C/2021 V1 (Rankin)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	31 Oct 2021	20.6	3.498 AU	2.718 AU	23h29m	+35°33'	135.8°	11.4°	108°
Perihelion	30 Apr 2022	20.8	3.020 AU	3.998 AU	02h23m	+02°48'	12.1°	4.0°	187°
Today	4 Dec 2025	28.7	10.942 AU	11.284 AU	11h26m	-44°19'	67.3°	4.8°	280°

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/2021 V1 (Rankin) are:

    e (Eccentricity)                : 0.9958320
    q (Perihelion distance)         : 3.0202620
    i (Inclination)                 : 71.42490
    Ω (Longitude of ascending node) : 207.71160
    ω (Argument of perihelion)      : 195.22670
    L (Longitude of perihelion)     : 212.66714
    B (Latitude of perihelion)      : -14.41581
    T (Time of perihelion passage)  : 2459700.07960
    P (Orbital period in years)     : 19506.32

    Epoch                           : 2025 Nov 12
    Reference                       : MPEC 2022-CN4

    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   11 26 08.6   -44 13 42    11.292   10.931   66.1    4.7   278   28.7 
2025-12-04 00:00 UT   11 26 17.4   -44 17 07    11.288   10.937   66.8    4.8   279   28.7 
2025-12-04 19:57 UT   11 26 24.3   -44 19 57    11.284   10.942   67.3    4.8   280   28.7 
2025-12-05 00:00 UT   11 26 25.7   -44 20 31    11.283   10.943   67.4    4.8   280   28.7 
2025-12-06 00:00 UT   11 26 33.6   -44 23 55    11.279   10.949   68.1    4.8   280   28.7 
2025-12-07 00:00 UT   11 26 41.1   -44 27 17    11.274   10.955   68.7    4.8   281   28.7 
2025-12-08 00:00 UT   11 26 48.1   -44 30 39    11.269   10.962   69.4    4.8   282   28.7 
2025-12-09 00:00 UT   11 26 54.7   -44 33 60    11.264   10.968   70.0    4.8   283   28.7 
2025-12-10 00:00 UT   11 27 00.8   -44 37 20    11.260   10.974   70.7    4.9   283   28.7 
2025-12-11 00:00 UT   11 27 06.4   -44 40 39    11.255   10.980   71.4    4.9   284   28.7 
2025-12-12 00:00 UT   11 27 11.6   -44 43 56    11.249   10.987   72.1    4.9   285   28.7 
2025-12-13 00:00 UT   11 27 16.3   -44 47 13    11.244   10.993   72.7    4.9   286   28.7 
2025-12-14 00:00 UT   11 27 20.5   -44 50 28    11.239   10.999   73.4    4.9   286   28.7 

    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.