Descriptive Information on Recent Comets
Provided below (by popular demand!) are selected recent reports of descriptive information on comets, to supplement the brightness data. Observers should be succinct, giving descriptive information after the listing of magnitude information, in the following form (a hypothetical example):
COMET C/1995 O1 (HALE-BOPP)
Descriptive information:
Feb. 17.42 UT: with a 32-cm f/5 L (157x), the comet showed bright
jets at p.a. 250 and 305 deg, with a fan of bright material spanning between
these two jets [D. W. E. Green, Cambridge, MA].
Thus, we will generally use the standard ICQ abbreviations for descriptive information that appear in the printed journal; so, for instrument type, we have L = reflector, B = binoculars, R = refractor, etc.. Note that select information submitted for publication in the ICQ will be extracted for posting here, so there is no need to submit twice. All observers, however, are encouraged to send their photometric observations in full ICQ-tabulation format at the same time that they submit observations for possible posting on this Web site or possible publication on IAU Circulars. Having some history (however brief!) of submitting data in proper ICQ tabulted format is a general prerequisite for having data posted on these Web pages. All times are UT.
Descriptive information, now in chronological order:
COMET C/1998 J1 (SOHO)
May 8.12: "Late this morning, I got out my 15-cm telescope, . . . occulted
the Sun first (using a small surfboard placed on top of the pergola), [and]
after checking out Venus, Jupiter and Saturn (all well to the west of the
Sun), I began the harder job of finding Comet C/1998 J1; I scanned a rectangle
of sky about 4 degrees high (N to S) and 8 degrees wide (E to W), centred
about 10 degrees northeast of the Sun (i.e., a box to the 'lower right' of
the Sun); I saw quite a lot; passing scraps of cloud, birds, airborne seeds,
and a couple of aircraft; but I also saw a triangular blob about 1' in
size, barely brighter than the sky, approximately 8-9 degrees north-northeast
of the Sun; this was found at 12:30 local time (1998 May 8 03:00 UT), and I
kept it in sight until another cloud blanket came over about 15 min later; my
telescope is a no-frills Dobsonian, so without a starfield I can't determine
an exact position or rate of motion for this object; however, it took about 2
min to drift through a 52x eyepiece field from E to W -- just like the planets
seen earlier, but quite unlike the clouds which were going (much faster) SW to
NE; was it a very high cloud? a stratospheric balloon? or was I successful?"
[Fraser Farrell, Christies Beach, S. Australia].
May 9: "Today I did not see anything at (or near) the expected position of
Comet C/1998 J1; Justin Tilbrook also tried at lunchtime today (with his 20-cm
telescope at Penwortham), and 'saw nothing except lots of thistle seeds' (he
used digital setting circles to locate the comet's expected position); to me,
the sky seemed 'whiter' today, suggesting a loss of transparency since
yesterday; to get some idea of today's limiting magnitude, I also looked for
a few planets and stars; Venus, Saturn, and Jupiter were all visible, and
Mercury was difficult; alpha Tau (Aldebaran) was just visible (mag about 0.9),
but gamma Ori was not (mag 1.7)." [Fraser Farrell, Christies Beach, S.
Australia].
May 9.1: "while the conditions were far from ideal, they were decent enough to
allow me to make what I feel is at least a half-way valid search for this
object; I didn't see anything, despite intensive searches with both 20-cm L
and 10x70 B; based upon my observations of Comet C/1975 V1 (West) under
similar geometry in 1976, and some stars I could see within the minutes after
the comet would've set (notably Rigel) I don't think Comet C/1998 J1 is any
brighter than m1 about 0" [A. Hale, Cloudcroft, NM].
May 9.52 and 10.40: w/ a 0.31-m Schmidt-Cassegrain telescope, "we attempted to
see the comet during daytime without-out success; sky conditions were good at
the site, 1.5 km high in the Italian Alps; as 'comparison star', we used
Mercury, which -- although further than the comet form sun -- was easily
visible at 75x (Jupiter and Venus also very easy); no defocusing of the
'comparison star' -- in-focus estimate; Zanotta also attempted to find the
comet w/ 20x80 B, using a roof top as sun shield, but nothing was seen" [R.
