(for comets 1 through 600)
as of July 6, 2017
|When I inaugurated "Countdown to 500 Comets" I included a statistics page that included various statistics and other comments about the first 400 comets I have observed. Similarly, when I instituted "Counting Comets" after reaching comet number 500, I included a similar statistics page that analyzed and discussed the first 500 comets (as well as a separate analysis and discussion of comets 401 through 500). With "Continuing With Comets" it only seems appropriate that I include a statistical analysis of the first 600 comets, especially since, with the exception of the two comets listed below, I am now completely finished with the first 600. Although I am picking up "Continuing With Comets" in mid-stream with comet no. 622, I have decided to exclude all the comets after no. 600, in significant part because several of them are still ongoing at this time. Perhaps I will complete another analysis once I reach comet number 700 that will include these comets.
The two comets of the first 600 comets that can be considered "ongoing" at this time are:
174P/Echeclus P/2000 EC98 (no. 384): As I indicated on the original statistics page, this Centaur comet underwent a dramatic outburst in late 2005 when located over 13 AU from the sun, and I was able to obtain a handful of observations of it as an extremely faint object in early 2006 before the outburst subsided. It underwent another outburst in May 2011 that I was not successful in observing, but after passing perihelion in April 2015 (at a still distant 5.8 AU from the sun) it underwent yet another outburst in August 2016, which I did successfully observe on two occasions -- for a total observational interval at this time of slightly over 10 1/2 years. The comet does not pass through aphelion until November 2032, and it is at least theoretically possible that it could undergo additional outbursts between now and then.
29P/Schwassmann-Wachmann 1 (no. 498): I picked this comet up shortly after it went through aphelion in late 2011. It does not pass perihelion until March 2019, and it is at aphelion again in September 2026. The comet is notable for its outbursts, which occur unpredictably and randomly, and it will almost certainly continue to undergo occasional outbursts for as long as I continue to follow it.
Some general comments
The 600 comets comprise a grand total of 6776 separate visual observations, from 1970 February 2 to 2017 June 30 (most recently).
The 600 comets comprise 436 separate comets, for a total of 164 "repeat" comets. I have observed 76 separate comets on two or more returns; collectively, these constitute 240 out of the 600 comets (40.0%). I have observed one comet (2P/Encke) on 11 returns, one comet (81P/Wild 2) on 7 returns, 1 comet (19P/Borrelly) on 6 returns, 11 comets on 5 returns, 10 comets on 4 returns, 17 comets on 3 returns, and 35 comets on 2 returns.
Of the 352 periodic comets that have been numbered as of this writing, I have observed 136 (within the first 600 comets -- I have observed one more since then), or 38.6%. I have observed 75 of these (21.3%) on two or more returns, and 61 of these (17.3%) on one return only. I have observed 40 (11.4%) of the numbered periodic comets on their discovery return, and of these have observed 18 on at least one subsequent return; I have observed 7 (2.0%) of the numbered periodic comets on their "rediscovery" return and have observed 1 of these on at least one subsequent return. I have observed 10 as-yet-unnumbered Jupiter-family comets on their discovery returns (one of which has just recently been recovered and will likely be numbered soon), and 14 as-yet-unnumbered Halley-type comets on their discovery returns.
The average perihelion distance of the first 600 comets is 1.533 +/- 1.036 AU, and the median is 1.377 AU. They have ranged from 0.006 AU for Comet Lovejoy C/2011 W3 (no. 500) to 8.454 AU for Comet 95P/Chiron P/1977 UB (no. 196). 24 of these comets (4.0%) have a perihelion distance of 0.20 AU or less, and 15 (2.5%) have a perihelion distance of 5.0 AU or larger.
The average tracking interval is 140.82 +/- 337.15 days, and the median interval is 68.75 days. 29 comets (4.8%) have an observational interval of 0, i.e., only a single observation. The longest tracking interval was for the 2004 return of Comet 29P/Schwassmann-Wachmann 1 (no. 226), which lasted for 14 years, 4 1/2 months (specifically, 5252 days). I followed 47 (7.8%) of these comets for over one year, 23 of these (3.8%) for over 18 months, 10 of these (1.7%) for over two years, 7 of these (1.2%) for over three years, and 4 of these (0.7%) for over four years.
