WILL REGULUS BLINK?
------------------
John Pazmino
NYSkies Astronomy Inc
www.nyskies.org
nyskies@nyskies.org
2014 February 14
Introduction
----------
One of the very rarest of astronomy events favors New York City in
owl hours of 2014 March 20 Thursday. Asteroid #163, Erigone, passes in
front of star Regulus and obstructs its light from reaching us!!
Occultations like this are common from the immense number of
asteroids and of stars in their path, about a half million of each.
The covering of a bright star, specially one readily spotted by the
public with bare eye, by an asteroid over a given location is, uh,
excedingly rare. It is litterally a once-in-liftime show.
Unlike an eclipse or occultation with the Moon, you have no
anticipation of the cutoff of Regulus. You can not in small scopes see
Erigone. At the moment of totality Regulus suddenly blinks out as if
its power switch was flipped to 'off'. After a few seconds it turns
back on again. And that's it.
I customized this article for astronomers in the NYSkies
territory, out to 100 kilometers from Times Square, plus all of Long
Island. Readers beyond this region must obtain locality-adjusted
information for their own districts.
This piece incorporates substantial material from International
Occultation Timing association and its staff. Special thanks go to Ted
Blank and Steve Preston for providing much of the information here and
a review of a draft version of this article.
Regulus
-----
There is abundant litterature about this star reaching back to the
earliest times of recorded astronomy some five and more thousand years
ago. Regulus was always a cardinal star along the ecliptic, watched
and monitored by virtually all cultures cognizant of the planetary
motions. In about 2200 BC Regulus marked the summer solstice point.
I give here only a few considerations for it. One fascinating fact
is that Regulus is not a sphere. It rotates rapidly to squish its
photosphere into a oblate spheroid! Altho here to fore this shape is
studied by interferometry, this occultation MAY reveal it from
processing your observations. This is no promise but is COULD result
that the recorded behavior of Regulus is best explained by a
ellipsoidal, not circular, disc.
Some specifications of Regulus are given here. Please be aware
that because these data came from diverse sources, certain items may
be discordant against each other.
-------------------------------------------
designations
------------
Proper name Regulus; Cor Leonis; Al Kalb al Asad; Kabeleced
Bayer letter alpha Leonis
Flamsteed number 32 Leonis
Yale Bright Star HR 3982
Tycho TYC 833-1381-1
Pos Pro Mot PPM 127140
Henry Draper HD 87901
Zodiacal ZC 1487
Fund'l Katalog 5 FK5 380
Smithsonian SAO 98967
New Susp Var NSV 04751
Hipparcos HIP 49669
Bonner Durch'g BD +12:2149
---------
atlas charts
------------
Herald-Bobroff chart C-49
Millennium Atlas chart 731-732 (Vol II)
Sky Atlas 2000.0 chart 13
Uranometria 2000 chart 189 (Vol 1)
----------------
coordinates (J2000.0)
---------------------
Right Ascension 10h 08m 22.3127s
Declination +11d 58m 01.955s
Ecliptic long 160d 1.5m
Ecliptic lat +0d 27.9m
Galactic long 226d 25.6m
Galactic lat +48d 56.0m
------------
distance & motion
-----------------
Distance 76.9 ly, 23.6 pc
Trig parallax 0.04240 arcsec
Prop motion RA -0.25218 arcsec/yr
Prop motion DE +0.00660 arcsec/yr
Radial velocity +10.2 km/s
--------------
Radiation
---------
Visual magnitude +1.41
Mean B magnitude +1.360
Mean V magnitude +1.399
Max V magnitude +1.35 susp var
Min V magnitude +1.47 susp var
Johnson B-V -0.036
Abs magnitude -0.52
Luminosity 123 Sun
----------
Physical
--------
Spectral class B7 V
Temperature 10700 kelvin
Radius 4.1 Sun
Mass 3.8 Sun
Duplicity Quadruple star
Shape oblate spheroid
---------
New York City
-------------
Rise azimuth +73d 42m
Culmination alt +61d 18m
Set azimuth +286d 18m
Diurnal arc 13h 32m
-----------
Erigone
-----
The name is Greek, 'eh-RIH-go-nee'. Don't say 'EH-rih-gohn'.
