C/2013 U1 (Catalina)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	6 Sep 2013	18.6	2.532 AU	1.656 AU	21h03m	+17°40'	142.6°	14.0°	128°
Perihelion	16 Nov 2013	19.0	2.434 AU	2.092 AU	21h53m	+04°41'	97.9°	23.7°	72°
Today	4 Oct 2026	32.9	19.286 AU	20.140 AU	10h37m	-10°03'	30.6°	1.5°	261°

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. The light curve is based on the absolute magnitude and slope parameter as calculated from an MPEC, or the latest values provided by the minor planet center. (13.5 + 5 log[∆] + 10.0 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 U1 (Catalina) are:

    e (Eccentricity)                : 0.7952620
    q (Perihelion distance)         : 2.4337520
    i (Inclination)                 : 23.95480
    Ω (Longitude of ascending node) : 211.07300
    ω (Argument of perihelion)      : 143.31820
    L (Longitude of perihelion)     : 176.82897
    B (Latitude of perihelion)      : 14.03661
    T (Time of perihelion passage)  : 2456612.97580
    P (Orbital period in years)     : 40.98

    Epoch                           : 2026 May 29
    Reference                       : MPC194134

    Classification(s):              : Nearly isotropic; Returning (a < 10000 AU); Halley type (P < 200 years)

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-10-03 00:00 UT   10 37 07.9   -10 01 41    20.146   19.284   29.8    1.5   260   32.9 
2026-10-04 00:00 UT   10 37 18.4   -10 03 06    20.140   19.286   30.6    1.5   261   32.9 
2026-10-04 01:12 UT   10 37 18.9   -10 03 10    20.140   19.286   30.6    1.5   261   32.9 
2026-10-05 00:00 UT   10 37 28.8   -10 04 32    20.134   19.287   31.3    1.5   262   32.9 
2026-10-06 00:00 UT   10 37 39.1   -10 05 57    20.128   19.289   32.1    1.6   263   32.9 
2026-10-07 00:00 UT   10 37 49.4   -10 07 23    20.122   19.290   32.9    1.6   264   32.9 
2026-10-08 00:00 UT   10 37 59.5   -10 08 49    20.115   19.292   33.7    1.6   265   32.9 
2026-10-09 00:00 UT   10 38 09.5   -10 10 16    20.108   19.293   34.5    1.7   266   32.9 
2026-10-10 00:00 UT   10 38 19.4   -10 11 42    20.101   19.295   35.3    1.7   267   32.9 
2026-10-11 00:00 UT   10 38 29.2   -10 13 09    20.094   19.296   36.1    1.7   268   32.9 
2026-10-12 00:00 UT   10 38 38.8   -10 14 36    20.086   19.298   36.9    1.8   268   32.9 
2026-10-13 00:00 UT   10 38 48.4   -10 16 03    20.079   19.299   37.7    1.8   269   32.9 
2026-10-14 00:00 UT   10 38 57.8   -10 17 30    20.071   19.301   38.6    1.8   270   32.9 

    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.