C/2020 B3 (Rankin)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	21 Oct 2019	21.2	3.327 AU	3.976 AU	10h47m	-02°53'	43.6°	11.9°	282°
Nearest approach	13 Mar 2020	20.6	3.590 AU	2.615 AU	12h18m	-03°57'	166.9°	3.6°	301°
Today	4 Dec 2025	31.2	16.106 AU	16.950 AU	18h20m	-03°43'	30.2°	1.8°	50°

The interactive orbit chart above shows the comet's path through the solar system and its position at the given date. Green and blue lines are shown perpendicular to the ecliptic plane: Green if the path is above the ecliptic plane, blue if it is below. (Left-click and drag to rotate the view; Right-click and drag to move the view; Use scroll wheel to zoom in our out.)

Light curve

The light curve chart below shows the estimated development of the comet's magnitude. Blue and black dots are visual and photometric CCD observations from COBS. The light curve is based on the absolute magnitude and slope parameter as calculated from an MPEC, or the latest values provided by the minor planet center. (13.0 + 5 log[∆] + 10.0 log[r]). An additional green curve is displayed when an increase in apparent brightness is expected due to forward scattering of sunlight, which occurs when a dust-rich comet is located between the Earth and the Sun. (See Marcus 2007)

Charts

The all-sky chart below shows the path of the comet over the same period as the light curve. The comet's current position is marked yellow.

The following chart shows the short-term path of the comet in a field of view that is optimized for (~10x50) binoculars and finderscopes.

Orbital elements

The orbital elements of C/2020 B3 (Rankin) are:

    e (Eccentricity)                : 0.9969730
    q (Perihelion distance)         : 3.3269180
    i (Inclination)                 : 20.70680
    Ω (Longitude of ascending node) : 185.71840
    ω (Argument of perihelion)      : 324.95980
    L (Longitude of perihelion)     : 152.45536
    B (Latitude of perihelion)      : -11.71313
    T (Time of perihelion passage)  : 2458777.61530
    P (Orbital period in years)     : 36437.16

    Epoch                           : 2025 Nov 12
    Reference                       : MPEC 2022-N37

    Classification(s):              : Nearly isotropic; Returning (a < 10000 AU); External (P > 200 years)

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-12-03 00:00 UT   18 19 56.6   -03 42 37    16.935   16.099   31.1    1.8    52   31.2 
2025-12-04 00:00 UT   18 20 12.0   -03 42 56    16.947   16.105   30.4    1.8    50   31.2 
2025-12-04 06:27 UT   18 20 16.1   -03 43 00    16.950   16.106   30.2    1.8    50   31.2 
2025-12-05 00:00 UT   18 20 27.5   -03 43 13    16.958   16.110   29.6    1.7    49   31.2 
2025-12-06 00:00 UT   18 20 43.0   -03 43 29    16.970   16.115   29.0    1.7    48   31.2 
2025-12-07 00:00 UT   18 20 58.6   -03 43 45    16.981   16.121   28.3    1.7    46   31.2 
2025-12-08 00:00 UT   18 21 14.3   -03 43 58    16.992   16.126   27.6    1.6    45   31.2 
2025-12-09 00:00 UT   18 21 30.1   -03 44 11    17.003   16.131   27.0    1.6    43   31.2 
2025-12-10 00:00 UT   18 21 45.9   -03 44 22    17.013   16.137   26.3    1.6    42   31.2 
2025-12-11 00:00 UT   18 22 01.7   -03 44 32    17.023   16.142   25.7    1.5    40   31.2 
2025-12-12 00:00 UT   18 22 17.6   -03 44 41    17.033   16.148   25.1    1.5    38   31.2 
2025-12-13 00:00 UT   18 22 33.6   -03 44 49    17.043   16.153   24.5    1.5    37   31.2 
2025-12-14 00:00 UT   18 22 49.6   -03 44 55    17.052   16.158   24.0    1.4    35   31.2 

    Terminology:
            
    delta:  distance between comet and earth in AU
    radius: distance between comet and sun in AU
    magn:   magnitude (brightness) estimate    
    ra:     right ascension in hours (24h = 360deg)
    dec:    declination in degrees
    elong:  elongation in degrees (angle sun-earth-comet)    
    phase:  phase angle in degrees (angle sun-comet-earth)        
    AU:     Astronomical Unit (mean distance between earth and sun: 149597870.7 km      
    

Orbital elements usually provided by the MPC (Minor Planet Center).
Observations contributed by observers worldwide, via COBS (Comet Observation Database) or the MPC (Minor Planet Center)
Calculations by a modified version of AAPlus, a C# implementation of the AA+ project by PJ Naughter from the algorithms presented in the book "Astronomical Algorithms" by Jean Meeus.
NGC2000 dso catalog and star labels from VizieR as provided by the Strasbourg astronomical Data Center.
Tycho2 catalog from the ESO archive.