Erigone is a larger asteroid, some 70 kilometer diameter, but of
uncertain shape. The data here come from various sources and seem to
be about as good as any others to hand.
-------------------------------
History
-------
DiscoverY year 1876
Asteroid number 163
Proper name Erigone
-----------
Physical
--------
Linear diameter 72 km
Category C-carboneceous
Albedo 0.04
Absolute magnitude H +9.41
Magnitude slope G -0.04
--------------------
Observation record
------------------
Date of fit 2014 Jan 19
Number of good obsns 1288
Number of rejects 98
Timespan of obsns 1903 Sep 23 - 2014 Jan 18
-----------------
Orbit elements
--------------
Epoch of elements 2456736.255 TDT, 2014 Mar 20.255
Mean anomaly at epoch 46.28782507 deg
Arg of perihelion 298.23787787 deg
Long of asc node 160.17363738 deg
Inclination 4.81452364 deg
Eccentricity 0.19116015
Semimajor axis 2.36690097 AU
Perihelion dist 1.91444383 AU
---------------
New York City
-------------
Angular diameter 0.084 arcsec
Distance from Earth 1.185 AU
Visual magnitude +12.4
Duration of totality 14 sec, probable maximum
Projected path width 108 km
Totality hour & date 02:05 EDST Thu 20 Mar 2014
Uncertainty of hour 3.9 sec
Shadow speed WRT Earth 5.09 km/s
Regulus position 44 deg alt, 243 deg azm
Moon aspect 87% sunlighted, 71d E of Regulus
Sun aspect full night
---------------
Ground path
----------
The ground track of the occultation in the vicinity of New York is
given here. The path is about 100 kilometers wide, centered on the
ground track. In the NYSkies territory the asteroid enters from
southeast, passes right thru New York City, and leaves to northwest.
The favored locations within NYSkies are Tappan Zee and Mid
Hudson, Catskills, Taconics, southwest Connecticut, north New Jersey.
most of Long Island (missing the east ends of the Forks), most of New
York City (missing Staten Island), The west and south sectors of
NYSkies are off of the west edge of the shadow oath.
Observing from beyond this zone is absolutely needed and can
produce valuable information on the lateral limits of Erigone's size.
Please stand watch for this occultation REGARDLESS of your location!!
A negative observation is as worthy as a positive one.
There is an uncertainty of up to 4 seconds in time along the path
and of several kilometers to either side of the path. This combines
the unknown topography and shape of Erigone and displacement from its
predicted motion. An other error source is the astrometry of Regulus.
------------------------------------------------------------------
Center line--------- UT hour-- Star---- Sun
W Long Latitude March 20 Alt Azim Alt
--------- ---------- --------- --- ---- ----
72d27m43s +39d39m38s 06h05m47s 42d 247d -48d
73 14 06 +40 30 03 06 06 09 42 246 -47
74 00 08 +41 20 41 06 06 30 42 245 -47
74 45 53 +42 11 33 06 06 52 42 243 -46
75 31 23 +43 02 41 06 07 13 42 242 -45
-------------------------------------------
Mind very well that the occultation occurs under Eastern Daylight
Savings Time, FOUR hours behind Universal Time. For the City the star
blinks out at 02:06 EDST and NOT 02:06 EST.
You may plot the center line on a topographic map to see what you
may expect from your location. For other lat-lon within the range
given here linear interpolation is adequate.
The closer you are to the edge of the path, 50 kilometers parallel
to the center line, the shorter is totality and greater is the chance
of a complete miss.
