C/2021 K3 (Catalina)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	2 Feb 2022	21.1	5.219 AU	6.155 AU	19h54m	-22°02'	16.8°	3.1°	255°
Nearest approach	28 Jun 2022	20.5	5.334 AU	4.354 AU	19h00m	-39°01'	162.7°	3.3°	333°
Today	18 Sep 2026	26.6	12.478 AU	13.198 AU	11h07m	-39°56'	42.6°	3.1°	193°

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)                : 1.0026690
    q (Perihelion distance)         : 5.2192710
    i (Inclination)                 : 134.79470
    Ω (Longitude of ascending node) : 114.51700
    ω (Argument of perihelion)      : 181.94010
    L (Longitude of perihelion)     : 113.14980
    B (Latitude of perihelion)      : -1.37663
    T (Time of perihelion passage)  : 2459612.72410

    Epoch                           : 2026 Sep 17
    Reference                       : MPC194174

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-09-17 00:00 UT   11 07 26.4   -39 55 41    13.188   12.471   42.9    3.1   191   26.6 
2026-09-18 00:00 UT   11 07 43.1   -39 56 40    13.196   12.477   42.7    3.1   192   26.6 
2026-09-18 07:15 UT   11 07 48.1   -39 56 59    13.198   12.478   42.6    3.1   193   26.6 
2026-09-19 00:00 UT   11 07 59.6   -39 57 43    13.204   12.482   42.5    3.1   193   26.6 
2026-09-20 00:00 UT   11 08 16.2   -39 58 48    13.212   12.487   42.3    3.1   195   26.6 
2026-09-21 00:00 UT   11 08 32.6   -39 59 56    13.219   12.492   42.1    3.1   196   26.6 
2026-09-22 00:00 UT   11 08 48.9   -40 01 07    13.226   12.498   41.9    3.1   197   26.6 
2026-09-23 00:00 UT   11 09 05.2   -40 02 21    13.233   12.503   41.7    3.1   199   26.6 
2026-09-24 00:00 UT   11 09 21.3   -40 03 37    13.240   12.508   41.6    3.1   200   26.6 
2026-09-25 00:00 UT   11 09 37.4   -40 04 56    13.247   12.513   41.5    3.0   201   26.6 
2026-09-26 00:00 UT   11 09 53.4   -40 06 17    13.253   12.519   41.4    3.0   203   26.6 
2026-09-27 00:00 UT   11 10 09.2   -40 07 41    13.259   12.524   41.3    3.0   204   26.6 
2026-09-28 00:00 UT   11 10 25.0   -40 09 07    13.266   12.529   41.2    3.0   206   26.6 

    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.