C/2018 W1 (Catalina)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	14 May 2019	11.2	1.351 AU	1.930 AU	04h22m	-20°19'	41.5°	29.7°	158°
Nearest approach	26 Jun 2019	12.3	1.481 AU	1.673 AU	07h17m	-36°09'	61.2°	37.0°	164°
Today	15 Sep 2025	52.1	16.203 AU	16.510 AU	16h13m	+22°48'	70.5°	3.4°	85°

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/2018 W1 (Catalina) are:

            e (Eccentricity)                : 0.9378970
            q (Perihelion distance)         : 1.3505600
            i (Inclination)                 : 83.38400
            Ω (Longitude of ascending node) : 233.62030
            ω (Argument of perihelion)      : 251.16040
            L (Longitude of perihelion)     : 252.27886
            B (Latitude of perihelion)      : -70.07234
            T (Time of perihelion passage)  : 2458617.69220
            P (Orbital period in years)     : 101.41

            Epoch                           : 2025 Sep 15
            Reference                       : MPEC 2021-P47

            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 gray curve is based on the absolute magnitude and slope parameter as calculated from the original MPEC, or the latest values provided by the MPC (15.50 + 5 log[∆] + 5.00 log[r]), whereas the red curve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 5.42 + 5 log[∆] + 33.55 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
2025-09-15 00:00 UT   16 13 52.9   +22 50 09    16.498   16.200   71.1    3.4    85   52.1 
2025-09-15 19:28 UT   16 13 57.3   +22 48 24    16.510   16.203   70.5    3.4    85   52.1 
2025-09-16 00:00 UT   16 13 58.4   +22 47 60    16.513   16.204   70.4    3.4    85   52.1 
2025-09-17 00:00 UT   16 14 04.1   +22 45 51    16.529   16.209   69.8    3.3    84   52.1 
2025-09-18 00:00 UT   16 14 10.0   +22 43 43    16.544   16.213   69.1    3.3    83   52.1 
2025-09-19 00:00 UT   16 14 16.2   +22 41 35    16.559   16.218   68.5    3.3    82   52.1 
2025-09-20 00:00 UT   16 14 22.6   +22 39 28    16.574   16.222   67.8    3.3    82   52.1 
2025-09-21 00:00 UT   16 14 29.3   +22 37 22    16.589   16.227   67.2    3.3    81   52.1 
2025-09-22 00:00 UT   16 14 36.1   +22 35 17    16.604   16.231   66.5    3.3    80   52.1 
2025-09-23 00:00 UT   16 14 43.2   +22 33 12    16.619   16.235   65.9    3.2    79   52.1 
2025-09-24 00:00 UT   16 14 50.5   +22 31 08    16.633   16.240   65.3    3.2    79   52.1 
2025-09-25 00:00 UT   16 14 58.1   +22 29 05    16.648   16.244   64.7    3.2    78   52.1 

    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.