John Pazmino
 NYSkies Astronomy Inc
 2015 November 26

    New York in 2015 entered a new season of lunar occultations of 
Aldebaran. As the Moon sweeps thru the zodiac, she passes over or miss 
stars according as the lunar ecliptic latitude and the observer's 
location on Earth. For many years the Moon missed Aldebaran. Now she 
is in a run of almost monthly hits, altho some ae not seen from the 
City by timezone or geographic latitude. 
    The occultation on Thanksgiving morning, 26 November 2015, 
occurred in clear chilly air.  The Moon was almost full and was low in 
the west at the start of dawn.  

    For this event I needed a a window facing west with no 
obstructions like trees or roofs.  Of a couple choices, one window was 
perfect with the Moon in open sky over low skyline.
    I observed from indoors, to avoid the hassles of setting up 
outside so early in the day. My plan was to watch the occultation, 
then turn back to bed for a few more hours of sleep. 
    At the window on the preceding evening of the 25th I moved an end 
table under the sill to support a table-top telescope. I set the scope 
case next to the table, ready to unpack it quietly and quickly in the 
dawn hours. 
    Because my cats roam around at night I dared not try to view thru 
a completely open window. The pets jump to the sill and could easily 
slide off with no positive barrier to contain them. In the stead, I 
 then washed the inner glass pane and  then latched open the screen 
and outer glass panes. I finally closed the inner pane, protecting the 
cars and giving me, hopefully, a clean view thru it of the 
    I placed a small folding chair next to the end table. My observing 
station was now ready to rumble. Eons ago I learned that observing 
must be done, in so far as practical, under comfort. On the whole, 
being seated at the telescope is a huge step toward that comfort. 

At my station 
   I got up from sleep at 5 AM and dressed in running slacks and 
sweater. The air was thoroly chilly but probably not freezing. I threw 
over me a heavy wool bathrobe. I  went to the window in dark to keep 
my night vision.     
    The sky was clear. I didn't purposely hunt for stars. I did notice 
the Pleiades to the right of the Moon. The Moon, being shortly after 
full phase, was dazzling. I could not see Aldebaran at all by eye. 
    I unpacked the scope and set it on its drum base onto the end 
table. I never thought of attaching its equatorial stand because I can 
follow the Moon by the axis control knobs. I rotated the eyepiece to 
face my chair and sat down. 
    I got the Moon in the eyepiece right away. She was almost 
blinding! I scanned the disc for any limb shadow, didn't see any, and 
browsed around at the rays and spots here and there. 
The occultation
    here was Aldebaran a good way left of the Moon. It was a lucid 
twinkling point. No other Hyades stars were noticed. 
    I was looking thru a single sheet of window glass that made some 
distortion in the image. I found that the most pleasing view was with 
low power, covering the whole lunar disc. Higher power merely showed 
more window distortion. 
    On & off for the next half hour I checked on Aldebaran. The axis 
knobs helped me to chase the Moon as she drifted out of the field. 
    Aldebaran creeped closer and closer to the Moon's eastern edge. I 
mean astronomical east, the leading, edge  The sky was starting to 
brighten with dawn. 
    At 5:46 AM EST, by a wall clock, Aldebaran snapped out of sight 
behind the Moon. I think it was gone a second earlier as twinkling 
sometimes blanked it out momentarily. After a few more seconds of 
inspecting the lunar edge, I knew the star was in fact behind the 
Moon. I didn't try for a proper timing of the ingress, preferring to 
enjoy the view at leisure. 

The wait 
    Aldebaran would return to clear sky in about 45 minutes. As I laid 
down to rest in bed, the sky continued to brighten. By a quarter after 
six, again by the wall clock, it was obvious that the sky was already 
too bright to see any stars. The Moon was still in open sky over 
roofs, a lot easier to examine with a bright sky around her. 
    The surface markings were far easier to study with the lunar glare 
abated by dawn.As a matter of technique, many astronomers observe the 
Moon in twilight to suppress the dazzling of full night. 
    I called it quits since thee was for me no hope of spotting 
Aldebaran at the egress.

Closing the station
    I made sure my cats were no where near me and quickly opened the 
inner pane, pulled down the screen and outer panes. Then I closed the 
inner pane. I packed the scope, whose case was near the radiator. Heat 
for the house wa starting to come up. 
    I left the packed scope by the end table and went back to sleep. A 
couple hours later, in bright morning daylight, I woke up for the day. 
put away the scope case and straightened the table, removed the chair. 
The cats were already scampering around for breakfast. 

    The almost Full Moon for this occultation set shortly after 
sunrise. Was this a selenehelion? Stricta mente it wasn't because a 
classical selenehelion requires that the Moon be in eclipse when seen 
together with the Sun at sunrise or sunset. We had a true selenehelion 
in New York during the 8 October 2014 lunar eclipse at sunrise. The 
sky near the Moon was mostly cloudy, spoiling the view for most 
observers in the City. 
    By a relaxed definition the Moon seen with the Sun at sunrise or 
sunset may be within a stated tolerance of the exact Full Moon. Under 
this definition we can have several selenehelia each year. 
    I mysyself allow +/-6 hours centered on the Full Moon hour. The 
tolerance for relaxed selenehelia is  a personal choice but it can not 
excede /-12 hours, else the Moon is really too far from Full phase. 
    For the Aldebaran occultation the Full Moon occurred on 2015 
November 25 17:45 EST.. Even adding the maximum reasonable  leeway, 
+12 hours, this gives the latest hour for a possible selenehelion of 
05:45 on the 26th. This happened to be, wholly by coincidence, when 
Aldebaran entered the occultation. By sunrise, 06:54, the window for 
selenehelion was closed and the Moon herself set at 07:20. 
    We did not have a selenehelion for the Aldebaran occultation. We 
did enjoy a very large Moon setting some 35 minutes after sunrise. 

