C/2021 C3 (Catalina)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	10 Feb 2021	18.7	2.275 AU	1.669 AU	13h33m	-13°29'	115.5°	23.1°	293°
Nearest approach	13 Mar 2021	18.2	2.300 AU	1.327 AU	12h22m	+12°12'	164.6°	6.6°	234°
Today	24 Feb 2026	31.3	14.098 AU	14.547 AU	00h33m	+44°56'	61.2°	3.5°	35°

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. (14.0 + 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 C3 (Catalina) are:

    e (Eccentricity)                : 0.9622900
    q (Perihelion distance)         : 2.2750460
    i (Inclination)                 : 122.22350
    Ω (Longitude of ascending node) : 181.83080
    ω (Argument of perihelion)      : 356.96990
    L (Longitude of perihelion)     : 183.44760
    B (Latitude of perihelion)      : -2.56305
    T (Time of perihelion passage)  : 2459256.37010
    P (Orbital period in years)     : 468.60

    Epoch                           : 2025 Nov 12
    Reference                       : MPEC 2024-M41

    Classification(s):              : Nearly isotropic; Returning (a < 10000 AU); External (P > 200 years)

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-02-23 00:00 UT   00 32 55.2   +44 57 39    14.523   14.090   62.2    3.6    37   31.3 
2026-02-24 00:00 UT   00 33 12.3   +44 56 32    14.540   14.095   61.5    3.5    36   31.3 
2026-02-24 10:34 UT   00 33 19.9   +44 56 04    14.547   14.098   61.2    3.5    35   31.3 
2026-02-25 00:00 UT   00 33 29.6   +44 55 29    14.556   14.101   60.8    3.5    35   31.3 
2026-02-26 00:00 UT   00 33 46.9   +44 54 29    14.573   14.106   60.1    3.5    34   31.3 
2026-02-27 00:00 UT   00 34 04.5   +44 53 31    14.589   14.112   59.4    3.5    34   31.3 
2026-02-28 00:00 UT   00 34 22.2   +44 52 37    14.606   14.117   58.7    3.4    33   31.3 
2026-03-01 00:00 UT   00 34 40.0   +44 51 45    14.622   14.123   58.0    3.4    32   31.3 
2026-03-02 00:00 UT   00 34 57.9   +44 50 57    14.638   14.128   57.3    3.4    31   31.3 
2026-03-03 00:00 UT   00 35 16.0   +44 50 12    14.654   14.134   56.7    3.4    31   31.3 
2026-03-04 00:00 UT   00 35 34.2   +44 49 29    14.669   14.139   56.0    3.3    30   31.3 
2026-03-05 00:00 UT   00 35 52.5   +44 48 50    14.685   14.145   55.3    3.3    29   31.3 
2026-03-06 00:00 UT   00 36 10.9   +44 48 13    14.700   14.150   54.7    3.3    28   31.3 

    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.