The Great Christmas Comet of 2011, 2011 W3 (Lovejoy) Options

[Guest_Sunspot_*]

http://sungrazer.nrl.navy.mil/index.php?p=.../birthday_comet

Possible very bright sungrazing comet coming mid December - Comet Lovejoy C/2011 W3 (Lovejoy)

Information in the link above.

[Guest_Sunspot_*]

Here it comes

http://sohowww.nascom.nasa.gov//data/REPRO...0830_c3_512.jpg

[titanicrivers]

And check out the SOHO Movie Theater! Choose LASCO C3 and the latest 20 or so images.
http://sohodata.nascom.nasa.gov/cgi-bin/soho_movie_theater

[Mongo]

Spaceweather

COMET LOVEJOY UPDATE: Matthew Knight of the Lowell Observatory and JHU-APL reports: "As of 16:30 UT on Dec. 15th, Comet Lovejoy has reached magnitude -3, possibly brighter. It is starting to saturate SOHO images even with narrow filters and shorter than normal exposure times." The comet is now brighter than Jupiter, but not quite as bright as Venus. If these developments continue apace, Comet Lovejoy could become visible to the naked eye in broad daylight before the end of Dec. 15th.

[stevesliva]

If these developments continue apace, Comet Lovejoy could become visible to the naked eye in broad daylight before the end of Dec. 15th.

NFW. I'll have to squint through some clouds.

[Mongo]

Same here. Right now it's overcast from horizon to horizon where I am.

[Juramike]

It lives!

http://www.youtube.com/watch?feature=playe...p;v=LBJ2mkI1rSc

[Mongo]

Here is another video:

http://sdoisgo.blogspot.com/2011/12/phoeni...et-emerges.html

I should add that the comet may look faint in these videos, but the cameras are optimized to stare at the surface of the sun. The fact that the comet is visible at all indicates its tremendous brightness.

[Explorer1]

That's one tough cookie....
Any estimate for how close it got (in terms of solar radii)?

[jamescanvin]

140,000 km (1.2 solar radii) above the surface

[Guest_Sunspot_*]

Seems to have left it's tail behind.

http://lasco-www.nrl.navy.mil/javagif/gifs...216_0930_c3.gif

[Mongo]

140,000 km (1.2 solar radii) above the surface

Actually, the radius of the Sun is 695,500 km, so Comet Lovejoy approached to 0.2 solar radii above the photosphere.

[Toma B]

Seems to have left it's tail behind.

That tail was so OUT it's growing itself new HOT tail.

http://lasco-www.nrl.navy.mil/javagif/gifs...216_1530_c3.gif

[Mongo]

It is still very soon, but it appears that Comet Lovejoy is actually brighter than it was at the same distance from the Sun on the way in, and continues to brighten. (This is not a total surprise -- historically, close sun-grazers have tended to be more spectacular after perihelion than before, provided they survive it.) It could end up being a brilliant comet in the southern hemisphere in the coming days, once it moves a bit further from the Sun's glare.

Quicktime movie

(The nucleus's brightness can be very crudely estimated from the size of the white oversaturation bars extending from the nucleus. They are already longer than any seen by this camera on the inbound trajectory.)

[Guest_Sunspot_*]

The Ion tail has reappeared too.

[Mongo]

Another movie:

SOHO LASCO C3

This site only shows the last 3 days of observation, so it's fine for the next day or so, but after that it will be less useful. But right now, it's spectacular!

[nprev]

The next few days may prove interesting...and spectacular for those south of the Equator.

[SteveM]

And check out the SOHO Movie Theater! Choose LASCO C3 and the latest 20 or so images.
http://sohodata.nascom.nasa.gov/cgi-bin/soho_movie_theater

You can trace the entire mind-blowing sequence from entrance to exit by selecting 2011-12-15 as the start date and 2011-12-17 as the end date.

[Guest_Sunspot_*]

Visual sightings starting to come in now.

[Floyd]

Why is the view better from south of the Equater? Unless you are above the artic circle...if you can see the sun, you can see the comet?

[Mongo]

Comet Lovejoy is no longer a daylight comet, so darkish skies are needed to see it with the unaided eye.

Basically, the orbit of this comet appears from Earth at about a 45 degree angle from the ecliptic towards the south. This means that at mid-southern latitudes, the orbit takes the comet almost directly 'above' the sun at sunrise, so that it will be visible (in the coming weeks) well before sunrise, in fairly dark skies. Therefore the contrast of the comet against the sky will be very good, and its tail will be quite visible (and indications are that the tail will become quite lengthy in the coming weeks).

On the other hand, at mid-northern latitudes the comet will be moving away from the sun in a direction almost parallel with the horizon at sunrise, so it will not even appear above the horizon until the sun is nearly rising (and turning the sky very bright), and remain lost in the near-horizon haze until full daylight. The contrast of the comet against the sky will be far worse than from the mid-southern latitudes, and it is likely that it will not even be visible to the naked eye at all, unlike the situation from the mid-southern latitudes where it is expected to be quite prominent in the pre-sunrise sky.

So we have had two Great Comets in a row (McNaught and now with any luck Lovejoy) best seen from the mid-southern latitudes, and poorly visible from the mid-northern hemisphere. Oh well, those are the breaks.

[Floyd]

Thanks Mongo, great explanation!

[MaG]

Our friends took image from Argentina today morning.


http://www.kommet.cz/

And here's my imagination of comet's path in LASCO C3..



What an exciting weekend.

