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C/2021 K3 (Catalina)
ephemeris date magn radius delta ra dec elong phase PA
Perihelion3 Feb 202221.15.225 AU6.155 AU 19h55m-22°01'17.8°3.3°255°
Nearest approach28 Jun 202220.55.338 AU4.358 AU 19h01m-38°56'162.8°3.2°333°
Today7 Dec 202525.710.968 AU11.381 AU 12h00m-48°00'62.9°4.6°274°
C/2021 K3 (Catalina)- 2025-12-07
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)                : 1.0039250
    q (Perihelion distance)         : 5.2253390
    i (Inclination)                 : 134.78040
    Ω (Longitude of ascending node) : 114.61480
    ω (Argument of perihelion)      : 181.98540
    L (Longitude of perihelion)     : 113.21602
    B (Latitude of perihelion)      : -1.40912
    T (Time of perihelion passage)  : 2459613.93590

    Epoch                           : 2025 Dec 06
    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
2025-12-06 00:00 UT   12 00 05.0   -47 55 21    11.389   10.959   61.9    4.5   273   25.7 
2025-12-07 00:00 UT   12 00 04.3   -47 58 38    11.384   10.965   62.5    4.6   274   25.7 
2025-12-07 14:44 UT   12 00 03.6   -48 00 39    11.381   10.968   62.9    4.6   274   25.7 
2025-12-08 00:00 UT   12 00 03.1   -48 01 55    11.379   10.970   63.2    4.6   275   25.7 
2025-12-09 00:00 UT   12 00 01.4   -48 05 12    11.373   10.975   63.8    4.6   276   25.7 
2025-12-10 00:00 UT   11 59 59.1   -48 08 29    11.368   10.981   64.5    4.6   276   25.7 
2025-12-11 00:00 UT   11 59 56.4   -48 11 45    11.363   10.986   65.2    4.7   277   25.7 
2025-12-12 00:00 UT   11 59 53.2   -48 15 01    11.357   10.991   65.8    4.7   278   25.7 
2025-12-13 00:00 UT   11 59 49.4   -48 18 16    11.351   10.997   66.5    4.7   279   25.7 
2025-12-14 00:00 UT   11 59 45.2   -48 21 31    11.345   11.002   67.2    4.7   280   25.7 
2025-12-15 00:00 UT   11 59 40.4   -48 24 45    11.340   11.007   67.9    4.8   281   25.7 
2025-12-16 00:00 UT   11 59 35.1   -48 27 58    11.334   11.013   68.6    4.8   281   25.7 
2025-12-17 00:00 UT   11 59 29.3   -48 31 11    11.327   11.018   69.3    4.8   282   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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