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°	188°
Today	21 Oct 2025	28.6	10.667 AU	11.344 AU	11h14m	-41°52'	45.3°	3.8°	238°

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)         : 3.0201180
    i (Inclination)                 : 71.42690
    Ω (Longitude of ascending node) : 207.70920
    ω (Argument of perihelion)      : 195.22570
    L (Longitude of perihelion)     : 212.66389
    B (Latitude of perihelion)      : -14.41504
    T (Time of perihelion passage)  : 2459700.08960
    P (Orbital period in years)     : 19504.93

    Epoch                           : 2025 Oct 20
    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
2025-10-20 00:00 UT   11 13 17.0   -41 47 14    11.339   10.655   44.8    3.8   236   28.5 
2025-10-21 00:00 UT   11 13 41.5   -41 50 12    11.341   10.662   45.0    3.8   237   28.6 
2025-10-21 21:04 UT   11 14 02.8   -41 52 49    11.344   10.667   45.3    3.8   238   28.6 
2025-10-22 00:00 UT   11 14 05.7   -41 53 11    11.344   10.668   45.3    3.8   238   28.6 
2025-10-23 00:00 UT   11 14 29.7   -41 56 13    11.346   10.674   45.6    3.8   239   28.6 
2025-10-24 00:00 UT   11 14 53.5   -41 59 16    11.348   10.681   45.9    3.8   240   28.6 
2025-10-25 00:00 UT   11 15 16.9   -42 02 20    11.350   10.687   46.3    3.9   242   28.6 
2025-10-26 00:00 UT   11 15 40.1   -42 05 26    11.352   10.693   46.6    3.9   243   28.6 
2025-10-27 00:00 UT   11 16 02.9   -42 08 34    11.353   10.699   46.9    3.9   244   28.6 
2025-10-28 00:00 UT   11 16 25.5   -42 11 43    11.354   10.706   47.3    3.9   245   28.6 
2025-10-29 00:00 UT   11 16 47.8   -42 14 53    11.355   10.712   47.7    3.9   246   28.6 
2025-10-30 00:00 UT   11 17 09.8   -42 18 04    11.356   10.718   48.0    4.0   247   28.6 
2025-10-31 00:00 UT   11 17 31.5   -42 21 17    11.357   10.724   48.4    4.0   248   28.6 

    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.