[Mongo]

This was posted today by highly respected astronomer John Bortle on the comets-ml mailing list:

Based on the brightness estimates from early this morning, reported here on comets-ml, it would tentatively seem that comet 2011 W3 is currently only slightly fainter than was Comet Ikeya-Seki at about the same interval post-T and holding its newfound intrinsic brightness. If this is anywhere near correct and that the tail development evident from spacecraft images is at least fairly representative of what might be seen visually, then observers should begin seriously searching for the comet's bright tail projecting up out of the morning twilight beginning at dawn tomorrow.

The tails of some of the major sungrazing comets have been extraordinarily bright. So much so, in fact, that even their exact terminus, usually a vague and extremely ill-defined feature for more typical bright comets, can be clearly evident to the unaided eye. In the case of the Great March Comet of 1843, the Great September Comet of 1882 and 1965's Comet Ikeya-Seki, the tails appeared rather like segments of a bright searchlight beam, so high in their surface brightness that their total length was distinctly obvious to most observers.

Comet Lovejoy's apparition has been so bizarre up to this point that it is truly difficult to anticipate just what might happen next. Even more hazardous would be to attempt to accurately predict the exact sort of tail it will unfurl in the morning sky. However...in my opinion the potential is there for something quite unusual, perhaps even extraordinary, to present itself, particularly by virtue of the current geometry between the comet and Earth, as it presents the most favorable circumstances possible for observing the tail of a Kreutz sungrazing group comet.

I personally await with great anticipation the first reports of Comet Lovejoy's tail as the comet exits the twilight and begins to traverse the morning skies of the Southern Hemisphere. Please...be complete, accurate and as detailed as possible in describing what you see, the coming event may prove historic.

J.Bortle

[nprev]

...if John Bortle says anything about comets, I believe it.

Those are some strong words. Wow.

[Stu]

Wow.

Ok, now I really am officially northern hemisphere hacked off. First McNaught dazzles southern hemisphere observers only, now Lovejoy...

[nprev]

Now, now, Stu...we had Hale-Bopp!

But, yeah, I feel some hemispherical comet-envy myself here. If I had the money & time my butt would be on the next flight to the most southerly location with good weather predicitions possible.

[scalbers]

Wow.

Ok, now I really am officially northern hemisphere hacked off. First McNaught dazzles southern hemisphere observers only, now Lovejoy...

Just for the record, there were things of interest to observe with McNaught from 40N latitude. Just around perihelion time, it actually was to the NE of the sun and best visible from northern latitudes at mag -5 to -6. I saw it in broad daylight in binoculars, and naked eye just after sunset. Furthermore, the ghostly outer rays of the tail were pointing straight up from the western horizon after evening twilight ended a few days later.

Now with Lovejoy, it was spotted in broad daylight from France - of course a mid-northern latitude - image can be seen at this link:

http://spaceweather.com/submissions/large_..._1324194382.jpg

Really would be interesting to plot this comet's magnitude vs solar elongation in comparison to McNaught and Ikeya-Seki.

Steve

[Mongo]

Report of a daylight sighting of Comet Lovejoy on comets-ml mailing list:

Daylight Comet!

by Rick Baldridge



The amazing happened. Comet Lovejoy (C/2011 W3) survived what was thought to be a suicide plunge into the solar corona, passing only 78,800 miles from the surface of the Sun on December 16th – not quite 1/10th a solar diameter! Surprisingly, the comet reappeared on SOHO LASCO images barely 1 hour after perihelion passage, prompting Brian Day of NASA/Ames and I to attempt a daylight observation.

We ran up to Foothill College Observatory (Los Altos Hills, CA) at lunch time on Dec 16th and opened up the dome. I quickly made a 3" aperture off-axis mask for the Meade 16" Schmidt scope, which allowed me to use the dome shutter as a glare shield, keeping direct sunlight out of the telescope tube assembly. Comet Lovejoy was barely 4° west of the sun during the attempted observation.

Finding Venus first to focus on, I used coordinates from JPL HORIZONS to center the `scope on the comet's expected position. After looking through a 127x eyepiece for a few moments – THERE IT WAS! A very star-like nucleus with a faint but obvious fan shaped glow streaming away from it. The fan was maybe 20 arc-seconds long. A very rough guess was the nucleus was magnitude -1, based on my impression of the appearance of Mercury years ago at a similar solar elongation. This initial sighting came at 11:48am PST (Dec 16th at 19:48UT)

Brian Day was quickly called, who had just driven into the Observatory parking lot. He came up, took one look in the eyepiece, and after adapting to the brightness of the background sky, exclaimed, "DAMN! There it is!"

We were ecstatic! Seeing a daylight comet is an extremely rare thing, and so close to the sun – only 4 degrees. Truly amazing!

Unfortunately, Brian and I did not have our DSLRs to attempt taking a photo. We tried our cell phone cameras, holding the lens up to the eyepiece using afocal projection, but to no avail.

It was an experience we will never forget!

[nprev]

Wow.

Mongo, please keep feeding salient info like this at your discretion. I think that there is a SLIGHT chance that this thing might be visible to unskilled observers over the next few days, and anything we can do to promulgate awareness would be very useful. Thanks!!!

[Mongo]

For those readers who are in the southern hemisphere, here is a finder chart for Comet Lovejoy from latitude 35 degrees south, for this Tuesday morning before sunrise:



This is from Where to look for Comet 2011 W3 (Lovejoy) Tuesday morning

[Mongo]

From Malargue, Argentina this morning:

[Mongo]

Finder chart for 35 degrees south on Wednesday morning:

[Stu]

Tail sighted - and photographed - from Australia...

http://www.spaceweather.com

[Mongo]

This is interesting. From the comet-ml mailing list:

On classical V-filtered pictures from 30-cm Meade SCT F/10 (0.66x) are more features visible today!