Parisio and M. V. Zanotta, Dalai-Lama Observatory, Promiod, Italy].
May 9.81: "not visible in bright twilight; searched for the comet within the
period when the sun was 4 to 7 deg below and the comet 5.5 to 2.5 deg above
horizon; at the end of the search Bellatrix was clearly visible" [KAM01].
May 10.1: "Our conditions were good here tonight, and I was able to make a
decent search, [but] still no comet; I tried with both 11-cm L and 10x70 B;
based upon the visibility of stars I could see (notably Rigel, Aldebaran,
and Bellatrix), I'm quite certain that the comet isn't any brighter than
m1 about 1, and I'm actually reasonably confident it isn't any brighter than
m1 about 2" [A. Hale, Cloudcroft, NM].
May 11.11: "Good conditions tonight -- still no comet; I searched with 10x70
B, 11-cm L, and 20-cm L, and I'm quite sure I would've picked up any comet
down to m1 about 2" [A. Hale, Cloudcroft, NM].
May 11.23: "Comet C/1998 J1 was easily seen from 5:28 (Sun alt. -6) to 5:43
UT (Sun alt. -9, comet setting in clouds, 1.5 degrees above the horizon) in
a 25.6-cm L F/D 5, 84x and 42x; well condensed (DC = 8/9), small (0'.5), with
a faint, short, fan-shaped tail about 5' long in p.a. 70 deg; unfortunately,
no stars close to the comet were seen, making its magnitude estimate difficult
(uncertain by more than 0.5 mag), though it must have been bright enough
(brighter than Aldebaran) to be seen quite easily at such low altitude (5 to
1.5 deg); observation made from Kahe Point Beach Park under clear skies
[Nicolas Biver, Kahe Point, Oahu, HI].
May 11.23: "The initial observation of this comet was made on May 11
(05h28m UT) by N. Biver (see above), using a 256-mm f/4.95 reflector, and the
comet was subsequently sighted by the undersigned using 20x80 binoculars; O.
Guyon and the undersigned both confirmed Biver's sighting of the comet in
the 256-mm reflector; the mag estimate given above was made when the altitude
of the comet was 4 degrees and the altitude of the sun was -7 degrees; the
mag estimate is based on a comparison with alpha Tau, observed on a significantly
darker sky background and is uncertain by about 0.5 mag; the comet was clearly
visible in the binoculars over a period of about 10 min, during which low
clouds occasionally interfered with the observation; the coma was highly
condensed (DC = 7-8), and no tail was visible in the binoculars [Haakon Dahle,
Kahe Pt., Oahu, HI].
May 12.1: "I was inspired by Biver's report [see above] (and the fact we may be
getting some bad weather in here soon) to try again last night; the sky was
completely clear of clouds, although the haze close to the horizon may have
been a bit worse than before due to blowing dust in the desert; still no
comet, despite searches with 10x70 B, 11-cm L, and 20-cm L; in the 20-cm L,
I could see the quartet of 65, 67, 69, and 72 Tauri (5 degrees east of the
comet) without any real difficulty (72 Tau is mag 5.5); allowing for the fact
that these stars were higher than the comet, I don't see how I could have
failed to see any comet that was brighter than m1 about 2.5; if our weather
holds, I'll see if I can try again tonight; the comet should be fairly close
to those stars" [A. Hale, Cloudcroft, NM].
May 12.79: w/ 20x80 binoculars, "very good sky conditions at the site, 1.3 km
high in the Italian Alps; Aldebaran (alpha Tau) easily seen; in-focus
negative mag estimate" [M. V. Zanotta, Monte Bisbino, Italy].
May 13.11: "tonight I was able to use the quartet of stars in Taurus (65,
67, 69 and 72 Tau) to get the 20-cm L right to the very vicinity of the
comet (as opposed to sweeping the general area); I still couldn't see
anything; based upon defocused images (about 2') of 65 and 69 Tau (magnitudes
4.2 and 4.3, respectively), I'm not quite sure I would have seen a comet of
that brightness at the lower elevation, but I feel reasonably confident about
a limiting brightness of m1 about 3.5" [A. Hale, Cloudcroft, NM].
