C/2013 US10 (Catalina)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	11 Nov 2015	6.3	0.816 AU	1.756 AU	14h13m	-18°22'	12.3°	15.0°	267°
Nearest approach	15 Jan 2016	6.3	1.412 AU	0.751 AU	13h38m	+55°24'	108.2°	41.5°	281°
Today	18 Sep 2026	23.4	26.779 AU	26.135 AU	02h15m	+34°39'	129.0°	1.7°	232°

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)                : 1.0001550
    q (Perihelion distance)         : 0.8161600
    i (Inclination)                 : 148.94850
    Ω (Longitude of ascending node) : 186.11830
    ω (Argument of perihelion)      : 340.18710
    L (Longitude of perihelion)     : 203.27116
    B (Latitude of perihelion)      : -10.06895
    T (Time of perihelion passage)  : 2457338.17090

    Epoch                           : 2026 Sep 18
    Reference                       : MPC194135

    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   02 15 51.2   +34 40 01    26.148   26.771  127.4    1.7   233   23.4 
2026-09-18 00:00 UT   02 15 42.9   +34 39 56    26.140   26.776  128.3    1.7   233   23.4 
2026-09-18 17:51 UT   02 15 36.7   +34 39 52    26.135   26.779  129.0    1.7   232   23.4 
2026-09-19 00:00 UT   02 15 34.6   +34 39 50    26.133   26.780  129.2    1.7   232   23.4 
2026-09-20 00:00 UT   02 15 26.1   +34 39 43    26.126   26.785  130.1    1.6   232   23.4 
2026-09-21 00:00 UT   02 15 17.5   +34 39 35    26.119   26.790  131.0    1.6   231   23.4 
2026-09-22 00:00 UT   02 15 08.8   +34 39 26    26.112   26.794  131.9    1.6   230   23.4 
2026-09-23 00:00 UT   02 14 60.0   +34 39 16    26.106   26.799  132.8    1.6   230   23.4 
2026-09-24 00:00 UT   02 14 51.1   +34 39 04    26.100   26.804  133.7    1.6   229   23.4 
2026-09-25 00:00 UT   02 14 42.1   +34 38 52    26.094   26.808  134.6    1.5   228   23.4 
2026-09-26 00:00 UT   02 14 32.9   +34 38 38    26.088   26.813  135.5    1.5   228   23.4 
2026-09-27 00:00 UT   02 14 23.7   +34 38 23    26.082   26.817  136.4    1.5   227   23.4 
2026-09-28 00:00 UT   02 14 14.4   +34 38 07    26.077   26.822  137.2    1.5   226   23.4 

    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.