Some faint "outer tail" is now visible and there is something new, which looks like a ray in tail from nucleus looks like a synchrone.

[nprev]

Magnificent!!!

[machi]

Amazing images, it's unbelievable, that this little comet survived flyby so close to Sun!

[tasp]

Impressive it withstood the tidal effects too.

[Mongo]

Latest today from comet-ml mailing list:

Hi all,

I observed Lovejoy this morning from Woolbrook, NSW, i am so excited, at 4am AEDST i took an image of the Eastern horizon and upon looking at the image i noticed a thin "search beam" like extension pointing up from the SE, tilted a little to the North. I looked with my naked eye and saw what appeared to be headlights of a car near my horizon but it didn't seems to move, long story short....the tail i measured over the next 50 mins was nearly 15 degrees long and in moonlight!

Clouds not long intervened at dawn and i tried for the comet head but saw nothing in my 10" dob.

Images to follow!

Cheers,
Chris Wyatt
Walcha, NSW
Australia

The comet, as expected, is getting more prominent as it starts to move out of the morning twilight.

The thread title is "The SOHO Birthday Comet", but I think a better name would be "The Great Christmas Comet of 2011", since with the new moon on December 24th, viewing conditions should greatly improve just in time for Christmas. Not to mention that by then it should be well clear of the morning twilight, and significantly closer to Earth with a better viewing geometry.

[nprev]

In moonlight, no less.

Good grief.

[Mongo]

Finder charts for 35 degrees South latitude on Thursday morning:

[jamescanvin]

The thread title is "The SOHO Birthday Comet", but I think a better name would be "The Great Christmas Comet of 2011"

I agree, I added the "2011 W3 (Lovejoy)" subheading earlier today to help identify the thread and have now changed the main title to your suggestion.

[Mongo]

Oh-oh. That title change may have been premature. It appears that the comet nucleus may have broken up within the past few hours.

From comet-ml post #18949:

Comets gets weaker, today pictures in V-filtered exposures giving at 20.34 UT: ~3.5 mag (comparsion tar TYC 7364-2287-1 ).

Filtered images from FRAM this morning (average of best pictures).

http://www.kommet.cz/datas/users/1220average_r_dbe_1.png

http://www.kommet.cz/datas/users/1220average_v_dbe_1.png

From comet-ml post #18950 by Gary Kronk:

These are very interesting images. Either the nucleus and bright tail ray have been merged during the processing of these images or the distinct nucleus has broke up...appearing like a bar. This latter description has been given before when nuclei have been reported to break up.

From comet-ml post #18952:

This animation from Karl shows the comet fading in STEREO HI1A. A dust tail wedge is getting longer and broader, sits on top of original dust tail. There is a small recurring spike tail near and below the head that seems to be from a rotating nucleus.

http://sungrazer.nrl.navy.mil/index.php?p=...18\_19.gif

Where would all the new dust be coming from? There rate of new dust tail extension is occurring rapidly. Possible breakup starting?

From comet-ml post # 18955 by Gary Kronk:

The sudden appearance of bright rays are not uncommon when it comes to a comet breaking up. Check out the following link on my Cometography web site that discusses comet C/1999 S4 (LINEAR):

http://cometography.com/lcomets/1999s4.html

If you scroll down a bit, you will see two pictures from 1999 July 21, that show a bright tail ray. Within days the comet was unmistakably breaking up.

By the way the link to my comet Lovejoy web page is as follows:

http://cometography.com/lcomets/2011W3.html

Sincerely,
Gary

[Mongo]

A photo from this post:

After reading Ian Cooper's post I decided to drive south to the Mandurah Esturary around 2 am for a look. Light pollution is pretty low down there. I took 2 cameras, 1 for timelapsing and the other stills. I started taking images around 2:50 WST. At around 3:10 the first hint of tail appeared above the trees and by 3:15 I could see it visually. It stayed in clear view (non averted vision) from then until around 4:10 (deep twilight). An awesome sight. [...] If you're lucky enough to have clear skies tomorrow, I urge you to go out before the onset of astronomical twilight. If the comet is anything like it was this morning you won't be disappointed.

[Mongo]

From comet-ml post #18958:

Hi all,

When I first looked out this morning (from Cowra in central NSW) and saw the layers of high and middle-level cloud, I almost went back to bed. But after a few minutes deciding, I set up the 25x100 binocular telescope and started to sweep along the horizon which, surprisingly, was clear for the first two or three degrees. At 4.20 local summer time (1720 UT) I noticed something like a distant searchlight beam rising over the slope of a small hill which sports the rather grandiose name of "Porter's Mount". With the sky becoming bright, I could see a clear feature on the local horizon (a tree about two thirds of the way up the grassland slope of Porter's Mount) near where the beam emerged and, finding this without the telescope, I could then see about 2 - 3 degrees of tail rising up to a bank of heavy cloud. The tail must have been quite intense to be seen in such a bright sky and, from the calculated position of the head, at least 7 - 8 degrees long (although most of this was not seen. Neither was the head as the sky had become very bright by the time it would have cleared Porter's Mount).

