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°	41.8°	282°
Today	16 Nov 2025	23.1	25.338 AU	24.428 AU	02h07m	+34°34'	156.5°	0.9°	127°

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)                : 1.0001440
    q (Perihelion distance)         : 0.8142990
    i (Inclination)                 : 148.89950
    Ω (Longitude of ascending node) : 186.22260
    ω (Argument of perihelion)      : 340.26190
    L (Longitude of perihelion)     : 203.30107
    B (Latitude of perihelion)      : -10.04647
    T (Time of perihelion passage)  : 2457338.84550

    Epoch                           : 2025 Nov 15
    Reference                       : MPC110080

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-11-15 00:00 UT   02 07 59.1   +34 35 50    24.416   25.331  157.2    0.9   131   23.1 
2025-11-16 00:00 UT   02 07 48.2   +34 34 42    24.424   25.336  156.7    0.9   128   23.1 
2025-11-16 09:41 UT   02 07 43.8   +34 34 15    24.428   25.338  156.5    0.9   127   23.1 
2025-11-17 00:00 UT   02 07 37.3   +34 33 35    24.433   25.341  156.2    0.9   126   23.1 
2025-11-18 00:00 UT   02 07 26.6   +34 32 26    24.441   25.346  155.6    0.9   124   23.1 
2025-11-19 00:00 UT   02 07 15.9   +34 31 17    24.450   25.350  155.0    0.9   122   23.1 
2025-11-20 00:00 UT   02 07 05.3   +34 30 08    24.460   25.355  154.4    1.0   120   23.1 
2025-11-21 00:00 UT   02 06 54.7   +34 28 57    24.469   25.360  153.8    1.0   118   23.1 
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 
2025-11-24 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 

    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.