Possible satellites
-----------------
Erigone has no known moons. Since moons are already known around
even smaller asteroids, it's possible that observers beyond the
central path will see Regulus shut off ever so briefly due to an
outlying moon. This is a stretch of hope, yet sometimes major new
astronomy springs from accidental discovery.
This means that the zone of POSSIBLE blinking of Regulus is NOT
just in the shadow path, but for about 700 kilometers adjacent to it
on both sides. This zone within the US covers the eastern Great Lakes,
Ohio Valley, Appalachia, Mid Atlantic, Chesapeake Bay, New England.
A satellite may be ahead or behind Erigone, in a zone again 700
kilometers wide. With a nominal speed of the asteroid's shadow on the
ground of 5 KPS, a satellite COULD touch Regulus as long as 150
seconds before or after the asteroid itself does. Or, EEeek!, Erigone
misses Regulus but a moon of it hits the star. You may want to stand
watch a couple minutes early and keep it thru a couple minutes after
the totality hour.
A shutoff of Regulus by a moon is very brief, less than a second.
For this reason, the blink COULD come from a local terrestrial action,
like by a bird or lofted rubbish. To confirm a blink by an Erigone
satellite we need at least TWO consistent observed events along the
same axial line.
I stress there are NO predictions for events by satellites of
Erigone. It could easily turn out that NO moons are detected from this
occultation.
Possible companions
-----------------
In this century we found so far three companions of Regulus. One
is a close-in comes making a binary star with Regulus. The other two
are a second binary star in a distant orbit around Regulus. This star
is the here to fore assumed line-of-sight companion that is commonly
mentioned in observing guides.
For all feasible observing methods for home astronomers the
occultation will not produce any evidence of the inner component. The
outer pair casts its shadow well off of Earth. Perhaps an observatory
with high-speed, high-resolution, photometry may find the close
companion against Regulus. This is very iffy.
Finding Regulus
-------------
For newcomers to the sky it can be difficult to confidently point
to a star and correctly identify it. I'm not joking. IF you watch the
wrong star, thru ignorance or mistake, you will LOSE THIS OCCULTATION
with essentially no further opportunity for a second chance for the
rest of your life!!
Get familiar with Regulus NOW, long before the occultation! It's
in high sky in east and southeast at nightfall in March. Once found,
you can follow it thru the night to the occultation.
Most starID litterature tells you to find the 'Sickle' asterism
forming the head of the Leo constellation, of which Regulus is the
heart. In a sky with strong haze, moonlight, luminous graffiti the
Sickle is obscured. Its other stars are weaker than Regulus.
Exercise your planetarium software. Start at a known group like
the Big Dipper or Orion. Walk from them toward Regulus, making sure
you match wayside stars with the software display. You may also use a
mechanical device, like a planisphere, but be wary of its distorted
map projection.
For this event, Regulus is on the line from Jupiter thru the
Beehive cluster as as far beyond. It is also quite half between
Jupiter and Mars. ti is roughly an equilateral triangle with Alphard
and Caput Hydrae. It's a full Dipper's length south of the Big Dipper
at the south end of the Sickle asterism.
For aiming a camera at Regulus, the star is too dim to show up in
the finder screen. Carefully note above which landmark in the
landscape Regulus stands and aim with that feature near the bottom of
the screen.
Once getting Regulus in the camera field you may zoom in or change
to a tele lens. Keep the field of view at least one degrees wide. This
allows Regulus to drift diurnnlly for a few minutes before and after
the occultation. At the time of the event Regulus is drifting from
upper left to lower right in the sky.
As far as I know digital cameras don't have changeable finders and
screens, like for chemocameras. With the older cameras astronomers
could aim and focus their celestial targets on a bright clear scene.
Please check your camera operations! Some cameras notch to some
close focal distance if there is no obvious target to fix on! You
could be foiled by Regulus being so strongly defocused that it diluted
out of sight. You may have to manually set the focus to infinity.
