discovered' the markings and are 
amazed they can be seen from the ground. 
    At night the longer lightpath thru the dustdeck pretty much k11ls 
horizontal astronomy. The dust blocked easy viewing of Mercury at the 
March [1992] elongation and Nova Cygni under the pole in February 
[1992]. Both events would be readily visible under normal New York 
    The Pinatube Dustdeck interdicts star observation. On the whole 
the best of the clear nights suffers a loss of half a magnitude in 
transparency. The stars seem dimmer, altho the background is still 
dark. The dust is far too high to catch the ground illuminations from 
the City and augment the light veiling of the stars. So in an 
otherwise normal looking sky there are fewer stars! 
    We discovered an amazing anthropocentric and psychological 
phaenomenon. Under a dark sky with fewer stars some astronomers feel 
'frightened' or 'scared'. The missing stars, despite the otherwise 
normal appearance of the sky, makes them feel terribly isolated from 
the rest of the universe. 
    On the other hand, we learned that photometry, by eye and 
electric, is unperturbed by the dustdeck. Such photometry is done 
differentially, not absolutely. The target star is gauged against 
circumstant stars and all are, within a small area, uniformily dimmed 
by the dust. AAVSO, in particular, applies no 'correction' to its 
received assessment reports to compensate for the dustdeck. 
    What does the near -- and far -- future hold for astronomy under 
the Pinatubo Dustdeck? At best it is tougher to wage. At worst it may 
be subject to suspension from time to time.