C/2021 P4 (ATLAS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	13 Jul 2022	10.2	1.114 AU	1.957 AU	09h14m	+27°59'	24.4°	22.2°	81°
Perihelion	30 Jul 2022	10.0	1.078 AU	1.975 AU	09h59m	+14°20'	20.0°	18.8°	105°
Today	18 Aug 2025	27.5	10.810 AU	9.976 AU	22h43m	-47°30'	143.8°	3.2°	338°

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/2021 P4 (ATLAS) are:

            e (Eccentricity)                : 0.9963610
            q (Perihelion distance)         : 1.0784950
            i (Inclination)                 : 56.38250
            Ω (Longitude of ascending node) : 347.99960
            ω (Argument of perihelion)      : 175.81060
            L (Longitude of perihelion)     : 345.67729
            B (Latitude of perihelion)      : 3.48778
            T (Time of perihelion passage)  : 2459790.94560
            P (Orbital period in years)     : 5102.16

            Epoch                           : 2025 Aug 18
            Reference                       : MPEC 2023-A50

            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 (9.50 + 5 log[∆] + 10.00 log[r]), whereas the red curve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 8.04 + 5 log[∆] + 14.01 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
2025-08-18 00:00 UT   22 43 55.0   -47 28 47     9.969   10.804  143.9    3.2   337   27.5 
2025-08-18 20:08 UT   22 43 29.4   -47 30 08     9.976   10.810  143.8    3.2   338   27.5 
2025-08-19 00:00 UT   22 43 24.5   -47 30 23     9.977   10.811  143.8    3.2   339   27.5 
2025-08-20 00:00 UT   22 42 54.0   -47 31 55     9.985   10.818  143.7    3.2   341   27.5 
2025-08-21 00:00 UT   22 42 23.3   -47 33 24     9.993   10.825  143.6    3.2   342   27.5 
2025-08-22 00:00 UT   22 41 52.6   -47 34 48    10.002   10.831  143.4    3.2   344   27.5 
2025-08-23 00:00 UT   22 41 21.8   -47 36 08    10.011   10.838  143.3    3.2   346   27.5 
2025-08-24 00:00 UT   22 40 50.9   -47 37 24    10.020   10.845  143.1    3.2   348   27.5 
2025-08-25 00:00 UT   22 40 20.0   -47 38 36    10.029   10.852  142.8    3.2   350   27.6 
2025-08-26 00:00 UT   22 39 49.1   -47 39 44    10.039   10.859  142.6    3.2   351   27.6 
2025-08-27 00:00 UT   22 39 18.1   -47 40 48    10.049   10.866  142.3    3.3   353   27.6 
2025-08-28 00:00 UT   22 38 47.2   -47 41 47    10.059   10.873  142.0    3.3   355   27.6 

    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.