C/2013 US10 (Catalina)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	11 Nov 2015	6.3	0.815 AU	1.754 AU	14h14m	-18°24'	12.4°	15.1°	268°
Nearest approach	15 Jan 2016	6.2	1.410 AU	0.750 AU	13h39m	+55°23'	108.1°	41.6°	282°
Today	16 Jul 2026	23.4	26.480 AU	26.799 AU	02h19m	+34°12'	70.6°	2.1°	257°

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)                : 1.0001560
    q (Perihelion distance)         : 0.8152740
    i (Inclination)                 : 148.93640
    Ω (Longitude of ascending node) : 186.13800
    ω (Argument of perihelion)      : 340.19320
    L (Longitude of perihelion)     : 203.28342
    B (Latitude of perihelion)      : -10.06951
    T (Time of perihelion passage)  : 2457338.37100

    Epoch                           : 2026 Jul 15
    Reference                       : MPC194135

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-07-15 00:00 UT   02 19 18.1   +34 11 48    26.813   26.474   69.4    2.1   257   23.4 
2026-07-16 00:00 UT   02 19 20.1   +34 12 37    26.803   26.478   70.3    2.1   257   23.4 
2026-07-16 08:55 UT   02 19 20.8   +34 12 55    26.799   26.480   70.6    2.1   257   23.4 
2026-07-17 00:00 UT   02 19 21.9   +34 13 26    26.793   26.483   71.2    2.1   257   23.4 
2026-07-18 00:00 UT   02 19 23.6   +34 14 14    26.782   26.488   72.1    2.1   256   23.4 
2026-07-19 00:00 UT   02 19 25.1   +34 15 01    26.772   26.492   72.9    2.1   256   23.4 
2026-07-20 00:00 UT   02 19 26.4   +34 15 48    26.761   26.497   73.8    2.1   256   23.4 
2026-07-21 00:00 UT   02 19 27.6   +34 16 35    26.750   26.502   74.7    2.1   255   23.4 
2026-07-22 00:00 UT   02 19 28.6   +34 17 21    26.740   26.506   75.6    2.1   255   23.4 
2026-07-23 00:00 UT   02 19 29.4   +34 18 07    26.729   26.511   76.5    2.1   255   23.4 
2026-07-24 00:00 UT   02 19 30.1   +34 18 51    26.718   26.516   77.4    2.1   254   23.4 
2026-07-25 00:00 UT   02 19 30.6   +34 19 36    26.707   26.520   78.3    2.1   254   23.4 
2026-07-26 00:00 UT   02 19 30.9   +34 20 20    26.696   26.525   79.2    2.2   254   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.