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	18 Sep 2025	32.7	18.668 AU	19.592 AU	10h26m	-09°27'	22.5°	1.2°	241°

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.)

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)
        

The light curve chart below shows the estimated development of the comet's magnitude. Blue and black dots are visual and photometric CCD observations respectively from COBS or the MPC. 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. (13.50 + 5 log[∆] + 10.00 log[r]).

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.
A more printer-friendly version of the same chart can be found further down this page as well.

The following chart shows the current location of the comet in a smaller, upside-down telescopic field of view.

A printable version of the short-term path of the comet in a field of view that is optimized for (~10x50) binoculars and finderscopes.

Ephemerides:

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2025-09-18 00:00 UT   10 26 12.3   -09 26 16    19.594   18.667   22.0    1.2   240   32.7 
2025-09-18 21:41 UT   10 26 23.0   -09 27 31    19.592   18.668   22.5    1.2   241   32.7 
2025-09-19 00:00 UT   10 26 24.1   -09 27 39    19.592   18.668   22.5    1.2   242   32.7 
2025-09-20 00:00 UT   10 26 35.9   -09 29 02    19.590   18.670   23.1    1.2   243   32.7 
2025-09-21 00:00 UT   10 26 47.7   -09 30 25    19.587   18.672   23.7    1.2   245   32.7 
2025-09-22 00:00 UT   10 26 59.3   -09 31 49    19.584   18.674   24.3    1.3   247   32.7 
2025-09-23 00:00 UT   10 27 10.9   -09 33 14    19.581   18.675   24.9    1.3   249   32.7 
2025-09-24 00:00 UT   10 27 22.4   -09 34 38    19.577   18.677   25.6    1.3   250   32.7 
2025-09-25 00:00 UT   10 27 33.9   -09 36 04    19.573   18.679   26.2    1.4   252   32.7 
2025-09-26 00:00 UT   10 27 45.2   -09 37 30    19.569   18.681   26.9    1.4   253   32.7 
2025-09-27 00:00 UT   10 27 56.5   -09 38 56    19.565   18.682   27.6    1.4   254   32.7 
2025-09-28 00:00 UT   10 28 07.7   -09 40 23    19.560   18.684   28.3    1.5   256   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.