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C/2021 K3 (Catalina)
ephemeris date magn radius delta ra dec elong phase PA
Perihelion3 Feb 202221.15.226 AU6.155 AU 19h55m-22°01'17.8°3.3°255°
Nearest approach28 Jun 202220.55.338 AU4.359 AU 19h01m-38°56'162.8°3.2°333°
Today23 Nov 202525.710.893 AU11.438 AU 11h59m-47°14'54.4°4.2°262°
C/2021 K3 (Catalina)- 2025-11-23
astro.vanbuitenen.nl


 
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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.)


Light curve

The light curve chart below shows the estimated development of the comet's magnitude. Blue and black dots are visual and photometric CCD observations from COBS. 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. (10.0 + 5 log[∆] + 10.0 log[r]). An additional green curve is displayed when an increase in apparent brightness is expected due to forward scattering of sunlight, which occurs when a dust-rich comet is located between the Earth and the Sun. (See Marcus 2007)



Charts

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.




Orbital elements

The orbital elements of C/2021 K3 (Catalina) are: 

    e (Eccentricity)                : 1.0039540
    q (Perihelion distance)         : 5.2255460
    i (Inclination)                 : 134.78040
    Ω (Longitude of ascending node) : 114.61460
    ω (Argument of perihelion)      : 181.98830
    L (Longitude of perihelion)     : 113.21378
    B (Latitude of perihelion)      : -1.41118
    T (Time of perihelion passage)  : 2459613.95840

    Epoch                           : 2025 Nov 22
    Reference                       : MPEC 2022-L66

    Classification(s):              : Nearly isotropic; New (a > 10000 AU)

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-11-22 00:00 UT   11 59 27.0   -47 09 39    11.442   10.885   53.5    4.2   260   25.7 
2025-11-23 00:00 UT   11 59 32.5   -47 12 51    11.440   10.890   54.1    4.2   261   25.7 
2025-11-23 15:04 UT   11 59 35.8   -47 14 53    11.438   10.893   54.4    4.2   262   25.7 
2025-11-24 00:00 UT   11 59 37.7   -47 16 05    11.437   10.895   54.6    4.2   262   25.7 
2025-11-25 00:00 UT   11 59 42.4   -47 19 19    11.434   10.901   55.2    4.3   263   25.7 
2025-11-26 00:00 UT   11 59 46.7   -47 22 34    11.430   10.906   55.8    4.3   264   25.7 
2025-11-27 00:00 UT   11 59 50.6   -47 25 49    11.427   10.911   56.4    4.3   265   25.7 
2025-11-28 00:00 UT   11 59 54.0   -47 29 05    11.423   10.917   56.9    4.3   266   25.7 
2025-11-29 00:00 UT   11 59 57.0   -47 32 21    11.419   10.922   57.5    4.4   267   25.7 
2025-11-30 00:00 UT   11 59 59.5   -47 35 38    11.415   10.927   58.1    4.4   268   25.7 
2025-12-01 00:00 UT   12 00 01.6   -47 38 54    11.411   10.933   58.7    4.4   269   25.7 
2025-12-02 00:00 UT   12 00 03.2   -47 42 11    11.407   10.938   59.4    4.4   270   25.7 
2025-12-03 00:00 UT   12 00 04.4   -47 45 29    11.403   10.943   60.0    4.5   270   25.7 




    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.

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