Aldebaran occultations 
    I noted that we are in a new season for occultations of Aldebaran. 
Stars along the zodiac are occulted only if the Moon's orbit swings 
her over the star as seen from Earth. The lunar orbit is inclined 
about 5-1/2 degree from the ecliptic, with the Moon completing a 
circuit of latitude +/-5-1/2 degree per month. The 'month' is NOT the 
sidereal or synodic month. It is the draconic month, the period 
 between successive crossings of zero degree latitude, either on the 
northward leg of the orbit or the southward. 
    These zero points, the nodes of the orbit, migrate westward thru 
the zodiac, against the order of the signs. The Moon crosses a node a 
little early relative to the sidereal month. A full migration of the 
nodes , a sliding of the whole orbit, takes about 18 years. 
    The effect is that a star in the zodiac within the latitude 
corridor of the Moon is occulted in certain years and is missed in 
others. The interval between occultation seasons is about 18 years. 
The season lasts from only a couple years  for stars far from the 
ecliptic, near the limit of excursion of the Moon,like for Aldebaran. 
    The current season of Aldebaran occultations began with the event 
of 2015 January 29 and ends with that of 2018 September 3. This span 
covers all occultations over the whole Earth, not just for New York. 
    New York misses most events for latitude and timezone 
displacement. Those geometricly visible from the City are listed here: 
     T date and hour   | %SL  | EST | Sun | star | Sep' 
    05 Sep 2015 05:22 | 52- | 23:19 | -42 |   7  |  9 low alt 
    02 Oct 2015 13:03 | 74- | 09:30 | +36 |  14  |  1 daytime 
    26 Nov 2015 09:42 | 99- | 06:10 | -+8 |  11  |  9 large Moon 
    20 Jan 2016 02:29 | 83+ | 22:06 | -57  | 59  |  8                   
    10 Apr 2016 22:19 | 17+ | 18:22 |   0  | 43  |  3 twilight 
    04 Jun 2016 19:05 |  0- | 15:12 | +45  | 38  |  5  daytime 
    29 Jul 2016 11:09 | 23- | 05:37 |  +7  | 50  | 13 daytime 
    19 Oct 2016 06:33 | 86- | 01:15 | -53  | 60  |  8 
    13 Dec 2016 04:27 | 99+ | 23:50 | -73  | 64  |  4 large Moon 
    05 Mar 2017 02:57 | 47+ | 23:22 | -54  | 14  | 15 brief event 
    28 Apr 2017 17:33 |  7+ | 12:05 | +64  | 55  |  1 daytime 
    22 Jun 2017 14:36 |  4- | 09:23 | +53  | 62  |  5 daytime 
    12 Sep 2017 12:25 | 58- | 08:32 |++32  | 40  |  4 daytime 
    15 Oct 2017 11:24 | 20- | 05:14 | -11  | 39  |  9  
    06 Nov 2017 02:29 | 95- | 20:27 | -42 |  21  |  4 large Moon 
    31 Dec 2017 00:28 | 93+ | 18:48 | +24 |  43  |  11 large Moon 
    23 Feb 2018 17:12 | 54+ | 11:20 | +38 |   0  |   5 low alt 
    The columns are: 
    UT date and hour - The time when the occultation is greatest any 
where on Earth, which for sure is not in New York 
    %SL - sunligghted fraction of lunar disc. + for waxing; -, waning 
    EST - EST of mid event in New York City. Ignores EDST. Watch for 
an intervening midnight crossing between UT and EST. 
    Sun - altitude of Sun at mid event. + for Sun above horizon in 
daylight; -, under horizon in twilight or nighttime 
    star - altitude of Aldebaran at mid event, always above horizon 
    Sep' - separation in arcmin of Moon and Aldebaran at mid event 
    Altho we are favored with many Aldebaran occultations in this 
current  series, some are challenged by impediments. These are noted 
after the Sep' column. A few occultations have multiple impediments 
but only one of them is noted. Which of these events you may observe 
depends on your observing skills and tools and the instant sky 

    This occultation obeys the Rule-of-19. Given the date of any one 
instance, others occur at 19-year intervals on the same date. The 
series continues for several rounds before, like just about all other 
'cycles' in lunar motions, falls apart. The expired series is replaced 
by a new one. 
    The previous Rule-of-19 Aldebaran occultation took place on 25 
November 1996. The one day discrepancy is a calendar jiggle. New York 
missed it for happening after moonset. The Moon was full, 100% 
    The next Rule-of-19 event is on 2034 November 26 at 05:03, for mid 
event. We see this one almost a duplicate of the 2015 show with the 
 99% lighted Moon low in west.
    Mind well that the rule, like the similar Saros cycle, does not 
give the date of the very next or previous event! Between the three 
Aldebaran occultations of 1996, 2015, 2034 there are many others. Each 
follows its own Rule-of-19 cycle. 

    I missed the September 2015 event for low altitude. The Moon was 
behind skyline and trees. 
    I lost the daytime occultation in October 2015. I just could  not 
ever catch sight of Aldebaran in daylight against the Moon.  The sky 
was too hazy. 
    Now om Thanksgiving Day of 2015 I saw half of this occultation. I 
missed the reappearance of the star due to overly bright sky. 
    In spite of these duds, I'll be watching for the future 
occultations. Aldebaran occultations are of special meaning for me 
because the very first occultation I watched was of Aldebaran on July 
19th, 1960 in predawn hours. The Moon ws a waning crescent with 
Aldebaran ingress at the bright limb.. Yes, thank you, Thanksgiving!