C/2020 U3 (Rankin)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	18 Oct 2020	20.5	2.592 AU	1.870 AU	22h08m	+36°14'	126.7°	17.9°	106°
Perihelion	6 Feb 2021	20.5	2.286 AU	2.432 AU	00h54m	+30°47'	69.7°	23.9°	56°
Today	2 Jul 2025	31.7	12.824 AU	13.057 AU	10h44m	-23°13'	74.5°	4.4°	124°

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.)

The orbital elements of C/2020 U3 (Rankin) are:

            e (Eccentricity)                : 0.9662200
            q (Perihelion distance)         : 2.2856420
            i (Inclination)                 : 30.13880
            Ω (Longitude of ascending node) : 282.60040
            ω (Argument of perihelion)      : 124.51470
            L (Longitude of perihelion)     : 231.09052
            B (Latitude of perihelion)      : 24.43860
            T (Time of perihelion passage)  : 2459251.50420
            P (Orbital period in years)     : 556.57

            Epoch                           : 2025 Jun 30
            Reference                       : MPEC 2021-W31

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

The light curve chart below shows the estimated development of the comet's magnitude. Blue and black dots are visual and photometric CCD observations respectively from COBS or the MPC. 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. (15.00 + 5 log[∆] + 10.00 log[r]).

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.
A more printer-friendly version of the same chart can be found further down this page as well.

The following chart shows the current location of the comet in a smaller, upside-down telescopic field of view.

A printable version of the short-term path of the comet in a field of view that is optimized for (~10x50) binoculars and finderscopes.

Ephemerides:

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-07-02 00:00 UT   10 44 29.8   -23 13 23    13.056   12.823   74.6    4.4   124   31.7 
2025-07-02 01:52 UT   10 44 30.7   -23 13 20    13.057   12.824   74.5    4.4   124   31.7 
2025-07-03 00:00 UT   10 44 42.1   -23 12 38    13.075   12.829   73.8    4.4   125   31.7 
2025-07-04 00:00 UT   10 44 54.6   -23 11 56    13.095   12.835   73.0    4.3   125   31.7 
2025-07-05 00:00 UT   10 45 07.3   -23 11 17    13.115   12.841   72.2    4.3   125   31.7 
2025-07-06 00:00 UT   10 45 20.2   -23 10 40    13.134   12.847   71.4    4.3   126   31.7 
2025-07-07 00:00 UT   10 45 33.4   -23 10 05    13.153   12.853   70.6    4.3   126   31.7 
2025-07-08 00:00 UT   10 45 46.7   -23 09 33    13.173   12.858   69.8    4.3   127   31.7 
2025-07-09 00:00 UT   10 46 00.3   -23 09 04    13.192   12.864   69.1    4.2   127   31.7 
2025-07-10 00:00 UT   10 46 14.0   -23 08 37    13.211   12.870   68.3    4.2   128   31.7 
2025-07-11 00:00 UT   10 46 27.9   -23 08 12    13.230   12.876   67.5    4.2   128   31.7 
2025-07-12 00:00 UT   10 46 42.1   -23 07 51    13.249   12.881   66.7    4.2   129   31.7 

    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.