C/2013 US10 (Catalina)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	12 Nov 2015	6.3	0.814 AU	1.753 AU	14h14m	-18°27'	12.4°	15.2°	268°
Nearest approach	15 Jan 2016	6.2	1.408 AU	0.748 AU	13h40m	+55°23'	108.0°	41.7°	282°
Today	14 May 2026	23.4	26.186 AU	27.123 AU	02h13m	+33°17'	21.6°	0.8°	308°

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)         : 0.8141820
    i (Inclination)                 : 148.92250
    Ω (Longitude of ascending node) : 186.16080
    ω (Argument of perihelion)      : 340.19890
    L (Longitude of perihelion)     : 203.29882
    B (Latitude of perihelion)      : -10.07079
    T (Time of perihelion passage)  : 2457338.59120

    Epoch                           : 2026 May 13
    Reference                       : MPEC 2026-E44

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-05-13 00:00 UT   02 12 51.3   +33 16 32    27.120   26.179   20.9    0.8   312   23.4 
2026-05-14 00:00 UT   02 13 00.3   +33 17 19    27.122   26.184   21.4    0.8   310   23.4 
2026-05-14 13:18 UT   02 13 05.3   +33 17 45    27.123   26.186   21.6    0.8   308   23.4 
2026-05-15 00:00 UT   02 13 09.2   +33 18 07    27.124   26.189   21.8    0.8   307   23.4 
2026-05-16 00:00 UT   02 13 18.1   +33 18 54    27.125   26.193   22.3    0.8   305   23.4 
2026-05-17 00:00 UT   02 13 26.9   +33 19 43    27.126   26.198   22.8    0.9   303   23.4 
2026-05-18 00:00 UT   02 13 35.7   +33 20 31    27.127   26.203   23.3    0.9   301   23.4 
2026-05-19 00:00 UT   02 13 44.4   +33 21 21    27.128   26.207   23.9    0.9   300   23.4 
2026-05-20 00:00 UT   02 13 53.0   +33 22 10    27.129   26.212   24.5    0.9   298   23.4 
2026-05-21 00:00 UT   02 14 01.6   +33 23 00    27.129   26.217   25.1    0.9   296   23.4 
2026-05-22 00:00 UT   02 14 10.1   +33 23 50    27.129   26.221   25.7    1.0   294   23.4 
2026-05-23 00:00 UT   02 14 18.6   +33 24 41    27.129   26.226   26.3    1.0   293   23.4 
2026-05-24 00:00 UT   02 14 27.0   +33 25 32    27.128   26.231   27.0    1.0   291   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.