C/2013 U1 (Catalina)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	4 Sep 2013	18.6	2.520 AU	1.655 AU	20h49m	+17°24'	141.0°	14.6°	127°
Perihelion	20 Nov 2013	19.0	2.400 AU	2.140 AU	21h51m	+03°56'	92.8°	24.3°	70°
Today	1 Nov 2025	32.7	18.744 AU	19.267 AU	10h33m	-10°31'	57.0°	2.5°	281°

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)                : 0.7977070
    q (Perihelion distance)         : 2.4001990
    i (Inclination)                 : 23.96080
    Ω (Longitude of ascending node) : 211.11160
    ω (Argument of perihelion)      : 143.04200
    L (Longitude of perihelion)     : 176.60052
    B (Latitude of perihelion)      : 14.13256
    T (Time of perihelion passage)  : 2456617.49060
    P (Orbital period in years)     : 40.87

    Epoch                           : 2020 Sep 26
    Reference                       : MPC 86643

    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
2025-10-31 00:00 UT   10 33 11.3   -10 29 27    19.286   18.742   55.5    2.5   280   32.7 
2025-11-01 00:00 UT   10 33 18.1   -10 30 55    19.274   18.743   56.4    2.5   280   32.7 
2025-11-01 15:10 UT   10 33 22.3   -10 31 50    19.267   18.744   57.0    2.5   281   32.7 
2025-11-02 00:00 UT   10 33 24.7   -10 32 22    19.262   18.745   57.3    2.6   281   32.7 
2025-11-03 00:00 UT   10 33 31.1   -10 33 48    19.250   18.747   58.2    2.6   281   32.7 
2025-11-04 00:00 UT   10 33 37.3   -10 35 14    19.238   18.749   59.1    2.6   282   32.7 
2025-11-05 00:00 UT   10 33 43.4   -10 36 40    19.226   18.750   60.0    2.6   282   32.6 
2025-11-06 00:00 UT   10 33 49.3   -10 38 05    19.214   18.752   60.9    2.6   282   32.6 
2025-11-07 00:00 UT   10 33 55.0   -10 39 30    19.201   18.754   61.8    2.7   283   32.6 
2025-11-08 00:00 UT   10 34 00.5   -10 40 54    19.189   18.755   62.7    2.7   283   32.6 
2025-11-09 00:00 UT   10 34 05.8   -10 42 17    19.176   18.757   63.6    2.7   284   32.6 
2025-11-10 00:00 UT   10 34 11.0   -10 43 41    19.163   18.759   64.6    2.7   284   32.6 
2025-11-11 00:00 UT   10 34 16.0   -10 45 03    19.150   18.761   65.5    2.8   284   32.6 

    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.