C/2021 K1 (ATLAS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	2 May 2021	16.1	2.502 AU	2.899 AU	23h05m	-06°56'	57.2°	19.8°	247°
Nearest approach	12 Sep 2021	15.6	2.812 AU	1.888 AU	01h16m	-10°36'	151.2°	9.9°	281°
Today	20 May 2025	25.2	10.401 AU	11.166 AU	06h31m	+13°24'	39.1°	3.5°	105°

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 K1 (ATLAS) are:

            e (Eccentricity)                : 0.8015530
            q (Perihelion distance)         : 2.5020010
            i (Inclination)                 : 16.27130
            Ω (Longitude of ascending node) : 140.92340
            ω (Argument of perihelion)      : 184.22730
            L (Longitude of perihelion)     : 144.98196
            B (Latitude of perihelion)      : -1.18344
            T (Time of perihelion passage)  : 2459336.99870
            P (Orbital period in years)     : 44.77

            Epoch                           : 2025 May 19
            Reference                       : MPEC 2022-O08

            Classification(s):              : Nearly isotropic; Returning (a < 10000 AU); Halley type (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 (11.00 + 5 log[∆] + 10.00 log[r]), whereas the red curve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 9.78 + 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
2025-05-20 00:00 UT   06 31 15.5   +13 24 09    11.153   10.397   39.9    3.6   105   25.2 
2025-05-20 20:15 UT   06 31 33.7   +13 24 34    11.166   10.401   39.1    3.5   105   25.2 
2025-05-21 00:00 UT   06 31 37.1   +13 24 38    11.168   10.402   39.0    3.5   106   25.2 
2025-05-22 00:00 UT   06 31 58.8   +13 25 06    11.183   10.406   38.2    3.4   106   25.2 
2025-05-23 00:00 UT   06 32 20.7   +13 25 32    11.198   10.411   37.3    3.4   106   25.2 
2025-05-24 00:00 UT   06 32 42.7   +13 25 57    11.212   10.416   36.5    3.3   107   25.2 
2025-05-25 00:00 UT   06 33 04.9   +13 26 22    11.226   10.420   35.7    3.2   107   25.2 
2025-05-26 00:00 UT   06 33 27.3   +13 26 45    11.240   10.425   34.8    3.2   108   25.2 
2025-05-27 00:00 UT   06 33 49.8   +13 27 07    11.254   10.429   34.0    3.1   108   25.2 
2025-05-28 00:00 UT   06 34 12.4   +13 27 28    11.267   10.434   33.2    3.0   109   25.2 
2025-05-29 00:00 UT   06 34 35.2   +13 27 48    11.280   10.438   32.3    3.0   109   25.2 
2025-05-30 00:00 UT   06 34 58.1   +13 28 07    11.294   10.443   31.5    2.9   110   25.2 

    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.