C/2018 K1 (Weiland)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	9 Apr 2018	18.3	1.860 AU	2.187 AU	21h46m	-21°31'	57.9°	27.1°	246°
Nearest approach	9 Jun 2018	16.9	2.004 AU	0.996 AU	17h52m	-25°15'	170.0°	5.0°	281°
Today	18 Sep 2026	33.4	19.689 AU	20.531 AU	10h10m	+25°53'	32.3°	1.6°	314°

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)                : 0.9380720
    q (Perihelion distance)         : 1.8597350
    i (Inclination)                 : 164.18280
    Ω (Longitude of ascending node) : 260.24880
    ω (Argument of perihelion)      : 325.06250
    L (Longitude of perihelion)     : 294.15512
    B (Latitude of perihelion)      : -8.98034
    T (Time of perihelion passage)  : 2458217.80370
    P (Orbital period in years)     : 164.57

    Epoch                           : 2026 May 29
    Reference                       : MPC194156

    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
2026-09-17 00:00 UT   10 10 04.1   +25 53 51    20.536   19.685   31.4    1.5   315   33.4 
2026-09-18 00:00 UT   10 10 13.7   +25 53 21    20.532   19.689   32.2    1.6   314   33.4 
2026-09-18 01:03 UT   10 10 14.1   +25 53 20    20.531   19.689   32.3    1.6   314   33.4 
2026-09-19 00:00 UT   10 10 23.2   +25 52 52    20.527   19.693   33.1    1.6   313   33.4 
2026-09-20 00:00 UT   10 10 32.6   +25 52 24    20.522   19.698   33.9    1.6   312   33.4 
2026-09-21 00:00 UT   10 10 41.9   +25 51 57    20.518   19.702   34.8    1.7   312   33.4 
2026-09-22 00:00 UT   10 10 51.2   +25 51 31    20.512   19.706   35.7    1.7   311   33.4 
2026-09-23 00:00 UT   10 11 00.3   +25 51 06    20.507   19.710   36.5    1.7   311   33.4 
2026-09-24 00:00 UT   10 11 09.3   +25 50 42    20.502   19.714   37.4    1.8   310   33.4 
2026-09-25 00:00 UT   10 11 18.3   +25 50 19    20.496   19.719   38.3    1.8   309   33.4 
2026-09-26 00:00 UT   10 11 27.1   +25 49 57    20.490   19.723   39.1    1.8   309   33.4 
2026-09-27 00:00 UT   10 11 35.9   +25 49 37    20.484   19.727   40.0    1.9   308   33.4 
2026-09-28 00:00 UT   10 11 44.5   +25 49 18    20.477   19.731   40.9    1.9   308   33.4 

    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.