Bear in mind that even if the sky is hazy with few other stars in
sight, you will see the occultation. As long as Regulus presents a
definite firm image, you'll see it turn off and then turn on as well
as if it was shining in a pristine sky.
New York sky
----------
During the occultation Regulus is half up in southwest. Orion is
gone below the west. The east half of the Winter Hexagon, or Super
Bowl Football, arcs across the west. Virgo with Mars is culminating.
From Mars the zodiac slants to the southeast thru Moon, Saturn,
and Caput Scorpii. Vega is about 1/4 up in northeast. The Big Dipper
is in high north.
. To be sure your viewing spot has a clear sightline to Regulus,
simulate the sky with planetarium software and measurements of
potential obstructions at the site. Don't be killed by a surprise
blockage of view because you didn't do your homework. If nothing else
works, physicly look at Regulus at 02h EDST from your spot on days
before the occultation.
The Moon is a waning gibbous that may wash out fainter stars but
will pose no threat to Regulus. A haze or thin cloud could scatter
excessive moonlight and dull Regulus.
The bright Moon will oblitterate two weak meteor showers active
during the occultation. These are the beta Leonids and zeta Leonids.
They have only a couple meteors per hour under ideal conditions.
The occultation is an extra point of data for the GLOBE at Night
exercise. Orion, the target for GLOBE at Night, already set.
You may assess the sky by stars in Leo. Regulus is magnitude 1.
Denebola and Algieba are magnitude 2. Chort and Zosma are magnitude 3.
The rest of the Sickle asterism is magnitude 4. Stars in Leo Minor and
Sextans are magnitude 5. Include a note about the extent of lunar
interference for this measurement.
Please do the GLOBE at Night inspection of Regulus WHILE IT IS IN
FULL SHINE!!. Saying the sky was too bright to see Regulus when in
fact the asteroid was sitting on top of it will earn you the laughter
of the century.
Because of the Moon you probably will not get much deep sky
observing. Nor will you see any but the brightest of aurorae, if any
occur. If you're staying under the sky for a while, shift to observing
double stars, Mars, Saturn, and learning star-ID.
Here's a timetable for the night of 2014 March 19-20, Wednesday-
Thursday, for this show. All hours are Eastern Daylight Savings Time.
--------------------------------
EDST | event | remarks
------+---------------------+--------
19:07 | Sun sets | azimuth 91 deg
19:34 | civil twilight | end of daytime work
20:06 | nautical twilight | start of full night in NYC
22:24 | Moon rises | azimuth 109 dwg
23:14 | Regulus on meridian | altitude 61 deg
00:00 | midnight | March 19 --> March 20
02:06 | Erigone-Regulus occ | alt 44 deg, azm 243 deg
03:46 | Moon on meridian | altitude 34 deg
05:58 | Regulus sets | azimuth 286 deg
06:00 | nautical twilight | end of full night in NYC
06:32 | civil twilight | start of daytime work
06:59 | Sun rises | azimuth 271 deg
---------------------------------------
Date and hour
----------
It's astounding how even seasoned astronomers can louse up the
date of an event occurring in the midnight to dawn span. You must be
specially careful for the crossover at midnight into the next calendar
date. Missing that crossover puts you a full day out of step.
Already I'm seeing some sloppy advice to set up in the late night
of March TWENTIETH. This level of mistake slides you a whole day too
late. You're under Regulus at 02h EDST on the TWENTY-FIRST.
You do supper and a nap after sunset of March 19th. See the
occultation a few hours later on March 20th. Greet the rising Sun
later on the 20th.
The occultation occurs after the annual idiotic shift into Eastern
Daylight Savings Time! The crossover is on Sunday 9 March. EST is FIVE
hours behind UT; EDST, FOUR.
If you set up for 2AM EST, because you compiled plans before EDST
starts, you miss the occultation by a full hour. You were out there at
3AM EDST. Regulus for the rest of your life shines on and on.
