C/2017 O1 (ASASSN)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	16 Oct 2017	10.8	1.491 AU	0.697 AU	04h33m	+51°36'	122.3°	34.4°	240°
Nearest approach	17 Oct 2017	10.8	1.491 AU	0.696 AU	04h35m	+53°25'	122.4°	34.3°	238°
Today	9 May 2024	28.7	18.231 AU	17.396 AU	13h06m	+01°39'	144.8°	1.8°	124°

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/2017 O1 (ASASSN) are:

            e (Eccentricity)                : 0.9961060
            q (Perihelion distance)         : 1.4906670
            i (Inclination)                 : 39.99240
            Ω (Longitude of ascending node) : 25.71300
            ω (Argument of perihelion)      : 20.84740
            L (Longitude of perihelion)     : 41.97765
            B (Latitude of perihelion)      : 13.22168
            T (Time of perihelion passage)  : 2458042.56890
            P (Orbital period in years)     : 7489.92

            Epoch                           : 2022 Nov 15
            Reference                       : MPEC 2022-OB6

            Classification(s):              : Nearly isotropic; Returning (a < 10000 AU); External (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 (11.00 + 5 log[∆] + 10.00 log[r]), whereas the red curve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 9.86 + 5 log[∆] + 10.00 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
2024-05-09 00:00 UT   13 06 28.0   +01 39 12    17.389   18.228  145.3    1.8   124   28.7 
2024-05-09 12:18 UT   13 06 22.9   +01 39 28    17.396   18.231  144.8    1.8   124   28.7 
2024-05-10 00:00 UT   13 06 18.0   +01 39 44    17.403   18.234  144.3    1.9   124   28.7 
2024-05-11 00:00 UT   13 06 08.1   +01 40 15    17.418   18.239  143.4    1.9   124   28.7 
2024-05-12 00:00 UT   13 05 58.3   +01 40 45    17.433   18.245  142.4    1.9   123   28.7 
2024-05-13 00:00 UT   13 05 48.7   +01 41 13    17.449   18.250  141.4    2.0   123   28.7 
2024-05-14 00:00 UT   13 05 39.1   +01 41 41    17.464   18.255  140.4    2.0   122   28.7 
2024-05-15 00:00 UT   13 05 29.8   +01 42 07    17.480   18.261  139.4    2.1   122   28.7 
2024-05-16 00:00 UT   13 05 20.5   +01 42 32    17.496   18.266  138.5    2.1   122   28.7 
2024-05-17 00:00 UT   13 05 11.5   +01 42 56    17.513   18.271  137.5    2.1   121   28.7 
2024-05-18 00:00 UT   13 05 02.5   +01 43 18    17.529   18.277  136.5    2.2   121   28.7 
2024-05-19 00:00 UT   13 04 53.8   +01 43 39    17.546   18.282  135.5    2.2   121   28.7 

    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.