C/2013 US10 (Catalina)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	16 Nov 2015	6.3	0.820 AU	1.739 AU	14h24m	-19°17'	14.6°	17.6°	270°
Nearest approach	17 Jan 2016	6.1	1.378 AU	0.718 AU	13h53m	+54°52'	107.2°	43.0°	282°
Today	24 Oct 2025	23.0	25.242 AU	24.325 AU	02h11m	+34°56'	156.7°	0.9°	190°

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)                : 1.0006210
    q (Perihelion distance)         : 0.8202940
    i (Inclination)                 : 148.75930
    Ω (Longitude of ascending node) : 186.41870
    ω (Argument of perihelion)      : 340.59350
    L (Longitude of perihelion)     : 203.18104
    B (Latitude of perihelion)      : -9.92307
    T (Time of perihelion passage)  : 2457343.40160

    Epoch                           : 2020 Dec 03
    Reference                       : MPC110080

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-10-23 00:00 UT   02 12 16.3   +34 57 37    24.322   25.234  155.8    0.9   194   23.0 
2025-10-24 00:00 UT   02 12 04.6   +34 56 50    24.324   25.239  156.3    0.9   191   23.0 
2025-10-24 18:40 UT   02 11 55.6   +34 56 13    24.325   25.242  156.7    0.9   190   23.0 
2025-10-25 00:00 UT   02 11 53.0   +34 56 02    24.325   25.243  156.8    0.9   189   23.0 
2025-10-26 00:00 UT   02 11 41.3   +34 55 13    24.327   25.248  157.3    0.9   187   23.0 
2025-10-27 00:00 UT   02 11 29.6   +34 54 23    24.330   25.253  157.7    0.9   184   23.0 
2025-10-28 00:00 UT   02 11 18.0   +34 53 32    24.332   25.258  158.1    0.8   182   23.0 
2025-10-29 00:00 UT   02 11 06.3   +34 52 39    24.335   25.262  158.5    0.8   179   23.0 
2025-10-30 00:00 UT   02 10 54.7   +34 51 46    24.338   25.267  158.8    0.8   176   23.0 
2025-10-31 00:00 UT   02 10 43.0   +34 50 52    24.342   25.272  159.0    0.8   173   23.0 
2025-11-01 00:00 UT   02 10 31.4   +34 49 57    24.345   25.277  159.3    0.8   171   23.0 
2025-11-02 00:00 UT   02 10 19.8   +34 49 01    24.349   25.282  159.4    0.8   168   23.0 
2025-11-03 00:00 UT   02 10 08.2   +34 48 04    24.354   25.286  159.5    0.8   165   23.0 

    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.