I have picked up my average comet 69.56 +/- 257.01 days before perihelion passage, and my median comet 37 days before perihelion. For 164 comets (27.3%), I did not obtain my first observation until after perihelion. Of these, 57 (34.8%, 9.5% of the total) were not discovered until after perihelion. My first observation of 17 comets (2.8%) came more than one year before perihelion, and my first observation of 2 comets (0.3%) did not come until more than one year after perihelion. My earliest pre-perihelion first observation was for comet 174P/Echeclus P/2000 EC98 (no. 384), which came 3389 days (9 years, 3 months) before perihelion, and my latest post-perihelion first observation was for the 1974 return of Comet 29P/Schwassmann-Wachmann 1 (no. 47), which came 2637 days (7 years, 2 1/2 months) after perihelion. (I did not begin looking for this comet until almost seven years after perihelion.)
I have followed my average comet until 71.16 +/- 210.55 days after perihelion passage, and my median comet until 45 days after perihelion. My final observation for 122 comets (20.3%) came before perihelion. My "final" observation for 1 comet (0.2%) came more than one year before perihelion; this is the 2019 return of Comet 29P/Schwassmann-Wachmann 1 (no. 498) and thus will likely eventually no longer be true. My final observation for 12 comets (2.0%) came more than one year after perihelion. My earliest "final" observation with respect to perihelion is, as just mentioned, for the 2019 return of Comet P/Schwassmann-Wachmann 1 (no. 498), presently 615 days (1 year, 8 months); excluding this, my earliest final observation was 364 days before perihelion, for Comet P/Shoemaker-Levy 9 1993e (no. 378). My latest final observation is 2985 days (8 years, 3 months) after perihelion, for the 1974 return of Comet 29P/Schwassmann-Wachmann 1 (no. 47).
My average number of observations per comet (rounded to the nearest whole number) is 11 (mathematically, 11.3 +/- 14.6), and the median is 8. As previously mentioned, 29 comets (4.8%) have only a single observation, and 56 comets (9.3%) have only two observations. 11 comets (1.8%) have 50 or more observations, and 3 (0.5%) have 100 or more observations. The comet with the most observations is Comet Hale-Bopp C/1995 O1 (no. 199), with 182 observations. For periodic comets with observations from all returns combined, the comet with the most observations is 29P/Schwassmann-Wachmann 1, with 309 observations over four returns.
The average peak brightness I have observed for the comets is magnitude 10.6 +/- 3.1, and the median peak brightness is magnitude 11.3. The brightest comet I've observed is Comet McNaught C/2006 P1 (no. 395), for which I measured a peak brightness of magnitude -4 (in daytime). The faintest brightness I have ever measured for a comet is magnitude 15.4, for Comet 95P/Chiron P/1977 UB (no. 196) during my sole observation during its 1998 opposition. I have observed 59 comets (9.8%) which reached a peak brightness of magnitude 6.0 or brighter; of these, I have observed 42 comets (7.0%) with my unaided eye. I have observed 15 comets (2.5%) for which I observed a peak brightness of magnitude 14.5 or fainter; of these, 4 comets (0.7% of the total) achieved a peak brightness of magnitude 15.0 or fainter.
For the purpose of the below calculations, I consider "date 0" to be the date that I acquired my first telescope, i.e., January 17, 1970. The average interval between additions to my tally (rounded to the nearest day) is 28 days (mathematically, 28.3 +/- 39.1 days), and the median interval is 17.5 days. There have been two occasions when I have added three comets to my tally in one night (numbers 181 through 183 on December 14, 1993, and 491 through 493 on August 7, 2011), and an additional 29 occasions when I have added two comets to my tally during a single night. My longest interval between tally additions is 366 days, prior to Comet Bradfield 1972f (no. 7). I have added 267 comets (44.5%) during the evening hours, i.e., before local midnight, and I have added 333 comets (55.5%) during the morning hours, i.e., after local midnight. Of the 29 occasions when I added two comets during a single night, four of these involved one comet during the evening hours and one comet during the morning hours.