Viewing location
--------------
View this occultation from any convenient location. Regulus is in
high sky, clearing most city skyline. You may use your normal
stargazing site if you want. It isn't necessary because Regulus is
accessible from all parts of the City. It is crucial that observers be
dispersed over the whole width of the shadow path and even beyond it.
While it is almost irresistible to seek the center line of the
path for the longest totality, like for a solar eclipse, this is
really NOT what is wanted in this situation. The profile of Erigone
could be such that the longest totality is OFF of the center line! One
purpose of viewing this occultation is to map out the shape and size
of the asteroid by collecting timings from its whole diameter.
This is why the best location could very well be your own home or
a nearby spot, NOT a remote stargazing site. Apart from simplifying
your observing plans, skipping most of the travel hassles, you enhance
the value of your observation by getting a measure of the asteroid
along a new and unique path.
Mind well that the event occurs at about 02h EDST, when many
plausible sites are closed or off limits.
If you plan to travel to a site, be VERY AWARE of rail and road
disruptions in owl hours. These hours are favored for massive work on
substantial segments of road and rail thruout the NYSkies region.
Several astronomy clubs are arranging for in-house observing of
the occultation for their members. They may use a site that's normally
closed to the public but is open by arrangement with the club.
Most will be happy to accommodate you, as a serious observer. If
you obtain invite to join observers, you take part as an observer! Do
NOT behave like at a public stargazing meet. Keep quiet, leave other
astronomers alone, maintain polite deportment.
NYC Events does not list internal events. You should inquire via
the contact for the club's listed public events.
Public viewing
------------
There probably will be few public viewing for this event. The owl
hour and instantaneous action of Regulus work against such a viewing.
Assume you will view this occultation on your own, whether by yourself
or with other convenient astronomers.
In the NYSkies region there are many observatories, typicly at
colleges and universities. Some may be cranked up to record the
occultation. It is not feasible for a public audience to watch Regulus
thru the telescope due to the limited facilities for such groups and
the excedingly brief totality.
It COULD be possible that an observatory can pipe images of the
star, maybe with the asteroid, to a lecture room. There the images are
showed on screen with live narration by observatory crew. As at issue
date of this article I have no news of any such show. Do ask at the
local observatory for its plans.
Geographic position
-----------------
As an astronomer you should already know the geographic position
of your observing site. Nowawyears this is taken from GPS receivers
and recorded somewhere in your observing kit. Besides a dedicated GPS
receiver, your smartpphone may allow a position readout from its
onboard GPS circuit.
You may still use the older technique of scaling off of USGS
toposheets, county survey maps, military cadasters, and the li. Other
sources for precise coordinates are the Internet mapping webs or GIS
software.
Mark your location within the displayed landscape, zoom in to get
a better fix. Do this for each plausible location you are considering
for viewing this occultation.
You need the coordinates to the 1/4 arcsecond in each axis because
the asteroid's relief is in the order of a tens of meters. 1/4
arcsecond is, uh, 7 to 8 meters on the ground.
Instrument
--------
You need a stably mounted telescope. Just about any scope is good,
so long as it has a sturdy steady stand, produces a solid clean image
of Rwgulus, follows the star easily. This may be by motor drive or by
smooth hand controls.
There is no need or desire to get hold of a large or powerful
telescope. Regulus is a bright star and Erigone can't be seen in any
scope you're likely to find to hand. You're watching for the total cut
off of Regulus as Erigone crosses over it. There is no detail or
structure to see, like for a lunar occultation or eclipse.
Magnify Regulus as high as possible while still keeping it a solid
image. If there is little moonlight, luminous graffiti, haze, you may
spot the remote companion star of Regulus. It's 8th magnitude, 3
arcminutes to the northwest.
Your hands, eyes, mind, body must be relaxed and free of stress.
Sit down, on a chair or stool or sturdy box. at the telescope. Turn
the eyepiece at a comfortable angle and height toward the eye.
