Comet C/2017 O1 (ASASSN1)
Fales color image of comet C/2017 O1 (ASASSN1), obtained on 2017 Aug 16 (2h08-2h14UT) with 60-cm, f/3.3 Deltagraph and CCD. Exposure time was 5x60s.
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) (Sep 18, 2017).

Recent observations

Type  Comet name  Obs date       Mag     Dia   DC  Tail     Observer
  V      2017O1   2017 09 20.02  10.1     3.5  3            COLac
  C    62         2017 09 19.47  13.9     1.3               RAMaa
  C    96         2017 09 19.38  16.5     0.18              RAMaa
  C      2017K2   2017 09 19.17  19.2          5            BUIaa
  C      2015O1   2017 09 19.11  14.2     0.6       1.8m105 RAMaa
  C      2016M1   2017 09 19.11  14.0     0.8               RAMaa
  V      2017O1   2017 09 18.90 [ 8.9   ! 3                 PAR03
  V      2017O1   2017 09 18.87  11.5:         9            GEIaa
  V      2017O1   2017 09 18.39 [ 8.8                       AGUaa
  V      2017O1   2017 09 18.38   9.0     5    1            HER02
  V    62         2017 09 18.08 [14.5   ! 1.3               CER01
  V   217         2017 09 18.05  12.7     1.5  4            CER01
  V      2016R2   2017 09 18.04  13.9     1.7  3            CER01
  C      2015VL62 2017 09 18.03  15.0     0.6               HILaa
  C      2017D2   2017 09 18.02  15.4     0.3               HILaa


Comet Observing Planner

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Current comet magnitudes (August 30)

Comet                     Magnitude   Trend    Observable     When visible
ASASSN (2017 O1)               9      bright   65 N to 65 S   best morning
Johnson (2015 V2)             10      fade     20 N to 85 S   evening
PanSTARRS (2015 ER61)         11.5    fade     65 N to 45 S   best morning
71P/Clark                     12      fade     20 N to 85 S   best evening
217P/LINEAR                   12      fade     55 N to 40 S   early morning
29P/Schwassmann-Wachmann      13 ?    varies   50 N to 80 S   best evening
PanSTARRS (2016 R2)           13.5 ?  bright   55 N to 70 S   early morning
Lemmon-Yeung-PanS (2015 VL62) 13.5    steady   60 N to 60 S   best morning
PanSTARRS (2015 O1)           13.5    steady   60 N to 25 S   evening
24P/Schaumasse                14 ?    bright   35 N to  0 S   early morning

List of comets maintained by Jonathan Shanklin at

Latest news

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.


Sep. 12, 2017

Does the organic material of comets predate our solar system?

The Rosetta space probe discovered a large amount of organic material in the nucleus of comet 'Chury.' Researchers now advance the theory that this matter has its origin in interstellar space and predates the birth of the solar system.


Jul. 26, 2017

Large, distant comets more common than previously thought

There are about seven times more long-period comets measuring at least 1 kilometer across than previously predicted, suggests new research. The researchers also found that long-period comets are, on average, nearly twice as large as 'Jupiter family' comets, whose orbits are shaped by Jupiter's gravity and have periods of less than 20 years.


Jul. 07, 2017

Bizarro comet challenging researchers

Scientists pursue research through observation, experimentation and modeling. They strive for all of these pieces to fit together, but sometimes finding the unexpected is even more exciting. That's what happened recently to a researcher who studies comets, asteroids and planetary formation and was part of a team that published a study focused on the comet 174P/Echeclus. It didn't behave the way the team was expecting.


Jun. 27, 2017

New tool for CCD photometry - tutorial

CCD photometry of comet still remains as a very difficult work, especially for most wanted total coma magnitudes, compatible with visual observations. Also the usual problem is creating of proper ICQ coded line of observation. To help observers with this, I programmed an application - tool for comet observers, which is now in testing - beta phase.