P595.1 Occultation August 13, 2008

(last updated 2008 04 01)

The shaded dark grey area represents where the sun is more than 12 degrees below the horizon. The light grey region represents where the sun is between 12 degrees and 0 degress (sunrise) below the horizon. Across the globe pictured above, the three lines correspond to the northern limit, centerline, and southern limit of Pluto's shadow. The northern and southern limits correspond to a radius of 1208 km (the 50% normalized stellar-flux level) for Pluto.


Geocentric Mid-time (yyyy month dd hh:mm:ss) 2008 August 13 05:19:27± 00:03:45 UT
Minimum Geocentric Separation 0.310± 0.068 arcsec
Position Angle (Pluto relative to the star; measured north through east) –17.92 degrees
Geocentric Velocity 12.8 km/sec
Prediction Version P595.1-AST-1.0


Reference star position:
(USNO-B1.0, at epoch of event)
RA (h:m:s; J2000) Dec (d:m:s; J2000) R Mag1
P595.1 Catalog2 17 53 58.4787 –17 12 15.300 15.2
P595.1 Measured

1From USNO-B Catalog.

2USNO-B, at epoch 1971.5.

Offsets from Reference Position/Ephemeris3
Body RA (arcsec) Dec (arcsec) Notes


No star measurements at this moment

–0.0248± 0.019

+0.059± 0.019 See note 5

3All "offsets" are defined in the ("corrected" – "reference") or ("observed" – "calculated") sense. The offsets should be added to reference positions to get the measured positions, which we use to calculate the prediction.

4The reference position for Pluto is that given by JPL Horizon's ephemeris (Pluto source file: PLU017; Earth center source file: DE405).

5245 strip scans and 89 USNO-61inch Telescope frames were used to develop a model to fit the residuals obtained from our measured positions compared to that of the object's JPL ephemeris.. The model includes the first-order effects of errors in the orbital elements of Pluto: (i) constant offsets in RA and Dec, (ii) linear (in time) offsets in RA and Dec, (iii) sinusoidal terms with the Earth's orbital period, and (iv) sinusoidal terms with the Pluto-Charon mutual orbit.


Site Information

East Longitude







–155 28 29
19 49 46
2909 N.
center of Earth
7119 S.

7Altitude of each observatory is measured in kilometers above sea level.

8"Distance" refers to the closest approach distance of the "Site" to the center of Pluto's shadow in the shadow plane. The errors on all closest approach distances are ±1523 km (one standard deviation). "S." means the site is South of the center of Pluto's shadow. "N." means the site is North of the center of Pluto's shadow.

P595.1 Occultation Predictions for Individual Sites

Pluto Immersion (UT)9
Mid-Time (UT)9

Pluto Emersion (UT)9

Solar Elevation 10
05:20:42 (48°)

9The errors on all times are ±3:45 (3 minutes and 45 seconds; one standard deviation). In parenthesis is the elevation of the body above the celestial horizon in degrees.

10At the closest approch time for that location.

** Internal note: A– (20080401) **

Last updated by Carlos A Zuluaga (czuluaga@mit.edu) 2008-04-01 11:30

Please direct all inquiries to Planetary Astronomy Lab (planetary-astronomy@mit.edu)