Keep stray lights off of your face with shields of cardboard or
other opaque stiff material. A hooded jacket is helpful but the hood
could hinder you if you must handle equipment away from the eyepiece
like a audio recorder or computer.
Remove potential distractions like phone calls and interference
from pets. Let the rest of your household know you need calm and quiet
with no loud noise or annoying questions..
Eat well an hour or so before setting up for the occultation. Get
good sleep, at least a nap. Stay off of stimulants, even coffee. If
you normally use medical eyedrops, apply them before the observation.
Powerful trick
------------
THere's a trick sometimes used for lunar occultations of bright
stars. DELIBERATELY defocus the telescope to make Regulus a small
disc. Its face will be irregularly lighted due to atmospheric
scintillation.
This disc may be more confidently watched than a sharp point. When
Erigone touches it, the entire disc blinks out at once, with no fading
or dimming. After totality the disc of Regulus suddenly comes back
into view. This trick helps to distinguish momentary dimming from
twinkling from the real cut off of starlight by the asteroid.
There is the prospect of seeing with the defocused disc the
kinetics of Erigone moving across Regulus. The disc may not blink out
all at once but very rapidly, as if a door or lid was slammed over it.
This is speculative, yes, but it's something to be mindful of.
Eyesight
------
Most astronomers can cope with defective vision for telescopy. Low
vision folk who miss the fainter stars in the sky by bare eye usually
achieve full resolution and amplification with the telescope.
Two main factors can impede an observer for the occultation are
floaters and dead spots. Floaters are bits of eyeball lining that
somehow broke loose and are trapped in the liquid filling of the
eyeball. They show up as 'amoebae' drifting thru the visual field. In
daylight they are mostly innocent nuisances but at night they can be a
disaster for this occultation.
By swooshing the eye left-right the floaters are agitated and can
scoot past Regulus in the eyepiece field quickly enough to avoid
masking the star's shutoff. Trying to hold the eye still lets the
floaters settle at the bottom of the eyeball, seen as drifting to the
top in the visual field. This is a tough tactic since you WILL jiggle
the eye as a breeze hits it, a tear starts to drip, other distraction.
The other factor is a dead spot on the retina. In daylight you
probably never notice it because the eye-mind vision mechanism 'fills
in' the missing detail and the eye is in constant movement to take in
the landscape. At the telescope the effect is to blink out stars in a
certain area of the eyepiece field. Jiggling the eye restores the
stars but the dead zone remains fixed in the field. Be wisely of this
situation in your vision, perhaps from prior observing experience. Put
Regulus in a quarter of the field away from possible interference from
the dead spot.
One other defect that should be considered is astigmatism. Regulus
will focus to a small, but finite, dot. A bit of defocus renders it
into a short line. This image when hit by Erigone will snap out of
sight, then snap back into view, all at once
Weather
-----
This occultation is remarkably resilient against adverse weather!
As long as there are no thick or varying clouds, you'll see Regulus.
Even haze or thin cloud is no barrier.
Clouds scudding along, intermittently blocking view of Regulus,
are a severe hazard, as are clouds of variable density. The star
shines thru the thinner parts but is hidden behind the thicker parts.
One clue to catching the correct shutoff is that Regulus will turn
off instantly with no gradation of brightness. Same for the return to
normal brilliance many seconds later. Covering by mist, cloud, haze is
always gradual, with obvious dimming and swelling of light.
The air in owl hours of late March can be chilly. Wear a winter
coat. Have gloves and hat to hand in case the air gets too cold.
Prepare for moisture, specially if the night is within a spell of
rain. Dew can also form on optics and electronics if there's a steep
temperature drop from day to night. Have a dew zapper or small hair
drier handy
If you use ANY electric or electronic device, you WILL be
threatened by malfunction at the critical moment! March chill and
moisture can upend the works unexpectedly. Be ready and willing to
fall back to a simpler manual observing method.
Did Regulus blink?
