C/2018 Y1 (Iwamoto)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	2 Feb 2019	7.4	1.299 AU	0.444 AU	12h21m	-04°36'	126.4°	37.6°	295°
Nearest approach	10 Feb 2019	6.7	1.305 AU	0.320 AU	09h58m	+20°08'	172.0°	6.1°	225°
Today	24 Sep 2026	34.4	20.206 AU	19.221 AU	23h28m	+07°44'	168.6°	0.6°	129°

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 7.4 + 5 log[∆] + 15.8 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 Y1 (Iwamoto) are:

    e (Eccentricity)                : 0.9897730
    q (Perihelion distance)         : 1.2992730
    i (Inclination)                 : 160.50890
    Ω (Longitude of ascending node) : 147.28770
    ω (Argument of perihelion)      : 357.89670
    L (Longitude of perihelion)     : 149.27057
    B (Latitude of perihelion)      : -0.70165
    T (Time of perihelion passage)  : 2458517.24240
    P (Orbital period in years)     : 1431.95

    Epoch                           : 2026 May 29
    Reference                       : MPC194158

    Classification(s):              : Nearly isotropic; Returning (a < 10000 AU); External (P > 200 years)

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-09-23 00:00 UT   23 28 60.0   +07 46 12    19.211   20.198  169.2    0.5   137   34.4 
2026-09-24 00:00 UT   23 28 48.0   +07 44 46    19.218   20.203  168.8    0.6   132   34.4 
2026-09-24 11:01 UT   23 28 42.6   +07 44 07    19.221   20.206  168.6    0.6   129   34.4 
2026-09-25 00:00 UT   23 28 36.1   +07 43 20    19.225   20.208  168.3    0.6   127   34.4 
2026-09-26 00:00 UT   23 28 24.3   +07 41 53    19.232   20.213  167.8    0.6   123   34.4 
2026-09-27 00:00 UT   23 28 12.5   +07 40 26    19.239   20.218  167.2    0.6   119   34.4 
2026-09-28 00:00 UT   23 28 00.7   +07 38 59    19.247   20.223  166.6    0.7   115   34.4 
2026-09-29 00:00 UT   23 27 49.0   +07 37 32    19.255   20.228  165.9    0.7   112   34.4 
2026-09-30 00:00 UT   23 27 37.4   +07 36 04    19.263   20.233  165.1    0.7   109   34.4 
2026-10-01 00:00 UT   23 27 25.8   +07 34 36    19.272   20.238  164.4    0.8   106   34.4 
2026-10-02 00:00 UT   23 27 14.3   +07 33 08    19.281   20.243  163.6    0.8   104   34.4 
2026-10-03 00:00 UT   23 27 02.8   +07 31 39    19.290   20.248  162.8    0.8   102   34.4 
2026-10-04 00:00 UT   23 26 51.4   +07 30 11    19.299   20.253  161.9    0.9   100   34.4 

    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.