Sedna.20121225; December 25, 2012

³Measured position corresponds to RA offset of +0.0218 and Dec. offset of –0.326.

⁴All "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.

⁴Data analyzed using UCAC2 reference network. A weighted average of the data from the two telescopes was used to calculate the RA and DEC. The errors given are 1 standard deviation.

⁵The reference positions for Haumea are those given by JPL Horizon's ephemeris (Sedna source file: JPL18; Earth center source file: DE405).

⁶Data from the USNO 61-inch, SMARTS 0.9m, and Lowell 42-inch telescopes over the span of 3 years were reduced with respect to stars in the UCAC2 catalog. A model was developed to fit the residuals obtained from our measured positions compared to that of the object's JPL ephemeris. All residuals obtained from the different telescopes were consistent with the model. The model includes the first-order effects of errors in the orbital elements of Quaoar: (i) constant offsets in RA and Dec, (ii) linear (in time) offsets in RA and Dec, and (iii) sinusoidal terms with the Earth's orbital period. The model was propagated to obtain the predicted position and error of the KBO at the time of the occultation. The errors listed for the KBO are 1 standard deviation.

Table 1: Prediction Details
Sedna Geocentric Mid-time (yyyy month dd hh:mm:ss)	2012 December 25 03:32:51± 00:03:14¹ UT
Sedna Minimum Geocentric Separation	0.072± 0.056¹ arcsec
Position Angle (Sedna relative to the star; measured north through east)	–1.62 degrees
Geocentric Velocity	19.18 km/sec
Occultation Star USNOB R magnitude	18.71²

Table 2: Reference Star Position
Reference star position: (UCAC2, at epoch of event)	RA (h:m:s; J2000)	Dec (d:m:s; J2000)	Notes
Sedna.20121225 Catalog	03 33 12.9280 ± 0.1530	+06 46 51.140 ± 0.071
Sedna.20121225 Measured³	03 33 12.9295 ± 0.0120	+06 46 50.814 ± 0.005	From 3 USNO 61-inch frames
Table 3: Projected KBO Offsets from Reference Ephemeris at the Time of the Event
Body	RA (arcsec)	Dec (arcsec)
Sedna	0.0613 ± 0.0595	–0.037 ± 0.056	See Notes 5 and 6
³Measured position corresponds to RA offset of +0.0218 and Dec. offset of –0.326. ⁴All "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. ⁴Data analyzed using UCAC2 reference network. A weighted average of the data from the two telescopes was used to calculate the RA and DEC. The errors given are 1 standard deviation. ⁵The reference positions for Haumea are those given by JPL Horizon's ephemeris (Sedna source file: JPL18; Earth center source file: DE405). ⁶Data from the USNO 61-inch, SMARTS 0.9m, and Lowell 42-inch telescopes over the span of 3 years were reduced with respect to stars in the UCAC2 catalog. A model was developed to fit the residuals obtained from our measured positions compared to that of the object's JPL ephemeris. All residuals obtained from the different telescopes were consistent with the model. The model includes the first-order effects of errors in the orbital elements of Quaoar: (i) constant offsets in RA and Dec, (ii) linear (in time) offsets in RA and Dec, and (iii) sinusoidal terms with the Earth's orbital period. The model was propagated to obtain the predicted position and error of the KBO at the time of the occultation. The errors listed for the KBO are 1 standard deviation.

Site	KBO Immersion (UT)⁹	UT Mid-Time	KBO Altitude	Solar Altitude⁹	KBO Emersion (UT)⁹
Wallace	03:30:50	03:31:15	-----------	-----------	03:31:39
Geocenter	-----------	03:32:51	-----------	-----------	-----------

Sedna.20121225 Occultation December 25, 2012