C/2018 W1 (Catalina)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	14 May 2019	11.2	1.350 AU	1.929 AU	04h22m	-20°17'	41.5°	29.7°	158°
Nearest approach	26 Jun 2019	12.3	1.481 AU	1.673 AU	07h17m	-36°08'	61.2°	37.0°	164°
Today	16 Oct 2025	52.2	16.339 AU	16.926 AU	16h18m	+21°49'	52.5°	2.8°	59°

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. This lightcurve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 5.4 + 5 log[∆] + 33.5 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/2018 W1 (Catalina) are:

    e (Eccentricity)                : 0.9379130
    q (Perihelion distance)         : 1.3503040
    i (Inclination)                 : 83.37860
    Ω (Longitude of ascending node) : 233.61490
    ω (Argument of perihelion)      : 251.15900
    L (Longitude of perihelion)     : 252.28618
    B (Latitude of perihelion)      : -70.06929
    T (Time of perihelion passage)  : 2458617.77440
    P (Orbital period in years)     : 101.43

    Epoch                           : 2025 Oct 15
    Reference                       : MPEC 2021-P47

    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
2025-10-16 00:00 UT   16 18 21.8   +21 50 20    16.922   16.338   52.7    2.8    59   52.2 
2025-10-16 08:12 UT   16 18 25.8   +21 49 48    16.926   16.339   52.5    2.8    59   52.2 
2025-10-17 00:00 UT   16 18 33.5   +21 48 45    16.934   16.342   52.2    2.8    58   52.2 
2025-10-18 00:00 UT   16 18 45.3   +21 47 10    16.945   16.347   51.7    2.7    57   52.3 
2025-10-19 00:00 UT   16 18 57.3   +21 45 38    16.956   16.351   51.2    2.7    56   52.3 
2025-10-20 00:00 UT   16 19 09.4   +21 44 07    16.967   16.356   50.8    2.7    55   52.3 
2025-10-21 00:00 UT   16 19 21.6   +21 42 37    16.978   16.360   50.3    2.7    54   52.3 
2025-10-22 00:00 UT   16 19 34.0   +21 41 10    16.988   16.364   49.9    2.7    53   52.3 
2025-10-23 00:00 UT   16 19 46.6   +21 39 44    16.998   16.369   49.4    2.6    52   52.3 
2025-10-24 00:00 UT   16 19 59.3   +21 38 20    17.009   16.373   49.0    2.6    51   52.3 
2025-10-25 00:00 UT   16 20 12.1   +21 36 57    17.018   16.378   48.6    2.6    50   52.3 
2025-10-26 00:00 UT   16 20 25.0   +21 35 37    17.028   16.382   48.2    2.6    48   52.3 

    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.