On a slightly different topic, as one of the few Ikeya-Seki veterans in this group, it is probably timely to sound a warning not to give up on this comet because of the degree of fading that has obviously taken place. Back in 1965, the arrival of I-S at perihelion was surrounded by a lot of media hype. Predictions that a comet brighter than the Moon was coming, while they turned out to be technically true, failed to make clear that the comet would be only a few arcminutes from the Sun's limb at that time and would fade very rapidly afterwards. Of course, the general public missed much of the display at perihelion and dismissed the comet as a dud. On the day of perihelion, Fred Whipple called it "a scientist's comet"; one that was great for astronomers but a disappointment for the public. Unfortunately, the media dropped the subject (by and large) and when the "public" show occurred over a week later, only those who normally rose before dawn for work or other purposes saw it.

My first couple of views post perihelion were not all that exciting. High cloud always seemed to shroud the eastern horizon and by the time the comet cleared this, the sky was very bright and the comet looked washed out with only a small diffuse spot of a coma and a fading tail. Then, exactly 10 days after perihelion, there was a morning of exceptional clarity and by that time the comet was far enough from the Sun to be rising in a dark sky. The sight was magnificent. In the dark sky, the coma appeared brighter than the earlier twilight views and looked small and dense. As for the tail, this appeared (as John Bortle has written on several occasions to this group) "solid", not diaphanous like the tail of a normal comet. And there was little "normal" about Ikeya-Seki! Today, we would probably think of laser beams or Star-Wars light sabres ... but this was back in 1965!!

Now, I am certainly not saying that W3 will become as remotely spectacular as I-S, but the lessons of 1965 are worth noting. The comet may become faint, but the tail may well retain relatively high surface brightness for quite some time and be impressive in coming days as it pulls out from the twilight (and moonlight). Don't dismiss this comet just yet! There may still be surprises in store.

David

In response to this, John Bortle wrote in comet-ml post #18961:

David is absolutely correct. I anticipate that the spectacle is only likely to grow better with time as the tail moves out of the morning twilight. Keep in mind that the brightness of a sungrazer's dust tail seems to fade much more slowly than does that of the coma, following closer to a rate dictated by the inverse square law. Likewise, Comet Lovejoy's tail is more-or-less still approaching Earth as the comet retreats from the Sun, slowing the fading process even further.

Go back and consult some of my earlier posts concerning the development of Comet Ikeya-Seki's post-T dust tail. Such may well foreshadow the sort of evolutionary path that the tail of Comet Lovejoy may see in days to come on a somewhat more modest scale.

Folks, be assured that the show isn't over yet by any means.

J.Bortle

[Mongo]

From comet-ml post #18977:

Hi All,

I have to eat my words to friends about this comet. Looks just like Ikeya-Seki in 1965. A really beautiful Xmas present.

I got a series of images this morning but have no website, so one of the better ones appears in the nzastronomers site.

I estimated the visible tail length at 18 degrees, and the head was still out of sight below the local horizon here in New Plymouth, New Zealand.

[Mongo]

From this Brazilian Portuguese-language blog:

[Mongo]

From comet-ml post #18990 by Robert McNaught:

After several nights or mornings of poor weather, and the prospect of these continuing here at Siding Spring, I decided it was time to move. This morning gave an opportunity to find clear sky about 20km to the west, away from the mountain fog and orographic cloud. And boy, was it worth it! This is a most beautiful comet.

The tail was very obvious to the naked eye, rather brighter than the Milky Way in Circinus, Norma and Ara but not quite as bright as in Crux and Carina. The split between the dust and gas tails was clearly evident to the naked eye.

10x50 binoculars didn't show much more tail length, but structure was present, especially the "spine" along the southern edge of the dust tail, continuing past the bifurcation of the dust and gas tails. The end of the dust tail fades off very rapidly and naked eye, 10x50B and various photos have the tail reaching RA 15h54m Dec -40.0 (2000) The ephemeris position at that time was RA 17h02.3 Dec -34d56' (2000) giving a dust tail of 14.3 deg. The gas tail is perhaps 1 deg longer but fades away much more gradually and thus has a less well defined end point. The edges of the dust and gas tail are very sharply defined.

The tail brightness from the bifurcation towards the head was quite uniform, but as twilight progressed, the tail near the head became lost in the twilight and I didn't see the head visually or record it on photos. This is not a strong conclusion, as I had to move to a better location to find a lower horizon and the sky brightness probably beat me. I'd be reasonably confident that from tomorrow onwards I'll be able to make some meaningful statement about the visibility of the head.

To place this comet in the pantheon of modern comets (essentially subjective), I'd put it in the class of Hale-Bopp, Hyakutake and Bennett with this morning's view.

I'll try to get some photos up later today.

Cheers, Rob

[Mongo]

Here is a photo from this morning by outbackmanyep from Bendemeer, New South Wales, Australia:

[Mongo]

Photo from this site:

[ugordan]

Wow.

[scalbers]

Very nice. Looks rather brighter than pieces of Milky Way in the image. With the help of Mongo's finder chart one can see Antares in the lower left corner, and Mu Scorpii to the upper right of the comet head.

On the spaceweather.com site there is a timelapse of the comet rising as seen from western Australia by Colin Legg. Worth looking at full screen:

http://vimeo.com/34007626

[Mongo]

There are some incredible movies now available from the Sungrazer website, which is linked to in the very first post in this thread.

First is this 7MB Quicktime movie from STEREO/SECCHI COR-1B. Very spectacular -- you first see the comet approaching the sun from the lower right, then the headless tail receding to the upper left, then the tail-less comet nucleus moving away from the sun toward the lower right as it begins to generate a new tail.

Second is this 30MB WMV movie from STEREO/SECCHI HI-1A, also a very striking movie of the comet departing from the sun..

[Mongo]

The latest image of Comet Lovejoy, by Colin Legg. The comet is starting to move into darker skies.



