C/2018 K1 (Weiland)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	8 Apr 2018	18.4	1.880 AU	2.218 AU	21h43m	-21°41'	57.5°	26.7°	246°
Nearest approach	9 Jun 2018	17.0	2.025 AU	1.017 AU	17h51m	-25°09'	170.0°	5.0°	281°
Today	28 Dec 2025	32.9	18.567 AU	17.946 AU	10h21m	+26°14'	127.9°	2.4°	280°

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 13.9 + 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/2018 K1 (Weiland) are:

    e (Eccentricity)                : 0.9378170
    q (Perihelion distance)         : 1.8796280
    i (Inclination)                 : 164.18610
    Ω (Longitude of ascending node) : 260.20330
    ω (Argument of perihelion)      : 325.25290
    L (Longitude of perihelion)     : 293.92230
    B (Latitude of perihelion)      : -8.93539
    T (Time of perihelion passage)  : 2458216.66380
    P (Orbital period in years)     : 166.19

    Epoch                           : 2023 Apr 14
    Reference                       : MPC114602

    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
2025-12-27 00:00 UT   10 21 48.1   +26 11 49    17.963   18.559  126.0    2.5   281   32.9 
2025-12-28 00:00 UT   10 21 39.0   +26 13 19    17.954   18.563  127.0    2.4   280   32.9 
2025-12-28 20:14 UT   10 21 31.3   +26 14 35    17.946   18.567  127.9    2.4   280   32.9 
2025-12-29 00:00 UT   10 21 29.8   +26 14 50    17.945   18.568  128.0    2.4   280   32.9 
2025-12-30 00:00 UT   10 21 20.3   +26 16 21    17.936   18.572  129.0    2.4   279   32.9 
2025-12-31 00:00 UT   10 21 10.7   +26 17 52    17.928   18.576  130.0    2.3   279   32.9 
2026-01-01 00:00 UT   10 21 00.8   +26 19 24    17.920   18.581  131.0    2.3   279   32.9 
2026-01-02 00:00 UT   10 20 50.7   +26 20 57    17.912   18.585  132.0    2.3   278   32.9 
2026-01-03 00:00 UT   10 20 40.4   +26 22 30    17.904   18.589  133.0    2.2   277   32.9 
2026-01-04 00:00 UT   10 20 29.9   +26 24 03    17.896   18.594  134.0    2.2   277   32.9 
2026-01-05 00:00 UT   10 20 19.2   +26 25 37    17.889   18.598  135.0    2.1   276   32.9 
2026-01-06 00:00 UT   10 20 08.3   +26 27 11    17.882   18.602  136.0    2.1   276   32.9 
2026-01-07 00:00 UT   10 19 57.2   +26 28 45    17.875   18.607  137.0    2.1   275   32.9 

    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.