C/2021 U5 (Catalina)
ephemeris	date	magn	radius	delta	ra	dec	elong	phase	PA
Perihelion	27 Jan 2022	17.8	2.360 AU	1.622 AU	10h19m	-27°12'	128.1°	19.2°	329°
Nearest approach	3 Mar 2022	17.6	2.393 AU	1.461 AU	10h15m	-16°58'	154.2°	10.4°	24°
Today	18 Jul 2026	29.7	13.187 AU	12.463 AU	18h10m	+18°20'	133.8°	3.2°	147°

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. (13.0 + 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/2021 U5 (Catalina) are:

    e (Eccentricity)                : 0.9896440
    q (Perihelion distance)         : 2.3597390
    i (Inclination)                 : 39.03940
    Ω (Longitude of ascending node) : 182.61560
    ω (Argument of perihelion)      : 321.53100
    L (Longitude of perihelion)     : 150.93522
    B (Latitude of perihelion)      : -23.06823
    T (Time of perihelion passage)  : 2459606.78800
    P (Orbital period in years)     : 3439.60

    Epoch                           : 2026 May 29
    Reference                       : MPC194177

    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
2026-07-17 00:00 UT   18 10 24.9   +18 22 13    12.451   13.180  134.2    3.2   149   29.7 
2026-07-18 00:00 UT   18 10 10.2   +18 20 54    12.461   13.186  133.8    3.2   148   29.7 
2026-07-18 04:19 UT   18 10 07.6   +18 20 40    12.463   13.187  133.8    3.2   147   29.7 
2026-07-19 00:00 UT   18 09 55.7   +18 19 33    12.472   13.192  133.4    3.2   146   29.7 
2026-07-20 00:00 UT   18 09 41.3   +18 18 09    12.483   13.198  133.0    3.2   145   29.7 
2026-07-21 00:00 UT   18 09 27.1   +18 16 42    12.494   13.204  132.6    3.2   144   29.7 
2026-07-22 00:00 UT   18 09 13.0   +18 15 12    12.506   13.210  132.2    3.3   143   29.7 
2026-07-23 00:00 UT   18 08 59.2   +18 13 40    12.517   13.216  131.8    3.3   141   29.7 
2026-07-24 00:00 UT   18 08 45.5   +18 12 05    12.529   13.222  131.3    3.3   140   29.7 
2026-07-25 00:00 UT   18 08 32.0   +18 10 28    12.541   13.228  130.8    3.3   139   29.7 
2026-07-26 00:00 UT   18 08 18.7   +18 08 48    12.553   13.234  130.4    3.4   138   29.7 
2026-07-27 00:00 UT   18 08 05.6   +18 07 05    12.565   13.240  129.9    3.4   137   29.7 
2026-07-28 00:00 UT   18 07 52.7   +18 05 20    12.578   13.246  129.4    3.4   136   29.7 

    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.