C/2025 D1 (Groeller)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Today	16 Sep 2025	18.9	14.807 AU	15.529 AU	09h28m	+33°51'	42.8°	2.6°	310°
Nearest approach	3 Feb 2028	18.3	14.126 AU	13.143 AU	08h58m	+13°41'	176.6°	0.2°	32°
Perihelion	20 May 2028	18.5	14.118 AU	14.432 AU	08h41m	+12°18'	70.0°	3.9°	107°

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/2025 D1 (Groeller) are:

            e (Eccentricity)                : 1.0029880
            q (Perihelion distance)         : 14.1179910
            i (Inclination)                 : 84.45860
            Ω (Longitude of ascending node) : 312.90070
            ω (Argument of perihelion)      : 185.90800
            L (Longitude of perihelion)     : 313.47322
            B (Latitude of perihelion)      : -5.88029
            T (Time of perihelion passage)  : 2461912.10920

            Epoch                           : 2025 Sep 15
            Reference                       : MPC185660

            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. (1.20 + 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
2025-09-16 00:00 UT   09 28 46.3   +33 51 58    15.530   14.807   42.7    2.6   310   18.9 
2025-09-16 02:09 UT   09 28 47.4   +33 51 49    15.529   14.807   42.8    2.6   310   18.9 
2025-09-17 00:00 UT   09 28 59.0   +33 50 24    15.518   14.806   43.5    2.7   309   18.9 
2025-09-18 00:00 UT   09 29 11.5   +33 48 52    15.506   14.804   44.4    2.7   309   18.9 
2025-09-19 00:00 UT   09 29 23.9   +33 47 21    15.494   14.803   45.2    2.8   308   18.9 
2025-09-20 00:00 UT   09 29 36.1   +33 45 52    15.481   14.802   46.0    2.8   308   18.9 
2025-09-21 00:00 UT   09 29 48.2   +33 44 24    15.469   14.800   46.9    2.8   307   18.8 
2025-09-22 00:00 UT   09 30 00.0   +33 42 58    15.456   14.799   47.7    2.9   306   18.8 
2025-09-23 00:00 UT   09 30 11.7   +33 41 33    15.443   14.797   48.5    2.9   306   18.8 
2025-09-24 00:00 UT   09 30 23.3   +33 40 10    15.430   14.796   49.4    3.0   305   18.8 
2025-09-25 00:00 UT   09 30 34.6   +33 38 48    15.416   14.795   50.2    3.0   305   18.8 
2025-09-26 00:00 UT   09 30 45.8   +33 37 28    15.403   14.793   51.1    3.0   305   18.8 

    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.