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Stellar Occultation of Regulus by Asteroid (2589) Daniel on 2021 Mar 09

Asteroid (2589) Daniel (16.9 mag) will occult 1.3 mag bright star Regulus on 2021 March 09.

Steve Preston‘s prediction below is based on data from JPL Horizons which was updated with latest observations of the asteroid made with the astrometric satellite Gaia.

Figure 1. The predicted path for Europe of the occultation of Regulus by (2589) Daniel made with data from JPL Horizons. Predicted by Steve Preston, IOTA, on 2021 March 05. Graphic made with Dave Herald’s Occult V4.

The Target Star

RA 10 08 21.9519 DEC +11 58 02.070 (astrometric)
RA 10 09 30       DEC +11 51 46 (of date)
Constellation: Leo
Vmag: 1.3
Apparent diameter: 1.4 mas

The Asteroid

(2589) Daniel
Diameter: 9.4 km +- 1 km
Apparent diameter: 6 mas
Geocentric distance at time of occultation: 2.14 AE

The Occultation

With an apparent diameter of 6 mas for the asteroid the target star will be occulted with a mag drop 15.6 mag inside the real path with a maximum duration of only 0.94 s. Observers should expect fades of > 0.2 s caused by the large diameter of the star (1.4 mas).

Stations at the limits of the real path should be prepared to record a grazing occultation by the asteroid. The mag drop in this case could be much fainter.

There is an uncertainty in star position due to the astrometric position for Regulus from the Hipparcos catalogue, corrected with proper motions. So observations inside the 1-sigma and 2-sigma limits are very important and highly recommended. A path shift should be expected.

Have a look at the table of path coordinates for the time of occultation at your location:

The Path – Worldwide Maps

The occultation begins in Malaysia. The shadow will cross Vietnam, Cambodia, Thailand and Myanmar:

The shadow will cross India, Parkistan, Afghanistan, Iran and north-east of Turkey:

After crossing the Black Sea the shadow will move on across Romania and Hungary:

The north-east of Austria will be inside path before the shadow crosses southern Germany, Luxembourg, southern Belgium and France just south of Calais:

Finally southern UK and southern Ireland are inside the path before the shadow will cross the Atlantic and the target star will be unobservable in the daylight:

Figures 2-7. The occultation will occur between the two red lines with a probability of 68 %. (Map data: 2021 Google, INEGI, (c) 2021 GeoBasis-DE/BKG ((c) 2009), Google, Inst. Geogr. National)

A path map of the occultation with zoom function is available on Derek C. Breit’s web page (IOTA):

Please choose the exposure time and gain of your camera carefully. A high frame rate and a good signal-to-noise ratio is necessary for the detection of any fades in brightness at the disappearance and reappearance of Regulus and for a grazing occultation as well.

Good luck with your observation,

Oliver Klös
Public Relations