C/2020 R4 (ATLAS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	2 Mar 2021	10.7	1.024 AU	1.704 AU	20h40m	-11°23'	32.8°	31.7°	266°
Nearest approach	23 Apr 2021	9.2	1.337 AU	0.459 AU	16h15m	+28°51'	127.8°	36.5°	222°
Today	19 Apr 2024	27.3	10.955 AU	10.794 AU	08h32m	+15°30'	96.6°	5.2°	104°

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)                : 0.9896720
            q (Perihelion distance)         : 1.0241010
            i (Inclination)                 : 164.43230
            Ω (Longitude of ascending node) : 323.26000
            ω (Argument of perihelion)      : 46.61590
            L (Longitude of perihelion)     : 277.71401
            B (Latitude of perihelion)      : 11.24747
            T (Time of perihelion passage)  : 2459275.86240
            P (Orbital period in years)     : 987.39

            Epoch                           : 2024 Apr 19
            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 9.37 + 5 log[∆] + 12.33 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
2024-04-19 00:00 UT   08 32 16.3   +15 30 34    10.773   10.949   97.4    5.2   104   27.3 
2024-04-19 20:38 UT   08 32 12.1   +15 30 56    10.794   10.955   96.6    5.2   104   27.3 
2024-04-20 00:00 UT   08 32 11.5   +15 30 59    10.797   10.956   96.4    5.2   104   27.3 
2024-04-21 00:00 UT   08 32 07.0   +15 31 23    10.821   10.962   95.4    5.2   104   27.4 
2024-04-22 00:00 UT   08 32 03.0   +15 31 45    10.845   10.969   94.4    5.2   104   27.4 
2024-04-23 00:00 UT   08 31 59.3   +15 32 06    10.869   10.976   93.4    5.2   104   27.4 
2024-04-24 00:00 UT   08 31 56.0   +15 32 26    10.893   10.983   92.5    5.2   104   27.4 
2024-04-25 00:00 UT   08 31 53.1   +15 32 44    10.917   10.989   91.5    5.3   104   27.4 
2024-04-26 00:00 UT   08 31 50.6   +15 33 01    10.941   10.996   90.5    5.3   104   27.4 
2024-04-27 00:00 UT   08 31 48.4   +15 33 16    10.965   11.003   89.5    5.2   104   27.4 
2024-04-28 00:00 UT   08 31 46.7   +15 33 30    10.989   11.010   88.5    5.2   104   27.4 
2024-04-29 00:00 UT   08 31 45.3   +15 33 42    11.013   11.016   87.6    5.2   104   27.4 

    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.