WILL REGULUS BLINK? ------------------ John Pazmino NYSkies Astronomy Inc www.nyskies.org firstname.lastname@example.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
To report your observations, stop at
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.