Other miscellaneous comments
24 of the comets (4.0%) have approached to within 0.2 AU of Earth during their respective apparitions, and of these, 7 comets (1.2%) have approached to within 0.1 AU of Earth.
The smallest heliocentric distance at which I've observed a comet is 0.171 AU, for Comet McNaught C/2006 P1 (no. 395), which I was observing (in daylight!) at the moment of perihelion. The largest heliocentric distance at which I've observed a comet is 13.049 AU, for Comet 174P/Echeclus P/2000 EC98 (no. 384) during its outburst in early 2006. The smallest geocentric distance at which I've observed a comet is 0.024 AU, for Comet PANSTARRS P/2016 BA14 (no. 595) during its flyby of Earth in March 2016, and the largest geocentric distance at which I've observed a comet is 13.022 AU, again for Comet 174P/Echeclus (no. 384).
The longest tail I have ever observed on a comet is 70 degrees, for Comet Hyakutake C/1996 B2 (no. 212), shortly after its close approach to Earth in March 1996.
My record for most comets observed in one night is 15, which took place on the night of March 21-22, 2009. My record for most comets observed in one year is 38, set in 2015. My record for most comet observations in one year is 334, set in 2008.
There were two occasions when I observed two comets simultaneously within the same telescope field, three occasions when I observed two comets simultaneously within the same binocular field, and two occasions when I observed two comets simultaneously with my unaided eye.
The most productive month for comet discoveries (and recoveries) for my first 600 comets is May, with 57; the least productive is February, with 22. The most productive month for comets passing through perihelion is December, with 75; the least productive is June, with 26. The most productive month for adding the first 600 comets to my tally is August, with 68; the least productive is June, with 30.
A total of 235 different names are represented in the tally of the first 600 comets; of these, 208 (88.5%) are of actual people, 18 (7.7%) are observatories or survey programs; 5 (2.1%) are spacecraft or space-based telescopes; and 4 (1.7%) are mythological or fictional characters. 108 (46.0%) of the names (including Hale) appear only once. The name that appears most often in the tally is LINEAR, with 68 appearances, followed by McNaught (27), Shoemaker (20), Machholz (18), Levy (17), and Hartley (15). The top name on this list, LINEAR (68 entries of 66 separate comets), alone accounts for 11.3% of the entire tally.
The observing locations for my first 600 comets include 10 states within the U.S. (Arizona, California, Colorado, Maryland, New Mexico, Oklahoma, Tennessee, Texas, Utah, and Washington) plus the District of Columbia, and from six countries outside the U.S. (Australia, Indonesia, Iran, Mexico, New Zealand, and Zimbabwe) as well as from international waters in the Pacific Ocean (during my Navy years) and the Caribbean Sea (during an eclipse cruise).
As of this time I had made unsuccessful visual attempts for 251 other comets (a handful of which are very recent, and which I may successfully observe in the future). Of these comets, I successfully imaged 13 of them with CCD when I had my imaging program operational.
As I discuss in the "special note" on the "Continuing With Comets" main page, I have observed several "asteroids" which could potentially be "extinct" or "dormant" comets and which could, at least theoretically, be added to my comet tally retroactively if future observations justify including them as "dual-status" objects. While the make-up of a list of such objects is perhaps somewhat subjective, as of this time I have observed 20 "asteroids" (on a combined total of 23 "returns") that I consider as viable candidates worthy of serious consideration. There are a handful of additional such objects for which I have made unsuccessful visual attempts over the years; I successfully imaged one of these with CCD when my imaging program was operational.
From an entirely subjective standpoint, the "best" comet I have observed is Comet West 1975n (no. 20) during its appearance in the morning sky in early March 1976.
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