May 14.03: "fairly good sky -- nothing there [w/ 20x80 B]; Aldebaran,
situated just a couple of degrees from the comet's position and at the
same altitude, was big and bright in the binoculars, so my 'fainter-than'
estimate is probably rather conservative" [J. Bortle, Stormville, NY].
May 14.354: "saw comet about 20 min after local sunset; he was using his
11x80 binoculars from the Port Noarlunga clifftop, so he had a sea horizon;
fortunately, he also had a small patch of clear sky in the right direction!;
he reports a tail approx 15' long directed eastwards; total magnitude 'fainter
than Aldebaran' and guesstimated to be mag 2 to 3; no other stars available
for comparison, and the comet itself was very low" [Peter Nation, via Fraser
Farrell, Christies Beach, S. Australia].
May 14.80: (comet not seen); "Aldebaran was bright and was seen via naked eye
for about 10 min before setting; w/ 16x50 B, no other star was observed
nearby; very good atmospheric conditions" [Victor R. Ruiz, Canary Islands].
May 15.13: "I had another attempt at a daylight observation today without
success; faintest star visible in my 15-cm telescope was beta Tau (V =
1.7), seen through thin cirrus]" [Fraser Farrell, Christies Beach, S.
Australia].
May 16.24: "comet clearly seen from 5:45 to 5:58 UT (setting in clouds, 1.9
degrees above the horizon) w/ a 25.6-cm f/5 L (42x, 84x); still rather
condensed (DC = 7/8), small (1'), with a faint short fan-shaped tail about
5' long in p.a. 110 deg; closest stars seen were 9 Ori and 4 ori and another
6.3-mag star" [N. Biver, Makaha, Oahu, HI].
May 16.34: w/ 7x50 binoculars, mag about 2.5-3: tail > 0.5 deg long
in p.a. 90-130 deg [C. E. Drescher, Warrill View, Queensland, Australia].
May 16.36-16.37: "comet at low altitude over sea horizon, with some thin cirrus
and twilight interfering; comparison stars beta Tau (1.7) and zeta Tau (3.0)
for m1 estimate; comet was visible naked-eye (once you knew where to look) but
the tail required binoculars; w/ 15-cm telescope, (pseudo)nucleus is a
distinctly brighter disc approx. 5" diameter within the coma, and appears pure
white even at this low altitude; coma colour is a dull white (similar to
Mercury naked-eye); main tail is faint grey, thin (< 15' wide) and straight
(ion tail?); coma merges into a broad fan-like secondary tail, which extends
about 20' from nucleus between p.a. 50 and 150 deg (this was bounded by
slightly brighter edges or 'rays' extending to about 25' from nucleus); no
other tail structure seen" [Fraser Farrell, Christies Beach, S. Australia].
May 17.241: "comet observed from 5:45 to 6:04 UT w/ a 25.6-cm f/5 L (42x,
169x); comet condensed (DC = 7), small (1'.5), w/ a faint, short tail
0.2 deg long in p.a. 100 deg; it was observed close to 6 Ori (12' away
at 5:47.3 UT) and nearly aligned with 7 Ori, which enabled a much better
estimate of its position:
1998 UT R.A. (2000) Decl.
May 17.241 4 54.6 +11 15
(this position is uncertain by 2' at most, and seems still displaced relative
to IAUC 6906 -- 0.5 deg NW)" [N. Biver, Oahu, HI].
May 18.38: "easily visible to the naked eye; in binoculars, the first 2
degrees of tail is bright (dust?) and faintly extends to 5 degrees (gas?)
in length" [M. Mattiazzo, Adelaide, South Australia].
May 18.69-18.70: "comet bright and easy in 10x50 binoculars w/ very bright,
condensed central condensation and thin spike-like tail, traced to 45' in
p.a. 112 deg under poor, hazy conditions; nevertheless, the comet was just
visible to naked eye" [T. Cooper, Bredell, Kempton Park, South Africa].
ICQ
