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Old September 21st, 2019 #4
Jerry Abbott
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Join Date: Nov 2007
Location: In the hills north of Hillsboro WV
Posts: 1,048
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The astronomers are still fine-tuning the estimates of the orbital elements for C2019/Q4 Borisov. The most recently published set appear below. The determination for these elements involved 253 observations made over 21 days. The orbital elements are from JPL's Horizons webpage. The calculations are by me.

ORBITAL ELEMENTS
a = −0.8292162089229415 AU
e = 3.445224326645891
i = 43.86288391209771°
Ω = 308.3331498795959°
ω = 208.6433660112291°
T = 2458825.5456982227 JD

PERIHELION
time: 1h 5m 48s on 8 Dec 2019 UTC (JD 2458825.54570)
Borisov mean Anomaly: 0°
Borisov eccentric Anomaly: 0°
Borisov true Anomaly: 0°
HEC x = −1.65339477 AU
HEC y = +0.961210424 AU
HEC z = −0.673499574 AU
HEC Vx = −8777.78593 m/s
HEC Vy = −33890.4638 m/s
HEC Vz = −26819.2028 m/s
HEC distance: 2.02761965 AU
HEC longitude: 149.828179°
HEC latitude: −19.400094°
speed relative to the sun: 44100.8243 m/s = 0.000147104516 c
obliquity of the ecliptic: 23.4366993°
Geocentric distance: 2.01814923 AU = 16.7844354 light minutes
Geocentric right ascension: 11h 27m 03.85s
Geocentric declination: −17° 43′ 56.4"
Angle Sun-Earth-Borisov: 76.4422795°
Angle Earth-Sun-Borisov: 75.3737762°

CLOSEST APPROACH TO EARTH
time: 2h 48m on 28 December 2019 UTC (JD 2458845.617)
Borisov mean anomaly: 26.198589°
Borisov eccentric anomaly: 10.6281615°
Borisov true anomaly: 14.2156562°
HEC x = −1.74324442 AU
HEC y = +0.562480355 AU
HEC z = −0.978914843 AU
HEC Vx = −6730.66368 m/s
HEC Vy = −34811.9564 m/s
HEC Vz = −25825.2031 m/s
HEC distance: 2.07691106 AU
HEC longitude: 162.117033°
HEC latitude: −28.1208006°
speed relative to the sun: 43864.7382 m/s = 0.000146317017 c
obliquity of the ecliptic: 23.4366922°
Geocentric distance: 1.95820212 AU = 16.2858705 light minutes
Geocentric right ascension: 11h 58m 55.14s
Geocentric declination: −32° 53′ 45.1"
Angle Sun-Earth-Borisov: 82.7202806°
Angle Earth-Sun-Borisov: 69.2675344°

EPHEMERIS for December 2019
All positions for 9pm Eastern Standard Time
(date) (right ascension) (declination)
1 Dec 11h 17m 06.88s −13° 13' 15.4"
6 Dec 11h 25m 28.22s −16° 59' 59.2"
A meddlesome waxing moon
11 Dec 11h 33m 41.69s −20° 48' 55.2"
Full moon on 12 Dec.
16 Dec 11h 41m 46.08s −24° 38' 01.1"
21 Dec 11h 49m 39.93s −28° 25' 10.3"
26 Dec 11h 57m 21.45s −32° 08' 18.3"
31 Dec 12h 04m 48.51s −35° 45' 28.3"

Expected brightest apparent magnitude: +15.5
Borisov's hyperbolic excess speed: 32708.4 m/s

HEC : heliocentric ecliptic coordinates

Right ascension and declination are measured in geocentric celestial coordinates.

Angles are subtended by the object in the middle; the two objects on the ends are at the far end of the "rays." That is: Angle sun-Earth-Borisov is the angular distance between the sun and Borisov, to an observer on Earth.