C/2013 US10 (Catalina)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	12 Nov 2015	6.3	0.814 AU	1.752 AU	14h15m	-18°29'	12.5°	15.3°	268°
Nearest approach	15 Jan 2016	6.2	1.406 AU	0.747 AU	13h41m	+55°22'	107.9°	41.7°	282°
Today	23 Nov 2025	23.1	25.373 AU	24.497 AU	02h06m	+34°25'	151.9°	1.0°	113°

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. This lightcurve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 5.8 + 5 log[∆] + 7.4 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/2013 US10 (Catalina) are:

    e (Eccentricity)                : 1.0001430
    q (Perihelion distance)         : 0.8144010
    i (Inclination)                 : 148.90140
    Ω (Longitude of ascending node) : 186.21950
    ω (Argument of perihelion)      : 340.26040
    L (Longitude of perihelion)     : 203.29962
    B (Latitude of perihelion)      : -10.04665
    T (Time of perihelion passage)  : 2457338.81090

    Epoch                           : 2025 Nov 22
    Reference                       : MPC110080

    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   02 06 44.3   +34 27 47    24.479   25.365  153.1    1.0   116   23.1 
2025-11-23 00:00 UT   02 06 34.0   +34 26 36    24.489   25.369  152.4    1.0   114   23.1 
2025-11-23 18:01 UT   02 06 26.3   +34 25 42    24.497   25.373  151.9    1.0   113   23.1 
2025-11-24 00:00 UT   02 06 23.8   +34 25 24    24.500   25.374  151.7    1.1   112   23.1 
2025-11-25 00:00 UT   02 06 13.7   +34 24 12    24.510   25.379  151.0    1.1   111   23.1 
2025-11-26 00:00 UT   02 06 03.7   +34 22 59    24.521   25.384  150.3    1.1   109   23.1 
2025-11-27 00:00 UT   02 05 53.8   +34 21 46    24.532   25.389  149.5    1.1   108   23.1 
2025-11-28 00:00 UT   02 05 44.0   +34 20 33    24.544   25.393  148.7    1.2   106   23.1 
2025-11-29 00:00 UT   02 05 34.3   +34 19 19    24.556   25.398  148.0    1.2   105   23.1 
2025-11-30 00:00 UT   02 05 24.8   +34 18 05    24.568   25.403  147.2    1.2   104   23.1 
2025-12-01 00:00 UT   02 05 15.4   +34 16 51    24.580   25.408  146.3    1.2   102   23.1 
2025-12-02 00:00 UT   02 05 06.1   +34 15 37    24.593   25.412  145.5    1.3   101   23.1 
2025-12-03 00:00 UT   02 04 56.9   +34 14 22    24.606   25.417  144.7    1.3   100   23.1 

    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.