C/2020 S3 (Erasmus)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Nearest approach	17 Nov 2020	7.5	0.726 AU	1.033 AU	12h33m	-18°47'	42.0°	65.7°	278°
Perihelion	11 Dec 2020	5.2	0.391 AU	1.285 AU	16h19m	-22°28'	12.8°	33.8°	275°
Today	17 Apr 2026	28.0	16.596 AU	17.572 AU	00h50m	+14°40'	12.9°	0.8°	288°

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 8.9 + 5 log[∆] + 10.5 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/2020 S3 (Erasmus) are:

    e (Eccentricity)                : 0.9972150
    q (Perihelion distance)         : 0.3905530
    i (Inclination)                 : 20.11070
    Ω (Longitude of ascending node) : 222.45070
    ω (Argument of perihelion)      : 350.06120
    L (Longitude of perihelion)     : 213.10684
    B (Latitude of perihelion)      : -3.40219
    T (Time of perihelion passage)  : 2459194.94900
    P (Orbital period in years)     : 1660.67

    Epoch                           : 2026 Mar 16
    Reference                       : MPEC 2026-E44

    Classification(s):              : Nearly isotropic; Returning (a < 10000 AU); External (P > 200 years)

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-04-16 00:00 UT   00 50 29.2   +14 38 11    17.567   16.587   11.9    0.7   292   28.0 
2026-04-17 00:00 UT   00 50 42.4   +14 39 34    17.570   16.593   12.5    0.8   289   28.0 
2026-04-17 13:42 UT   00 50 50.0   +14 40 22    17.572   16.596   12.9    0.8   288   28.0 
2026-04-18 00:00 UT   00 50 55.6   +14 40 58    17.574   16.598   13.2    0.8   286   28.0 
2026-04-19 00:00 UT   00 51 08.7   +14 42 21    17.576   16.604   13.9    0.8   284   28.0 
2026-04-20 00:00 UT   00 51 21.8   +14 43 45    17.579   16.610   14.7    0.9   282   28.0 
2026-04-21 00:00 UT   00 51 34.8   +14 45 09    17.581   16.616   15.4    0.9   280   28.0 
2026-04-22 00:00 UT   00 51 47.7   +14 46 33    17.583   16.621   16.2    1.0   278   28.0 
2026-04-23 00:00 UT   00 52 00.5   +14 47 57    17.585   16.627   17.0    1.0   276   28.0 
2026-04-24 00:00 UT   00 52 13.3   +14 49 21    17.587   16.633   17.8    1.1   275   28.0 
2026-04-25 00:00 UT   00 52 26.0   +14 50 45    17.588   16.638   18.6    1.1   273   28.0 
2026-04-26 00:00 UT   00 52 38.7   +14 52 09    17.589   16.644   19.4    1.2   272   28.0 
2026-04-27 00:00 UT   00 52 51.3   +14 53 33    17.590   16.650   20.2    1.2   271   28.0 

    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.