C/2025 D1 (Groeller)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Today	17 Aug 2026	18.7	14.420 AU	15.393 AU	09h13m	+26°34'	15.5°	1.1°	327°
Nearest approach	3 Feb 2028	18.3	14.124 AU	13.140 AU	08h58m	+13°41'	176.6°	0.2°	32°
Perihelion	23 May 2028	18.5	14.115 AU	14.469 AU	08h42m	+12°14'	67.7°	3.8°	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.)

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. 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. (1.2 + 5 log[∆] + 10.0 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/2025 D1 (Groeller) are:

    e (Eccentricity)                : 1.0031880
    q (Perihelion distance)         : 14.1152500
    i (Inclination)                 : 84.44890
    Ω (Longitude of ascending node) : 312.90350
    ω (Argument of perihelion)      : 185.97590
    L (Longitude of perihelion)     : 313.48366
    B (Latitude of perihelion)      : -5.94777
    T (Time of perihelion passage)  : 2461914.60970

    Epoch                           : 2026 Aug 13
    Reference                       : MPC194194

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-08-16 00:00 UT   09 12 44.7   +26 38 19    15.401   14.422   14.3    1.0   332   18.7 
2026-08-17 00:00 UT   09 12 59.4   +26 35 56    15.397   14.421   14.9    1.0   329   18.7 
2026-08-17 19:09 UT   09 13 11.2   +26 34 02    15.393   14.420   15.5    1.1   327   18.7 
2026-08-18 00:00 UT   09 13 14.1   +26 33 34    15.393   14.420   15.6    1.1   327   18.7 
2026-08-19 00:00 UT   09 13 28.8   +26 31 12    15.388   14.419   16.3    1.1   325   18.7 
2026-08-20 00:00 UT   09 13 43.4   +26 28 51    15.383   14.418   17.0    1.2   323   18.7 
2026-08-21 00:00 UT   09 13 57.9   +26 26 31    15.378   14.417   17.7    1.2   321   18.7 
2026-08-22 00:00 UT   09 14 12.4   +26 24 11    15.372   14.416   18.4    1.3   319   18.7 
2026-08-23 00:00 UT   09 14 26.8   +26 21 52    15.367   14.415   19.2    1.3   318   18.7 
2026-08-24 00:00 UT   09 14 41.2   +26 19 34    15.361   14.414   19.9    1.4   316   18.7 
2026-08-25 00:00 UT   09 14 55.5   +26 17 17    15.355   14.413   20.7    1.4   315   18.7 
2026-08-26 00:00 UT   09 15 09.7   +26 15 00    15.348   14.413   21.5    1.5   314   18.7 
2026-08-27 00:00 UT   09 15 23.9   +26 12 45    15.341   14.412   22.3    1.5   313   18.7 

    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.