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°12'	156.6°	6.8°	336°
Today	12 Aug 2026	26.8	18.962 AU	19.356 AU	06h16m	-32°34'	65.7°	2.8°	231°

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)                : 0.9997980
    q (Perihelion distance)         : 3.2302300
    i (Inclination)                 : 105.65370
    Ω (Longitude of ascending node) : 65.95850
    ω (Argument of perihelion)      : 167.32060
    L (Longitude of perihelion)     : 69.43239
    B (Latitude of perihelion)      : 12.20173
    T (Time of perihelion passage)  : 2458500.66620

    Epoch                           : 2026 Aug 11
    Reference                       : MPC194152

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-08-11 00:00 UT   06 16 20.2   -32 33 21    19.357   18.957   65.3    2.8   230   26.8 
2026-08-12 00:00 UT   06 16 29.1   -32 34 50    19.356   18.962   65.7    2.8   231   26.8 
2026-08-12 00:01 UT   06 16 29.2   -32 34 50    19.356   18.962   65.7    2.8   231   26.8 
2026-08-13 00:00 UT   06 16 37.9   -32 36 21    19.354   18.967   66.1    2.8   232   26.8 
2026-08-14 00:00 UT   06 16 46.5   -32 37 53    19.353   18.972   66.5    2.8   233   26.8 
2026-08-15 00:00 UT   06 16 54.9   -32 39 27    19.351   18.977   66.9    2.8   234   26.8 
2026-08-16 00:00 UT   06 17 03.1   -32 41 03    19.349   18.982   67.3    2.8   235   26.8 
2026-08-17 00:00 UT   06 17 11.2   -32 42 41    19.347   18.987   67.7    2.8   236   26.8 
2026-08-18 00:00 UT   06 17 19.0   -32 44 20    19.345   18.992   68.2    2.8   237   26.8 
2026-08-19 00:00 UT   06 17 26.7   -32 46 01    19.343   18.997   68.6    2.8   237   26.8 
2026-08-20 00:00 UT   06 17 34.2   -32 47 43    19.341   19.003   69.0    2.9   238   26.8 
2026-08-21 00:00 UT   06 17 41.5   -32 49 26    19.339   19.008   69.5    2.9   239   26.8 
2026-08-22 00:00 UT   06 17 48.7   -32 51 12    19.336   19.013   69.9    2.9   240   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.