International Comet Quarterly

What Is The International Comet Quarterly?

The International Comet Quarterly (ICQ) is a non-profit scientific journal [ISSN 0736-6922] devoted to the observation, news, and study of comets; it serves as a link between amateur and professional astronomers in the exchange of useful observations (following a standardized format) and news regarding all comets. The ICQ was published at the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, full-time from 1990 until early 2010 (part-time during 1980-1990). Beginning in 2010, it is being published at the Earth and Planetary Sciences Department at Harvard University. The ICQ is the continuation of The Comet, founded in March 1973, and The Comet Quarterly, assuming its present title and format in late 1978 (and published by the Department of Physics and Astronomy at Appalachian State University until 1990). The ICQ is indexed in Astronomy and Astrophysics Abstracts and in Science Abstracts, Section A.

Sample pages and articles from the ICQ are available online here. The October 1996 issue was Number 100 in the publication's series (dating back to 1973), and it contained many pages of observations and images of comets from observers worldwide, plus articles on the history of total visual magnitude methodology; on comets for the visual observer in 1997; on the lives of two well-known comet observers, A. Mrkos and S. K. Vsekhsvyatskii; and an index for the first 23 years of this publication. Coinciding with this "century issue", minor planet (5865) 1984 QQ --- discovered on 1984 Aug. 31 by Antonin Mrkos --- has been named Qualytemocrina (a play on the letters in the ICQ title; cf. Minor Planet Circular 28089).

Example of recent issues: The October 2002 issue contains an article on the apparent disintegration of comet C/2002 O4, an article on comets predicted to be observable visually in 2003, an obituary notice on the comet discoverer Yuji Hyakutake, and descriptive and tabuluated observations of comets; the July 2002 issue contained the first observations of CCD photometry in the new extended format (which provides for inclusion of information on the CCD cameras, software, and other important parameters), and includes numerous CCD images of recent bright comets. [Another example of contents is found in the July 1998 issue, which contained an article on the dust halos of comet C/1995 O1, news on the Edgar Wilson Award, notice of a new catalogue of comet discoveries, and book reviews and a movie review (along with more than 40 pages listing individual observations -- tabulated and descriptive -- of recent comets)]. [12/27/02]

The ICQ publishes the following as its primary functions:
  1. Photometric observations of comets in tabulated format, including carefully-made visual and CCD magnitude estimates of comets with proper documentation; as such, the journal serves to make widely available, in one convenient location, observations made by observers worldwide, and also helps to provide the scientific community with a respectable set of visual data from both amateur and professional astronomers. [This is to complement the astrometric observations of comets published in the Minor Planet Circulars/Minor Planets and Comets and the CBAT publications]. Researchers can receive e-mailed files of ICQ-formatted data on a comet-by-comet basis via request to the Editor (icqcsc(at)
  2. General review of recent studies and observations made of comets, including news of discoveries/recoveries.
  3. Review and research articles by cometary astronomers on various aspects of cometary research. Potential contributors of articles for publication should see our guidelines for authors.
  4. Other observations of comets, including descriptive information and images/drawings of comets.
  5. Other useful information for the comet observer or researcher, including lists, recommendations, book reviews, etc. An ICQ Guide to Observing Comets was published in early 1997 as an aid to both beginning and experienced (amateur and professional) observers of comets.
  6. The ICQ includes reproduction of CCD images, photographs, and drawings of comets.
  7. General ephemerides for all observable comets (and some fainter interesting comets, such as 1P/Halley and those slated for future visits by spacecraft) are published in the annual Comet Handbook. This Handbook contains perhaps the best brightness predictions of any comet ephemerides available anywhere, as magnitude parameters are revised each year by utilizing all available comet data obtained over the previous year.
  8. The ICQ has organized numerous Workshops on Cometary Astronomy (WCAs) in the past two decades (including four in the U.S., three in Europe, and one each in Asia and South America). These WCAs have been designed to bring together amateur and professional astronomers to discuss the on-going observation of comets in a constructive co-working manner. The workshop highlights are usually summarized in the ICQ, sometimes with a special issue of the journal devoted to Workshop proceedings (papers).

The ICQ encourages authors to submit articles for publication in the journal; there is a referee system, as with most scientific journals. Actual computer images of comets (either obtained via CCD, or scanned into electronic images from drawings or photographs) may be sent to the ICQ for possible publication, but contact the Editor before sending images (e-mail address below), and read our instructions on sending images. Photometric observations should be contributed as noted below.

  • How to subscribe
  • ICQ Staff members
  • We are gradually making various articles and data of past published issues of the ICQ available here on the ICQ website.
  • The July 2009 quarterly issue of the ICQ is in preparation. The 38-page April 2009 quarterly issue of the ICQ was mailed on 2009 Oct. 14 and 15 to paying subscribers, along with the 124-page 2009/2010 Comet Handbook. The 42-page January 2009 quarterly issue of the ICQ was mailed on 2009 Apr. 7 to paying subscribers. The delayed 120-page 2008 Comet Handbook was mailed on 2009 Feb. 2 and 3 under the title 2008/2009 Comet Handbook, containing ephemerides for 2008 (for historical purposes) and the first half of 2009 (through July). [Other recent ICQ mailing dates.]

The ICQ Archive of Photometric Data on Comets. The ICQ maintains a computer database of photometric observations of comets, which includes all observations published in the printed ICQ plus data extracted from other journals (mostly historical, dating back to the 19th century). Each observation is given on an 80-character (80-byte) ASCII computer record with comet designation (this was expanded in 2002 to 129 columns for CCD observations); Universal Time (UT) year, month and date (to 0.01 day); magnitude (usually total visual), magnitude method, reference/source for comparison stars, and notes such as application of correction for atmospheric extinction, etc.; instrument type, aperture, and f/-ratio (and magnification, if visual) used for the observation; coma diameter in arcmin, and the coma's degree of condensation (DC); the tail length and position angle (in degrees); the reference indicating where the observation was published; and a 3-letter, 2-digit code for the observer.

Contributors of observations via e-mail should read this instruction sheet for the proper format. Never, ever use keyboard "TABs" when sending data of any sort to another person, because such characters will mess up regular ASCII files! The special codes used in this tabulation for such things as type of instrument, magnitude method, comparison-star reference, and notes are available here in the Keys to Abbreviations used in the ICQ archival tabulation. Information not easily put into tables are published in textual form in each issue of the ICQ as supplemental descriptive data; such information should be contributed separately from the tabulated data, listed by comet and then chronologically by UT date/time.

When a comet is less than 20 or 30 degrees from the observer's true horizon, and he or she is making a total visual magnitude estimate of the comet (which is done via comparison with a de-focussed nearby star whose known magnitude is taken from an appropriate catalogue), the observer needs to appropriately correct his observed value for atmospheric extinction. A standard procedure recommended by the ICQ and published in the July 1992 issue of the ICQ is now available here online.

Having troubles seeing comets because of all the artificial lights? Check out our page on light pollution!

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