Comet C/2017 O1 (ASASSN1)
True color image of comet C/2017 O1 (ASASSN1), obtained on 2017 Sep. 22 (3h06-3h09UT) with 60-cm, f/3.3 Deltagraph. Exposure time was 60s in each filter.
Copyright © 2017 by H. Mikuz, Črni Vrh Observatory.

Welcome to COBS!

Comet Observation database (COBS) was developed in 2010 and is maintained by Crni Vrh Observatory. It is a unique service offering comet observers to submit, display and analyse comet data in a single location and is opened to comet observers worldwide. Registered observers may submit the observations using a simple web-based form which will store their observations into an SQL database and display them in ICQ format.

Data stored in COBS database is freely available to everyone with respect to our data usage policy, and can be analysed with COBS online tools or exported and further used in other analysis software and publications.

Database currently contains more than 231000 comet observations of more than 1200 different comets and represents the largest available database of comet observations.

Amateur comet observers can make a useful contribution to science by observing comets and submitting their observations to the COBS, as the professional astronomers do not have the time nor the telescopes needed to gather such data. We encourage comet observers worldwide to submit their observations and contribute to the COBS database.

Light-curve of C/2017 O1 (ASASSN1) (Oct 23, 2017).

Recent observations

Type  Comet name  Obs date       Mag     Dia   DC  Tail     Observer
  V      2017O1   2017 10 22.87   9.4     6    2/           WAR01
  V      2017O1   2017 10 22.84  10.1     4.2  3            COLac
  C   217         2017 10 22.32  14.8     1.1       2.0m269 MAS01
  C      2017T1   2017 10 21.74  17.8     0.2  4            BUIaa
  V      2017O1   2017 10 21.23 [ 9.9                       AGUaa
  C      2015ER61 2017 10 21.13  12.5     0.9               HILaa
  C   174         2017 10 21.10  16.8     0.2               HILaa
  C   355         2017 10 21.07  14.3     0.7               HILaa
  C   240         2017 10 20.01  14.3     1.2       0.8m 11 MAS01
  V    29         2017 10 19.46  12.0     3.7  1            WYA  
  V      2015V2   2017 10 19.45  12.2     1.7  2            WYA  
  V    71         2017 10 19.45  13.1     1.5  2/           WYA  
  V      2017O1   2017 10 19.27 [ 9.7                       AGUaa
  C    95         2017 10 18.98  18.0     0.2               HILaa
  V      2017O1   2017 10 18.95   8.9     6    2/           KWI  


Comet Observing Planner

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Current comet magnitudes (October 17)

Comet                     Magnitude   Trend    Observable     When visible
ASASSN (2017 O1)               8.5    steady   80 N to 40 S   best morning
24P/Schaumasse                11      bright   65 N to 15 S   morning
Johnson (2015 V2)             11      fade      5 N to 70 S   evening
PanSTARRS (2015 ER61)         12      fade     80 N to 45 S   best morning
71P/Clark                     12      fade     25 N to 70 S   evening
217P/LINEAR                   13      fade     65 N to 40 S   morning
29P/Schwassmann-Wachmann      13 ?    varies   50 N to 70 S   early evening
PanSTARRS (2016 R2)           13.5    bright   70 N to 65 S   morning
Lemmon-Yeung-PanS (2015 VL62) 13.5    steady   50 N to 65 S   early evening
62P/Tsuchinshan               14      bright   70 N to 20 S   morning
PanSTARRS (2015 O1)           14      steady   65 N to 10 S   evening

List of comets maintained by Jonathan Shanklin at

Latest news

Oct. 03, 2017

ALMA and Rosetta detect Freon-40 in space

Observations made with the Atacama Large Millimeter/submillimeter Array (ALMA) and ESA's Rosetta mission, have revealed the presence of the organohalogen Freon-40 in gas around both an infant star and a comet. Organohalogens are formed by organic processes on Earth, but this is the first ever detection of them in interstellar space. This discovery suggests that organohalogens may not be as good markers of life as had been hoped, but that they may be significant components of the material from which planets form.


Oct. 02, 2017

Unexpected surprise: A final image from Rosetta

Scientists analysing the final telemetry sent by Rosetta immediately before it shut down on the surface of the comet last year have reconstructed one last image of its touchdown site.


Sep. 29, 2017

Farthest active inbound comet yet seen

NASA's Hubble Space Telescope has photographed the farthest active inbound comet ever seen, at a whopping distance of 1.5 billion miles from the Sun (beyond Saturn's orbit). Slightly warmed by the remote Sun, it has already begun to develop an 80,000-mile-wide fuzzy cloud of dust, called a coma, enveloping a tiny, solid nucleus of frozen gas and dust. These observations represent the earliest signs of activity ever seen from a comet entering the solar system's planetary zone for the first time.


Sep. 21, 2017

Unique type of object discovered in our solar system

Astronomers have observed the intriguing characteristics of an unusual type of object in the asteroid belt between Mars and Jupiter: two asteroids orbiting each other and exhibiting comet-like features, including a bright coma and a long tail. This is the first known binary asteroid also classified as a comet.


Sep. 15, 2017

The return of the comet-like exoplanet

Astronomers have focused the Hubble Space Telescope on an exoplanet that had already been seen losing its atmosphere, which forms an enormous cloud of hydrogen, giving the planet the appearance of a giant comet. During earlier observations, it was not possible to cover the whole cloud, whose shape was predicted by numerical simulations. Thanks to these new observations, the scientists have finally been able to confirm the initial predictions.