38P/Stephan-Oterma
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	14 Nov 2018	6.8	1.582 AU	0.820 AU	07h25m	+21°45'	121.6°	32.2°	278°
Nearest approach	15 Dec 2018	7.0	1.632 AU	0.731 AU	08h10m	+34°48'	143.7°	20.9°	262°
Today	9 Jan 2026	42.6	15.104 AU	15.742 AU	15h59m	-14°14'	48.2°	2.8°	287°

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 1.3 + 5 log[∆] + 30.0 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 38P/Stephan-Oterma are:

    e (Eccentricity)                : 0.8596660
    q (Perihelion distance)         : 1.5816850
    i (Inclination)                 : 18.40920
    Ω (Longitude of ascending node) : 77.86740
    ω (Argument of perihelion)      : 359.61340
    L (Longitude of perihelion)     : 77.50058
    B (Latitude of perihelion)      : -0.12209
    T (Time of perihelion passage)  : 2458436.51820
    P (Orbital period in years)     : 37.84

    Epoch                           : 2026 Jan 08
    Reference                       : MPEC 2025-W75

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

Ephemerides

Date       Time       RA (2000)    DEC (2000)    delta   radius  elong  phase   PA    magn
2026-01-08 00:00 UT   15 59 27.4   -14 13 46    15.754   15.100   47.0    2.7   287   42.6 
2026-01-09 00:00 UT   15 59 39.6   -14 14 11    15.744   15.103   47.9    2.8   287   42.6 
2026-01-09 05:53 UT   15 59 42.6   -14 14 18    15.742   15.104   48.2    2.8   287   42.6 
2026-01-10 00:00 UT   15 59 51.6   -14 14 36    15.735   15.106   48.9    2.8   287   42.6 
2026-01-11 00:00 UT   16 00 03.4   -14 14 60    15.725   15.109   49.8    2.9   287   42.6 
2026-01-12 00:00 UT   16 00 15.1   -14 15 23    15.714   15.112   50.8    2.9   287   42.6 
2026-01-13 00:00 UT   16 00 26.5   -14 15 45    15.704   15.115   51.8    2.9   286   42.6 
2026-01-14 00:00 UT   16 00 37.8   -14 16 06    15.694   15.118   52.7    3.0   286   42.6 
2026-01-15 00:00 UT   16 00 48.8   -14 16 26    15.683   15.122   53.7    3.0   286   42.6 
2026-01-16 00:00 UT   16 00 59.7   -14 16 45    15.672   15.125   54.7    3.0   286   42.6 
2026-01-17 00:00 UT   16 01 10.3   -14 17 03    15.661   15.128   55.6    3.1   286   42.6 
2026-01-18 00:00 UT   16 01 20.8   -14 17 21    15.650   15.131   56.6    3.1   286   42.6 
2026-01-19 00:00 UT   16 01 31.0   -14 17 37    15.638   15.134   57.6    3.1   285   42.6 

    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.