C/2013 U1 (Catalina)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	5 Sep 2013	18.6	2.533 AU	1.657 AU	21h03m	+17°39'	142.6°	14.0°	128°
Perihelion	16 Nov 2013	19.0	2.434 AU	2.094 AU	21h53m	+04°40'	97.8°	23.7°	72°
Today	18 May 2026	32.7	19.068 AU	18.834 AU	10h16m	-09°16'	101.9°	3.0°	108°

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)                : 0.7952800
    q (Perihelion distance)         : 2.4335420
    i (Inclination)                 : 23.95590
    Ω (Longitude of ascending node) : 211.06990
    ω (Argument of perihelion)      : 143.32120
    L (Longitude of perihelion)     : 176.82901
    B (Latitude of perihelion)      : 14.03622
    T (Time of perihelion passage)  : 2456613.12380
    P (Orbital period in years)     : 40.98

    Epoch                           : 2026 May 17
    Reference                       : MPEC 2026-E44

    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
2026-05-17 00:00 UT   10 16 36.4   -09 18 05    18.812   19.066  103.1    3.0   108   32.7 
2026-05-18 00:00 UT   10 16 36.5   -09 16 57    18.829   19.068  102.2    3.0   108   32.7 
2026-05-18 07:47 UT   10 16 36.5   -09 16 35    18.834   19.068  101.9    3.0   108   32.7 
2026-05-19 00:00 UT   10 16 36.7   -09 15 50    18.846   19.070  101.3    3.0   108   32.7 
2026-05-20 00:00 UT   10 16 37.2   -09 14 45    18.863   19.071  100.3    3.0   109   32.7 
2026-05-21 00:00 UT   10 16 37.9   -09 13 41    18.881   19.073   99.4    3.0   109   32.7 
2026-05-22 00:00 UT   10 16 38.8   -09 12 38    18.898   19.074   98.5    3.0   109   32.7 
2026-05-23 00:00 UT   10 16 39.9   -09 11 36    18.915   19.076   97.6    3.0   110   32.7 
2026-05-24 00:00 UT   10 16 41.1   -09 10 35    18.933   19.078   96.7    3.0   110   32.7 
2026-05-25 00:00 UT   10 16 42.6   -09 09 35    18.950   19.079   95.8    3.0   110   32.7 
2026-05-26 00:00 UT   10 16 44.3   -09 08 37    18.968   19.081   94.9    3.0   111   32.7 
2026-05-27 00:00 UT   10 16 46.1   -09 07 40    18.985   19.082   94.0    3.0   111   32.7 
2026-05-28 00:00 UT   10 16 48.2   -09 06 44    19.003   19.084   93.1    3.0   111   32.7 

    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.