P/2017 Y3 (Leonard)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	4 Feb 2018	18.8	1.278 AU	1.506 AU	17h27m	-02°07'	57.2°	40.5°	288°
Perihelion	6 Feb 2018	18.8	1.277 AU	1.506 AU	17h33m	-01°59'	57.2°	40.5°	287°
Today	25 Apr 2025	34.5	14.724 AU	15.643 AU	01h55m	-09°36'	23.3°	1.5°	190°

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)                : 0.8695840
            q (Perihelion distance)         : 1.2774760
            i (Inclination)                 : 27.62720
            Ω (Longitude of ascending node) : 154.01290
            ω (Argument of perihelion)      : 67.34060
            L (Longitude of perihelion)     : 218.78302
            B (Latitude of perihelion)      : 25.33582
            T (Time of perihelion passage)  : 2458155.88300
            P (Orbital period in years)     : 30.66

            Epoch                           : 2025 Apr 24
            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
2025-04-25 00:00 UT   01 55 34.5   -09 37 41    15.643   14.723   23.0    1.5   189   34.5 
2025-04-25 15:43 UT   01 55 44.9   -09 36 56    15.643   14.724   23.3    1.5   190   34.5 
2025-04-26 00:00 UT   01 55 50.4   -09 36 32    15.643   14.725   23.4    1.6   191   34.5 
2025-04-27 00:00 UT   01 56 06.2   -09 35 24    15.642   14.728   23.9    1.6   193   34.5 
2025-04-28 00:00 UT   01 56 22.1   -09 34 18    15.641   14.730   24.4    1.6   195   34.5 
2025-04-29 00:00 UT   01 56 37.9   -09 33 13    15.640   14.733   24.9    1.7   196   34.5 
2025-04-30 00:00 UT   01 56 53.6   -09 32 10    15.639   14.736   25.5    1.7   198   34.5 
2025-05-01 00:00 UT   01 57 09.4   -09 31 09    15.637   14.738   26.0    1.7   200   34.5 
2025-05-02 00:00 UT   01 57 25.1   -09 30 09    15.635   14.741   26.6    1.8   201   34.5 
2025-05-03 00:00 UT   01 57 40.7   -09 29 10    15.633   14.743   27.2    1.8   203   34.5 
2025-05-04 00:00 UT   01 57 56.3   -09 28 13    15.630   14.746   27.8    1.8   204   34.5 
2025-05-05 00:00 UT   01 58 11.9   -09 27 18    15.628   14.749   28.4    1.9   206   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.