Here is the latest report from Dave Herald from comet-ml post #19013:

At long last the skies are clear in the Canberra region. The nucleus for Lovejoy doesn't rise for another half hour. But already the tail is visible to the naked eye, extending a full 10 deg above the horizon. The surface brightness is similar to the Magellanic clouds - even though they are higher in the sky.

Dave Herald
Murrumbateman, Australia

[Stu]

Good grief... view from the ISS...

http://www.flickr.com/photos/nasa2explore/6555113049

[Tesheiner]

Wow!

[Stu]

Lovejoy Rising...

[centsworth_II]

This time lapse via a tip from Emily's Twitter:
http://www.nasa.gov/multimedia/videogaller...ia_id=125774121

[Stu]

Just saw that, wish I'd noticed there were earlier images to begin the sequence sooner. Oh well...

[Mongo]

From comet-ml post #19028 by Dave Herald:

A bit more on the brightness...

The comet’s tail for the first 12+ degrees is definitely considerably brighter in surface brightness than the adjacent Milky Way band at similar altitudes. My comparison with the Magellanic clouds was of the tail at around 10 deg altitude, with the Magellanic clouds at 40 to 50 deg altitudes, with significant atmospheric absorption at low altitudes.

Re tail length. With the nucleus at 17h 00.6m –37d 10’ (but no condensation visible at that location), the dust tail extended to around 15h 44m, –43.0d, and the ion tail extended to about 15h 58m, –44.3d – giving tail lengths of around 16 deg.

Rob refers to P/ Halley 1986. IMHO, Lovejoy is MUCH more spectacular and visible than Halley was at its best. However it is considerably less spectacular than McNaught was at its best. Overall – it is in the category of ‘spectacular’ comets. Commiserations to those in the northern hemisphere, who won’t be able to see this marvellous Xmas comet.

Dave Herald
Murrumbateman, Australia


From: Robert McNaught
Sent: Friday, December 23, 2011 5:56 AM
To: Comets-ml
Subject: Re: [comets-ml] Comet Lovejoy Spotted From Space Station

Confirming Dave Herald's comment on the brightness of the tail, I made it brighter than the surface brightness of the Small Magellanic Cloud (SMC) on Dec 21.7 UT, but comparable to the LMC. A more subjective comparison (again) would make it much more impressive than P/Halley in 1986 which I saw pretty much every night for over a month after perihelion.

Cheers, Rob

[Mongo]

Here is a cropped version of the full-resolution photo of the comet from the ISS:

[Mongo]

I like this shot, taken by Jim Gifford, it is very atmospheric:

[Mongo]

From comet-ml post #19031 by David Seargent:

Hi all,

At last, a clear morning here at Cowra. And the comet was glorious! tail was measured at 15 degrees, with the furthest portion dividing into a split main tail and a secondary emerging from the curving main one, giving the effect of a spreading triple tail. The main tail was judged to be about three quarters of a degree in width.

By contrast, the coma was very inconspicuous. In the 25x100 binocular telescope, a very rough estimate gave just mag. 5. However, saying that the comet was fifth magnitude gives absolutely no impression of the spectacle! The head was simply lost against the intense tail.

I had the strong impression that the central portion (in terms of length) of the tail was the brightest. The extremity was (not surprisingly) fainter, but the section closest the head was (more surprisingly!) fainter as well. At first, I thought that this was just the effect of lower elevation, however the impression continued as the comet rose higher, so I now think that it was at least partially real (although elevation no doubt contributed to some degree.) I recall that the same was true of Ikeya-Seki. In that instance, the brighter section was crossed by stria, however, I saw no evidence of stria in W3. Interestingly, with the naked eye, the tail seemed to wax and wane in intensity; an effect also noted in Ikeya-Seki. No doubt, this is simply due to waves in our atmosphere, but it nevertheless added to the spectacle.

There is no doubt that this comet is included amongst the Great Comets of history. Not the "greatest of the Greats" like Ikeya-Seki, Hyakutake, Hale-Bopp and McNaught, but certainly high on the list of the runners up!

Once more, congratulations Terry on this historic find. Your skill and dedication has been well rewarded!

David

[Mongo]

A great photo by Lester Barnes of south Australia:

[Mongo]

Commentary by John Bortle (comet-ml post #19037) on the photo just above this post, by Lester Barnes:

I am particularly taken by this latest image in that it almost precisely replicates images of Comet Ikeya-Seki from 1965. The match is nearly exact, right down to the distinctly brighter tail edges, the twists in the tail and even the faint outer sheath enveloping the bright dust tail. Such a feature was also seen in some of the drawings of the Great September Comet of 1882. Truly, Kreutz sungrazers are a group of comets absolutely unique unto themselves!

There seems to be some panic arising among folks currently experiencing cloudy skies down under, thinking that they may miss the whole show. Fear not, for as I pointed out previously although the comet's head will continue to fade rapidly, the tail will drop in brightness far more slowly. If it should follow the evolution of the tail of Ikeya-Seki, then the outer-most portion of the long dust tail will hardly fade at all over the next couple of weeks. However, the tail's middle section will, until it has faded to match the end portion. Then the entire tail will seem to fade as a unit. Remember too, that the tail will be continuing to grow throughout the period. I would anticipate the it might attain a final naked eye length of ~25 degrees, by which time it will be very faint and difficult ghostly specter to the naked eye.

I was interested to hear that David S. reports variations in the brightness of the tail over the course of a short time, a phenomenon referred to a coruscation. Such has been reported on rare occasions throughout cometary history. Although usually attributed to atmospheric instability, some instances have been much harder to explain as such and if seen, it should always be recorded, along with details of the prevailing weather conditions.