-----------------
For readers with only a simple telescope there is creditable work
you can do. Diligently watch Regulus over a few minutes spanning the
occultation hour. Note carefully whether Regulus ever did blink out,
even if briefly, or it shined continuously with no interruption.
This observation bounds the maximum lateral dimension of the
asteroid. You may add a qualitative description of the duration of
blinkout.
In theory, and this is touted by some authors, you can watch by
bare eye. This is a VERY risky attempt. There will always be continual
and often random annoyances around you to momentarily divert your
attention. You will also be interdicted by the vision factors such as
those discussed in 'Eyesight'.
A severe impediment to a confident observation by bare eye is
twinkling. In strong wind Regulus may scintillate to send u false
alarms. You can easily miss the true occultation and record a long
twinkle.
This event is NOT like watching an aurora or meteor shower. You
must keep close attention on Regulus with no interruption of any kind
This discipline is almost impossible to enforce by merely standing
outside and looking up. Sitting can improve your work but not enough
for confident observation. Use at the very worse a tabletop telescope
on a stable stand.
This is a fetching example of a celestial event seemingly beyond
newer home astronomers to appreciate. It turns out to be among the
very easiest to experience, and make useful worthy observations.
Counting cigarets
---------------
An elaboration of the 'did it blink?' effort is to start counting
'cigarets' instantly Regulus shuts off. The time to say 'one cigaret'
swiftly but distinctly is quite one full second. The four syllables
are each quite 1/4 second. To maintain au even cadence, say 'sevv' for
'seven'. Restart the count for each round of ten seconds. Tally the
rounds of ten on a notepad.
We believe the shutoff will last a dozen or so seconds at the
most. Please be prepared in case we got the axial dimension of Erigone
wrong. Catch when Regulus appears again. Note the syllable just
COMPLETED when the star came back and the associated number word.
You'll be startled when Regulus turns off and suffer a split-
second delay in beginning the count. You will again be surprised when
Regulus pops back into sight. The delays at both ends more or less
cancel out.
This same reasoning applies to other timing methods where you must
manually act at both ends of totality. like pressing a stopwatch
button or tapping a timing software icon.
The number word STARTS the second. The second for that word ends
when the syllable '-ret' is sounded. The madeup timing below tells you
that totality lasted about 3-3/4 seconds
'one-ci-ga-ret, two-ci-ga-ret, three-ci-ga-ret, four-ci-ga- --'
|---second #1---|---second #2---|---second #3---|-incomplete sec #4
The very last syllable 'ret' was sounded after Regulus reappeared.
Eye and hand
------------
The next level is to time the duration of the shutoff with a
stopwatchor, The length of occultation is likely to be only a few
seconds. Yoy must be ready and quick to start the watch soonest
Regulus turns off and to stop it sonnest Regulus turns back on.
Most cellphones have a stopwatch function. The display is either
the duration, or two absolute times. For the latter case only the
difference of the times, the duration, is valid. Phone companies are
seeming lazy about synching their absolute times to the global timing
service.
The record gives the axial dimension of Erigone as it flies over
your location. Altho you have no absolute start and end hour, the
length of the 'off' phase can correlate and check other observations
along the same axis.
You may run an audio recorder while you speak the start and end of
the covering, along with an overlay of shortwave radio time signals.
By playing the recording you can measure the time of events against
the time signals. Use a crisp words, like 'off' and 'on', not, as
example, 'saw' and 'see'. The latter have a prolonged initial sound
that last several tenths of a second.
Timing software
-------------
An other method is to play a computer timing program that collects
times by pressing a button or icon. The advantage is that the timing
is recorded by the program to be retrieved later. The simpler ones
mimic a stopwatch, to the level of displaying a dial on the screen.
The fancier softwares also capture the absolute time of the event,
not just a relative one, by riding an external time service.
Here is a warning about the hour shown by a cellphone. Altho it
is issued by a precise circuit in the device it could be out of synch
against global time services.
