C/2017 M4 (ATLAS)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	17 Jan 2019	14.0	3.230 AU	3.954 AU	17h19m	-13°08'	37.5°	10.7°	287°
Nearest approach	13 May 2019	13.3	3.416 AU	2.465 AU	15h59m	-40°13'	156.6°	6.8°	336°
Today	14 Oct 2026	26.8	19.284 AU	19.134 AU	06h18m	-34°44'	97.2°	2.9°	285°

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 4.8 + 5 log[∆] + 12.1 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/2017 M4 (ATLAS) are:

    e (Eccentricity)                : 0.9997530
    q (Perihelion distance)         : 3.2297060
    i (Inclination)                 : 105.65830
    Ω (Longitude of ascending node) : 65.94990
    ω (Argument of perihelion)      : 167.31120
    L (Longitude of perihelion)     : 69.42744
    B (Latitude of perihelion)      : 12.21049
    T (Time of perihelion passage)  : 2458500.59430

    Epoch                           : 2026 Oct 13
    Reference                       : MPC194152

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-10-13 00:00 UT   06 18 47.0   -34 41 12    19.140   19.276   96.3    2.9   284   26.8 
2026-10-14 00:00 UT   06 18 41.5   -34 43 21    19.136   19.281   96.9    2.9   285   26.8 
2026-10-14 14:26 UT   06 18 38.0   -34 44 38    19.134   19.284   97.2    2.9   285   26.8 
2026-10-15 00:00 UT   06 18 35.7   -34 45 29    19.132   19.286   97.4    2.9   285   26.8 
2026-10-16 00:00 UT   06 18 29.7   -34 47 36    19.129   19.291   97.9    2.9   286   26.8 
2026-10-17 00:00 UT   06 18 23.4   -34 49 43    19.125   19.296   98.4    2.9   287   26.8 
2026-10-18 00:00 UT   06 18 16.9   -34 51 48    19.121   19.301   98.9    2.9   288   26.8 
2026-10-19 00:00 UT   06 18 10.1   -34 53 52    19.117   19.307   99.5    2.9   289   26.8 
2026-10-20 00:00 UT   06 18 03.1   -34 55 56    19.114   19.312  100.0    2.9   290   26.8 
2026-10-21 00:00 UT   06 17 55.8   -34 57 58    19.110   19.317  100.5    2.9   291   26.8 
2026-10-22 00:00 UT   06 17 48.2   -34 59 59    19.107   19.322  101.0    2.9   292   26.8 
2026-10-23 00:00 UT   06 17 40.4   -35 01 59    19.103   19.327  101.5    2.9   293   26.8 
2026-10-24 00:00 UT   06 17 32.4   -35 03 58    19.100   19.332  102.0    2.9   294   26.8 

    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.