J. Bortle

[Mongo]

From comet-ml post #19038, replying to David Seargent's post:

I've been wondering when comet Lovejoy would earn the title Great comet and between your description and Lester's image, and all other images and reports from observers around the southern hemisphere, there is no question about it. The Great comet of 2011 it is.

Comet Lovejoy being a Great comet does imply another (very) impressive fact: just about any Kreutz sungrazer that does survive perihelion, even a small one, has the potential to become a Great comet. It only depends on the timing. So with a bit more luck then, both comet Pereyra and White-Ortiz-Boleli could have become Great comets.

[Mongo]

Another report on the comet by Geoff Dudley (comet-ml post #19039):

I went to The Briars (Mornington Peninsula AS HQ) down at Mt Martha yesterday morning 22Dec11, got there around 0340.

Greeting me were Rod Brackenridge and Greg Walton. Greg had setup 3 binocular chairs, an 8" SCT and 3 SLR cameras. I arrived prior to the comet rising so a very pleasant and comfortable time was had by all just generally admiring the sky, (which was beautiful and clear almost to the SE horizon)with 10 x 80's when at 0410 Greg said, "Someone's got a searchlight on over towards Hastings". He was right except for the fact that the beam was curved slightly northwards. I'd never heard of a curved searchlight beam and it wasn't moving about so it was then that we realised that it was the comet. It was easily visible, we didn't need binos. I stuck my hand out at arm's length and found that it just covered the comet so I guess the length was about 15-20 deg. We couldn't see a head, it may have been too low in the atmosphere. I had a look for comparison stars and took a punt on it being around mag 2 or 3. Very hard to work out with accuracy as the Sun was rising. The comet stayed visible even thru astronomical twilight.

Finally at 0444 we lost it.

Greg took lots of photos as his cameras were set to auto expose for around 10 secs each. He got a nice shot of the tail with a 120mm lens and when zoomed in clearly showed the split. It was a WOW moment.

Merry Xmas to all!

-- Geoff Dudley

One of the photos mentioned above:

[Mongo]

Now that Lovejoy is "officially" a Great Comet, I have decided to update the ranking of the Great Comets of the past several centuries that I had done here at the time of comet McNaught in 2007.

The point scale went like this:

MAGNITUDE: 10 points for every degree of magnitude brighter than +3 (dark-sky; daytime magnitude gets counted separately)

No points in this category.

TAIL: 1 point for every two degrees of length of naked-eye visible tail in dark sky

DURATION VISIBLE: 1 point for every month naked-eye visible in dark sky

The last confirmed report I read gave a tail length of about 28 degrees, for 14 points. I also assume the minimum duration of visibility of one month, for one additional point.

BONUS POINTS:
2 visible tails = 10 points
5 visible tails (West 1976) = 20 points
15 degree long anti-tail (Arend-Roland 1957) = 10 points
curved tail (Donati 1858) = 5 points
'bright' tail (Daylight 1910) = 10 points
'brilliant' tail (Ikeya-Seki 1965, Great September 1882) = 20 points
circumpolar all night (Hyakutake 1996, Tebbutt 1861) = 10 points
Mag. -3 in daylight (West 1976) or Mag. -5 in daylight (Daylight 1910) = 10 points
Mag. -8 in daylight (Great March 1843) = 15 points
Mag. -15 in daylight (Ikeya-Seki 1965) or Mag. -17 in daylight (Great September 1882) = 30 points

While currently fading, the tail was considered bright earlier, for 10 points, and it will be circumpolar all night after New Years Day, for another 10 points. It also reached about magnitude -4 when rounding the sun, for 10 additional points. There were definitely two visible tails, a dust dail and an ion tail, for 10 points. While its tail is curved, it was not curved strongly enough to gain more points. This may change as the viewing geometry changes.

Using these numbers, comet Lovejoy currently garners 55 points.

The updated list:

1861 123 pts Tebbutt
2007 105 pts McNaught
1882 101 pts Great September Comet
1910 95 pts P/Halley
1976 90 pts West
1996 78 pts Hyakutake
1997 73 pts Hale-Bopp
1858 68 pts Donati
1965 64 pts Ikeya-Seki
1970 61 pts Bennett
1957 57 pts Arend-Roland
2011 55 pts Lovejoy
1910 54 pts Daylight Comet
1811 52 pts Great Comet
1927 51 pts Skjellerup-Maristany
1843 50 pts Great March Comet
1874 46 pts Coggia
1881 42 pts Great Comet
1807 37 pts Great Comet
1853 37 pts Klinkerfues
1835 35 pts P/Halley
1957 35 pts Mrkos
1860 31 pts Great Comet
1911 29 pts Beljawsky
1911 28 pts Brooks
1819 25 pts Tralles
1854 24 pts Great Comet

Here is the same list in reverse chronological order:

2011 55 pts Lovejoy
2007 105 pts McNaught
1997 73 pts Hale-Bopp
1996 78 pts Hyakutake
1976 90 pts West
1970 61 pts Bennett
1965 64 pts Ikeya-Seki
1957 57 pts Arend-Roland
1957 35 pts Mrkos
1927 51 pts Skjellerup-Maristany
1911 29 pts Beljawsky
1911 28 pts Brooks
1910 95 pts P/Halley
1910 54 pts Daylight Comet
1882 101 pts Great September Comet
1881 42 pts Great Comet
1874 46 pts Coggia
1861 123 pts Tebbutt
1860 31 pts Great Comet
1858 68 pts Donati
1854 24 pts Great Comet
1853 37 pts Klinkerfues
1843 50 pts Great March Comet
1835 35 pts P/Halley
1819 25 pts Tralles
1811 52 pts Great Comet
1807 37 pts Great Comet

