P/2017 Y3 (Leonard)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	4 Feb 2018	18.8	1.278 AU	1.507 AU	17h27m	-02°07'	57.2°	40.4°	288°
Perihelion	6 Feb 2018	18.8	1.278 AU	1.507 AU	17h33m	-01°59'	57.2°	40.4°	287°
Today	14 Mar 2025	34.4	14.614 AU	15.438 AU	01h44m	-10°43'	32.9°	2.1°	102°

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 P/2017 Y3 (Leonard) are:

            e (Eccentricity)                : 0.8695380
            q (Perihelion distance)         : 1.2780300
            i (Inclination)                 : 27.62430
            Ω (Longitude of ascending node) : 154.00500
            ω (Argument of perihelion)      : 67.35320
            L (Longitude of perihelion)     : 218.78937
            B (Latitude of perihelion)      : 25.33569
            T (Time of perihelion passage)  : 2458155.85850
            P (Orbital period in years)     : 30.66

            Epoch                           : 2025 Mar 13
            Reference                       : MPC111770

            Classification(s):              : Nearly isotropic; Returning (a < 10000 AU); Halley type (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 (16.50 + 5 log[∆] + 10.00 log[r]), whereas the red curve is being recalculated every 6 hours based on the available COBS/MPC observations (currently 16.85 + 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
2025-03-14 00:00 UT   01 44 54.5   -10 43 55    15.435   14.613   33.1    2.1   102   34.4 
2025-03-14 07:18 UT   01 44 58.6   -10 43 20    15.438   14.614   32.9    2.1   102   34.4 
2025-03-15 00:00 UT   01 45 08.2   -10 42 02    15.445   14.615   32.4    2.1   103   34.4 
2025-03-16 00:00 UT   01 45 22.0   -10 40 09    15.455   14.618   31.7    2.0   104   34.4 
2025-03-17 00:00 UT   01 45 35.9   -10 38 18    15.464   14.621   31.0    2.0   105   34.4 
2025-03-18 00:00 UT   01 45 49.9   -10 36 27    15.474   14.623   30.3    2.0   106   34.4 
2025-03-19 00:00 UT   01 46 04.0   -10 34 36    15.483   14.626   29.6    1.9   108   34.4 
2025-03-20 00:00 UT   01 46 18.3   -10 32 46    15.492   14.629   29.0    1.9   109   34.4 
2025-03-21 00:00 UT   01 46 32.6   -10 30 57    15.500   14.631   28.3    1.8   110   34.5 
2025-03-22 00:00 UT   01 46 47.1   -10 29 09    15.509   14.634   27.7    1.8   112   34.5 
2025-03-23 00:00 UT   01 47 01.6   -10 27 21    15.517   14.636   27.1    1.8   113   34.5 
2025-03-24 00:00 UT   01 47 16.3   -10 25 34    15.525   14.639   26.5    1.7   115   34.5 

    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.