C/2020 R4 (ATLAS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	2 Mar 2021	10.7	1.020 AU	1.704 AU	20h40m	-11°24'	32.6°	31.6°	266°
Nearest approach	23 Apr 2021	9.2	1.336 AU	0.458 AU	16h15m	+29°01'	127.6°	36.6°	222°
Today	2 Oct 2025	29.2	14.316 AU	14.805 AU	08h47m	+13°27'	59.0°	3.4°	283°

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 R4 (ATLAS) are:

            e (Eccentricity)                : 0.9894620
            q (Perihelion distance)         : 1.0200660
            i (Inclination)                 : 164.39800
            Ω (Longitude of ascending node) : 323.22700
            ω (Argument of perihelion)      : 46.49280
            L (Longitude of perihelion)     : 277.80906
            B (Latitude of perihelion)      : 11.24873
            T (Time of perihelion passage)  : 2459275.61120
            P (Orbital period in years)     : 952.37

            Epoch                           : 2025 Oct 01
            Reference                       : MPEC 2022-K19

            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 gray curve is based on the absolute magnitude and slope parameter as calculated from the original MPEC, or the latest values provided by the MPC (13.50 + 5 log[∆] + 10.00 log[r]), whereas the red curve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 9.40 + 5 log[∆] + 12.06 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
2025-10-02 00:00 UT   08 47 22.0   +13 28 24    14.812   14.311   58.2    3.4   283   29.2 
2025-10-02 20:31 UT   08 47 26.9   +13 27 45    14.805   14.316   59.0    3.4   283   29.2 
2025-10-03 00:00 UT   08 47 27.8   +13 27 38    14.804   14.317   59.2    3.4   283   29.2 
2025-10-04 00:00 UT   08 47 33.3   +13 26 53    14.794   14.323   60.1    3.5   283   29.2 
2025-10-05 00:00 UT   08 47 38.6   +13 26 08    14.785   14.329   61.1    3.5   283   29.2 
2025-10-06 00:00 UT   08 47 43.7   +13 25 25    14.776   14.335   62.1    3.5   283   29.2 
2025-10-07 00:00 UT   08 47 48.5   +13 24 42    14.766   14.341   63.0    3.6   283   29.2 
2025-10-08 00:00 UT   08 47 53.1   +13 23 60    14.757   14.347   64.0    3.6   283   29.2 
2025-10-09 00:00 UT   08 47 57.5   +13 23 18    14.747   14.353   64.9    3.6   283   29.2 
2025-10-10 00:00 UT   08 48 01.6   +13 22 38    14.737   14.359   65.9    3.6   284   29.2 
2025-10-11 00:00 UT   08 48 05.4   +13 21 58    14.727   14.365   66.9    3.7   284   29.2 
2025-10-12 00:00 UT   08 48 09.1   +13 21 19    14.717   14.371   67.8    3.7   284   29.2 

    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.