[Mongo]

As expected, comet Lovejoy is growing more prominent as the New Moon approaches, and as the comet itself gets nearer. From Vello Tabur in comet-ml post #19044:

Finally, I didn't have to drive too far this morning - only 30 mins out of Canberra to an old comet hunting location. My son and I arrived at 3 am and were immediately treated to a glorious sight upon stepping out of the car, with 2/3 of the tail already above the horizon. The comet seems brighter again, now that it is visible in a dark sky without moonlight interference. The brightest part (about 1/3 of the way along the tail from the head) easily outshines the LMC.

Got a few nice snaps too but I've only had time to put up this one:

[Mongo]

To make comparisons easier, I have put images of Ikeya-Seko (left) and Lovejoy (right) together. Lovejoy is clearly not as bright as Ikeya-Seki, but otherwise seems quite similar.

[Mongo]

The tail is getting bigger! From Rob Kaufman in comet-ml post #19045:

First clear morning here, and I was gobsmacked! It is huge, not quite McNaught scale but huge. I never saw the head rise because I have high hills around but I saw approximately 20-deg of tail emerge before it was finally washed out, first visually and then photographically.

[Mongo]

From Robert McNaught, comet-ml post #19047:

Despite a huge downpour of rain around midday, the humidity after midnight was sufficiently low that once the cloud passed, there was no fog or significant orographic cloud.

My initial impression as the comet was rising was that it was less bright than on Dec 21, leaving me a little disappointed. However once the full extent of the comet was visible, it continues to be awesome! Unlike Vello, I do suspect an overall fading, although it did appear to be a bit higher surface brightness than the LMC.

A scan with 10x50B really didn't show much structure, although the gas tail was more evident in the binoculars than to the naked eye. In 20x120B there is no sign of any condensation. Instead a little "spine" is evident (more on this later). The overall tail length from the photos is 21.7 deg for the dust tail and much the same for the dust. Averted imagination could make it longer, but I think lines of stars are being misleading.

So just what is happening at the heart of the comet? My interpretation, which I fully admit is from a position of ignorance, would be that there is an intact nucleus. This is based on the "spine" coming to a sharp point close to the the parabolic hood. If it were dissipating I would have expected the spine to be more diffused and for the parabolic hood to diffuse with it. There will be plenty of folks here that interpret the situation more reliably than me, but it certainly doesn't seem to be a Shetland comet ;-) (that's a Scottish joke).

Until tomorrow night.

Cheers, Rob

He also linked to several outstanding photos that he had taken:

[Mongo]

More confirmation of today's observations, by Chris W in comet-ml post #19050:

Hi all,

This morning i had to travel to a roadside spot between Nemingha and Loomberah (near Tamworth NSW) to view the comet. I arrived there at 3:50am AEDST only to find over half the comet has already risen!

At 4:20am AEDST i observed the comet's tail to be 22 degrees in length, the tail tip about 2 to 3 degrees in width and comparable in brightness to the Small Magellanic Cloud, the mid section between the head and "tail-split" about half a degree in width and comparable in brightness of the bar in the Large Magellanic Cloud. The comet head had no central condensation visible through 7x50 B's. The overall brightness of the comet appeared fainter than my previous observation 2 mornings earlier, the tail split was not as noticeable and the ion tail was hardly discernable.

[Mongo]

A response by Vello Tabur in comet-ml post #19055 to Rob McNaught's post #19047, two posts above this one:

Hi Rob,

It's quite possible that the comet has faded somewhat. My comments were relative to a reference point of two nights ago (Dec 21.7 UT), when there was still moonlight interference. I didn't see it the following night due to fatigue (I needed some sleep after racking up nearly 1000 km in the last few days). The view last night (Dec 23.7) finally had the comet reasonably high in a dark sky. Relative to 2 nights before, it was significantly easier to see with the naked eye and far more impressive. To my eye, it had transformed from a ghostly spectre to something of real substance. Having said that, I agree that the ion tail was less obvious and less structure was visible in the tail through binoculars. Overall -- still awesome!

Cheers,
Vello

[elakdawalla]

Mongo, I just want to say thanks for these summaries -- it's great to have a single, concise source for the latest comet visibility news! Though it's making me very jealous of our southern hemisphere friends.

[ElkGroveDan]

Mongo, I just want to say thanks for these summaries -- it's great to have a single, concise source for the latest comet visibility news! Though it's making me very jealous of our southern hemisphere friends.

Ditto. I've been thinking about driving to Argentina. It's only 6451 miles.

[Explorer1]

That would be rather tricky, considering the Darien Gap...

[Mongo]

Christmas Eve image of comet Lovejoy by Scott Alder:

[nprev]

W O W ! ! !

[Mongo]

Yes, I think that Lovejoy has done quite well for a comet that was not supposed to survive perihelion.

[Mongo]

From comet-ml post #19078 by David Seargent:

I thought that the tail was somewhat less intense but longer than on the previous 2 mornings and the head (which was very indistinct and essentially just a lower terminus of the tail) about magnitude 4.8. By the way, the 15 degrees I gave as the tail length for Dec. 21 should read 21 degrees. I left out a term in the formula used for calculating angular distances on the sky (OK, math was never my strong point. If it had been, I probably would have studied Physics instead of Philosophy and become a professional astronomer!). In any case, this mornings tail length was measured as 28 degrees.

