C/2017 F1 (Lemmon)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	27 Nov 2017	20.0	4.502 AU	3.845 AU	07h52m	+57°27'	126.4°	10.2°	251°
Nearest approach	23 Dec 2017	19.9	4.507 AU	3.698 AU	06h31m	+62°05'	141.1°	7.9°	189°
Today	26 Apr 2024	28.7	16.104 AU	16.661 AU	22h50m	-07°50'	54.9°	2.9°	247°

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 F1 (Lemmon) are:

            e (Eccentricity)                : 1.0012160
            q (Perihelion distance)         : 4.5015920
            i (Inclination)                 : 146.47230
            Ω (Longitude of ascending node) : 158.78580
            ω (Argument of perihelion)      : 64.72580
            L (Longitude of perihelion)     : 98.31225
            B (Latitude of perihelion)      : 29.96476
            T (Time of perihelion passage)  : 2458085.11840

            Epoch                           : 2023 Jan 31
            Reference                       : MPC111769

            Classification(s):              : Nearly isotropic; New (a > 10000 AU)
        

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 light curve is based on the absolute magnitude and slope parameter as calculated from an MPEC, or the latest values provided by the minor planet center. (10.50 + 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
2024-04-26 00:00 UT   22 50 38.1   -07 50 39    16.661   16.104   54.9    2.9   247   28.7 
2024-04-26 00:39 UT   22 50 38.2   -07 50 38    16.661   16.104   54.9    2.9   247   28.7 
2024-04-27 00:00 UT   22 50 44.1   -07 50 27    16.652   16.109   55.8    3.0   247   28.7 
2024-04-28 00:00 UT   22 50 49.9   -07 50 17    16.643   16.114   56.8    3.0   247   28.7 
2024-04-29 00:00 UT   22 50 55.5   -07 50 08    16.634   16.120   57.7    3.0   247   28.7 
2024-04-30 00:00 UT   22 51 01.0   -07 50 00    16.625   16.125   58.7    3.1   247   28.7 
2024-05-01 00:00 UT   22 51 06.2   -07 49 53    16.615   16.130   59.6    3.1   247   28.7 
2024-05-02 00:00 UT   22 51 11.3   -07 49 48    16.605   16.135   60.6    3.1   247   28.7 
2024-05-03 00:00 UT   22 51 16.2   -07 49 44    16.596   16.140   61.5    3.1   247   28.7 
2024-05-04 00:00 UT   22 51 20.9   -07 49 40    16.586   16.145   62.5    3.2   247   28.7 
2024-05-05 00:00 UT   22 51 25.4   -07 49 38    16.576   16.151   63.5    3.2   247   28.7 
2024-05-06 00:00 UT   22 51 29.7   -07 49 38    16.565   16.156   64.4    3.2   247   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.