Latest image

Comet 21P/Giacobini-Zinner
True color image of periodic comet 21P/Giacobini-Zinner, obtained on 2018 Aug. 23 (2h04-2h38UT) with 15-cm, f/6 Maksutov-Cassegrain and Canon EOS 6D DSLR. Exposure time was 12x120s at ISO3200.
Copyright © 2018 by H. Mikuz, Črni Vrh Observatory.

Welcome to COBS!

Comet Observation database (COBS) saw first light in 2010 and is maintained by Crni Vrh Observatory. It is a free and unique service for comet observers worldwide which allows submission, display and analysis of comet data in a single location.

Amateur astronomers can make valuable contributions to comet science by observing comets and submitting their observations to COBS as professional astronomers typically do not have telescope time required to acquire regular observations. We therefore encourage comet observers worldwide to submit their observations and contribute to the COBS database.

Registered observers may submit observations using a web based form which which stores the observations in an SQL database and stores them in ICQ format. Observations may be queried and plotted in the web site or exported for further processing, analysis and publication. The database currently contains more than 235000 comet observations of more than 1200 different comets and represents the largest available database of comet observations.

The data stored in COBS is freely available to everyone who honors our data usage policy. Please cite COBS as the reference if you use it for comet studies.

Latest lightcurve

Light-curve of 21P/Giacobini-Zinner (Sep 22, 2018).

Type  Comet name  Obs date       Mag   App  T  Pow   Dia   DC  Tail PA  Observer
  V    21         2018 09 21.10   8.6   10.0B   25    5    5/  0.7  289 CER01
  V    21         2018 09 21.08   8.3   18.5L   73    4.5  4/  14.0m283 KWI  
  C    21         2018 09 21.06   7.7    1.0R a 60    9.5  4/  26.0m274 NOV01
  V    64         2018 09 20.98 [12.1   15.0L  115                      NOV01
  V    21         2018 09 20.83   8.0    8.0B   20    4    4            CAM03
  V    21         2018 09 20.08   7.8   19.8L   37    6.5  4   21.0m281 HAR11
  V    21         2018 09 20.08   8.1   18.5L   73    4.5  4   14.0m280 KWI  
  V    21         2018 09 19.87   8.3   20.0L   90    4    5            PEA  
  V    21         2018 09 19.82   7.8    8.0B   20    4    5            CAM03
  V    46         2018 09 19.81  13.3   41.0L  200    0.8  3            PEA  
  C    38         2018 09 19.42  11.5   10.6R a300    6.2       3.6m254 RAMaa
  C    21         2018 09 19.42   7.0   10.6R a180   20      > 80.0m280 RAMaa
  C    46         2018 09 19.41  11.9   10.6R a300    6.9               RAMaa
  V    21         2018 09 19.32   7.4    8.0R   19    5    5            SOU01
  V    21         2018 09 19.26   7.3    7.0B   15    5    6            SOU01

Comet Observing Planner

Start session:
End session:
Limiting mag:
Min altitude:
Min Solar Elongation:
Min Lunar Elongation:

Current comet magnitudes and observable region

Comet                               Mag   Trend   Observable          When visible
                                                                  45N              45S
21P/Giacobini-Zinner                 8.0  bright  90N to 25S  All night        Never up        
C/2016 M1 (PANSTARRS)                9.0  fade    33N to 90S  Never up         Never up        
C/2017 T3 (ATLAS)                    9.5  fade    61N to 90S  Early evening    Evening         
C/2018 N1 (NEOWISE)                 11.0  fade    75N to 90S  Evening          Best evening    
C/2016 R2 (PANSTARRS)               12.0  fade    90N to 38S  All night        Never up        
C/2016 N6 (PANSTARRS)               12.5  steady  90N to 66S  Poor elongation  Poor elongation 
48P/Johnson                         12.5  steady  66N to 90S  Best morning     Best morning    
P/2013 R3-A (Catalina-PANSTARRS)    13.0  steady  72N to 90S  Best morning     Best morning    
P/2013 R3-B (Catalina-PANSTARRS)    13.0  steady  72N to 90S  Best morning     Best morning    
364P/PANSTARRS                      13.5  fade    55N to 90S  Early evening    Best morning    
38P/Stephan-Oterma                  13.5  bright  90N to 85S  Early evening    Early evening   
29P/Schwassmann-Wachmann            14.0  steady  90N to 88S  Best morning     Best morning    
37P/Forbes                          14.0  fade    90N to 84S  Best morning     Best morning    
C/2017 M4 (ATLAS)                   14.0  steady  90N to 62S  Best evening     Evening         
66P/du Toit                         14.0  fade    75N to 90S  Best morning     Best morning    
P/2010 H2 (Vales)                   14.0  fade    67N to 90S  Evening          Best evening    

The observable region is an approximate indication of the latitude at which the comet may be seen. The period when visible is calculated for latitude 45°N and 45°S.

Latest news

Sep. 10, 2018

The Comet Observation Database - Observer tools and case study (EPSC2018-644, Berlin 2018)

This paper introduces the main functionality of the COBS database [1, 2] that is of interest to a comet observer, with application to C/2004 R2 (Machholz).


Sep. 10, 2018

The Comet Observation Database - Structure and content (EPSC 2018-632, Berlin 2018)

The Comet Observation Database (COBS) [1, 2] is a unique web service that enables comet observers to submit, display and analyse comet data in a single location. The service currently represents one of the largest databases of comet observations (containing more than 235,000 observations) and is available to comet observers worldwide.


Sep. 09, 2018

Green comet makes closest approach to earth

On Sept. 10th, Comet 21P/Giacobini-Zinner ("21P" for short) will make its closest approach to Earth in 72 years--only 58 million km from our planet. This small but active comet is easy to see in small telescopes and binoculars as it shines like a 7th magnitude star. Michael Jäger of Weißenkirchen, Austria, sends this photo of 21P passing through the stars of Auriga on Sept. 7th.


Aug. 25, 2018

A Green Comet Approaches Earth

Comet 21P/Giacobini-Zinner is approaching Earth. On Sept. 10th, it will be 0.39 AU (58 million km) from our planet and almost bright enough to see with the naked eye. Already it is an easy target for backyard telescopes.


Aug. 10, 2018

The cautionary tail of Comet Swift–Tuttle

Comet Swift–Tuttle, formally 109P/Swift–Tuttle, is an enormous, icy comet on a 133 year orbit around the Sun, and the reason for the spectacular annual Perseids meteor showers on Earth.