Be sure your software actually rides the world atomic clock
services and not just that in the device. The discrepancy can be a
couple seconds! The phone company isn't all that diligent about
keeping in synch with the global time network. It may synch once a day
and let its time signals wander else when.
Some softwares allow you to send via email the recorded timings
directly to IOTA or other occultation center, In such models you first
fill in some personalia and specs of the event.
As at this article's issue date software suitable for this event
play on iPhone and Android devices.
Videography
---------
Tou may videograph the event and use the frame count as the timing
mechanism. Timing only the duration can be done with a stand-alone
video device. One such is a digital camera that stamps a count on each
frame. Setting this device on a tripod aimed at Regulus with a tele or
zoom lens should give frames that show the star, then many with no
star, and then the rest with the star again. The duration comes from
the sequence stamps on the frames with no Regulus in them.
The frame rate gives the duration of the blinkout. If, made up,
fifty frames capture Regulus in the shut off phase and the camera is
shooting 24 frames per second, the duration is
(duration) = (number of frames) / (frame rate)
= (50 frames) / (24 frames/second)
= (2.083 seconds)
-> 2.1 seconds
You can imprint an absolute time with the video by first shooting
Regulus and then WHILE LEAVING THE CAMERA RUNNING aim at a display of
absolute time on your computer. Let this display impress for a couple
seconds, THEN turn off the camera. The frame count from a time mark at
the end of the video back to one of the contact events gives the hour
of each event. The maths are like that shown above.
The time display may be out of focus because you were shooting at
infinity on Regulus and then aiming at a target close to you. As long
as the digits in the display are legible, if blurred, you got the
absolute time. You may place the time display a dozen or more meters
away to lessen the out-of-focus problem.
Improve the chances of getting Regulus to impress an image by
setting the 'film' speed, the ISO or ASA rating, to a high level. The
picture will be filled with static, like the 'snow' on analog
televisions. Regulus will be the only enduring image, covering many
pixels. When it is hidden by Erigone, ALL of its pixels go dark at
once. ALL come back on when Erigone leaves the star. That's the
fundamental observation, regardless of how awful the image looks.
Computer caution
--------------
You may be tempted to simulate this event with a planetarium
program. If Erigone is already in the database of orbits, it is for
sure totally ediurnate. Asteroid orbits go out of date after a few
years. Running simulations with ediurnate data yields wrong results.
You MUST get current orbit elements! These come from the Minor
Planet Center or JPL Small Solar System Body database. The elements
presented under 'Erigone' are valid as at late January 2014 and are
probably as good as you'll get then after.
Carefully key in the numbers into your planetarium. How you do
this is peculiar to each planetarium software. Study and exercise its
instructions!
You will NOT see Regulus blink out in the simulation. All
planetaria I ever saw treat asteroids as dead points. The best you can
expect is to watch the asteroid's dot touch and merge into Regulus,
then glide away on the other side. The star shines during totality.
News and information
------------------
As astronomers gear up for the event there will be a chatter
thruout Internet. One good starting place for general news, including
latest predictions, is International Occultation Timing Association,
IOTA, at
www.occultations.org/Regulus2014
To report your observations, stop at
www.occultwatcher.net/regulus-erigone
Conclusion
--------
This excedingly rare instance of an asteroid covering a bright
bare-eye star for us in the NYSkies land should not be passed up! What
may at first seem an impossible observing event is actually among the
very easiest of all celestial activity to appreciate with simple
instruments. And it requires no special place to view from.
There likely will be no future occasion for the City within this
generation for so bright a star to blink out of sight because a city-
size rock blocks its light. As long as there are no severe clouds, we
have a good chance to realize this experience.
Weather in March is usually mild, altho a lingering winter chill
can prevail. But that's easily handled with ordinary outer garments
and comforts. Only thick or roving clouds, and rain or a late snow,
will derail your effort.