The length, shape and general morphology of the tail looked very similar to that of Ikeya-Seki when observed the same number of days after perihelion. Yet, I-S was definitely more intense; I would guess from memory about 2 magnitudes brighter. Also, the terminus of the tail seemed to end more suddenly than that of Lovejoy (the last 5 degrees or so of W3's tail grew very faint and difficult with the naked eye and could not be traced in the telescope). But the biggest difference was the head. At this point in its orbit, the head of the earlier comet was also about 2 magnitudes brighter and appeared in the 20x65 binoculars that I was then using as a very distinct, almost disk-like object; rather like a very bright and compact planetary nebula.

[Mongo]

From comet-ml post #19088 by Robert McNaught:

On Sun, 25 Dec 2011, [iso-8859-2] Jakub Èerný wrote:

> Actually I do not think that nucleus has dissipated. Activity just fade
> quickly, but apparently there is still something huge producing much more
> material into tail and coma, unlikely swarm of debries.

Thanks Jakub,

I tend to agree that there is an "invisible" mass responsible for the hood and spine. The tail is showing no signs of becoming a ghost. I've put up a processed Uppsala image from last night (Dec 24.7UT).

http://msowww.anu.edu.au/~rmn/C2011W3.htm

It continues to show a well defined parabolic hood and the spine narrowing basically to an "empty" point pretty much on the edge of the parabola. Trying to image it now, but there is cloud and I can't get a focus sequence.

My astrometry of the tip-of-the-spine will perhaps tell one way or another whether this is a substantial mass or displaying significant short-term non-gravitional effects. Give it a week and we should a good handle on the dynamics.

The tail continues to fade (Dec 25.7UT) and is very significantly less bright than on Dec 21. There was quite a similarity to Hyakutake tonight, partly due to the tail being so long, narrow and "ghostly". There is no real comparison though, as there is no coma and condensation, which were both prominent in Hyakutake. On Dec 21 though, the tail surface brightness was sufficient to put it in the "awesome" category for me. Very much on par with Hyakutake, Hale-Bopp and Bennett. Tonight it was much more Halleyesque. I'll reply to the great comet listing thread in a day or so as I've been keeping such a list (and noting other folks lists) for a couple of decades.

[Mongo]

Comet-ml post #19096 by Rob Kaufman:

Here's a rough composite showing the growth of Lovejoy over the last 4 days, using some images kindly lent to me as I've only had one fine morning to observe it since it hit dark skies again. The various images were resized to the same scale. Don't place too much credence in the actual degree length stated as there are lots of variables that determine how much will be showing in any particular image. For this morning, the 30-degree tail length is based on several photographs that appear to show very faint extensions out to that length.



Anyway, the massive expansion is pretty clear. Hoping to get another great view of this 'megacomet' in the morning.

Cheers -

Rob Kaufman
Bright, Vic, Australia

[Mongo]

Comet-ml post #19100 bt Dave Herald, regarding the visual brightness of comet Lovejoy:

IMHO, most of the images that have been posted over the last few days reflects the true visual appearance. Specifically, in dark skies you can see the tail to the same extent as is shown in the images.

The main issue is how you might represent the brightness of the comet's tail. I think the best way to describe this is that the comet is currently close to one of the brighter parts of the Milky Way, and compared to the milky way at the same altitude, the surface brightness of the majority of the tail is somewhat brighter than the brighter parts of the Milky Way.


Dave Herald
Murrumbateman, Australia

[Mongo]

Comet-ml post #19101 by Rob Kaufman:

Hi Frans. I can only speak for the 23rd (24th here), but the visual view was very much the same as the photograph shown in the composite. In darker skies the tail was quite bright and prominent. I made out 20 degrees of tail visually, but didn't see the head or last couple of degrees of tail rise because daylight washed it out. The ion tail on the 23rd was quite prominent visually and the extent of faint end of the tail visible matched the photograph quite well.

Cheers -

Rob

[Mongo]

From comet-ml post #19115 by Jim Gifford:

As the comet's tail rose tonight it was at first hard to pick against the Milky Way background. The higher it rose the easier it became because of the straight edges of the tail. It has faded considerably since I observed it last on the 24th December but is now much longer at 28 degrees. It became striking to observe only when its full length was above the horizon and it stood vertically below the Southern Cross. All the intensity has gone out of the head and tail.

[Stu]

Latest ISS shots put together...

[Mongo]

From comet-ml post #19117 by Rob Kaufman:

Nice report Jim. I too observed it this morning, starting earlier at 1:30am (UT+11) with a fair bit of the fainter tail showing. I had also observed it on the 24th (23rd UT) and this morning it was considerably fainter, and longer. I could imagine that now, combined with interference from the Milky Way, it might be difficult to see in light-polluted skies. Nonetheless, I found it quite impressive still from my very dark sky site. Gone are the 'ribbon' structures and the ion tail evident on the 24th, and the tail (naked-eye, binoculars & photographic) shows no structure. The tail appeared fairly bright for the first 10-deg or so, but naked eye the exact position of the head was difficult to make out as the tail narrowed down to nothing. Not so with binoculars or photographically.

As the tail fanned out the surface brightness diminished although it was quite clear as far as the top Pointer, a distance of 28-deg. Naked-eye I could make it out faintly to halfway between the top Pointer & the Southern Cross, about 33-deg. Nothing could be seen there with binoculars - in fact even the section adjacent to the Pointers was difficult to make out with binoculars. Photography seems to show some faint hints of dust extending to adjacent to the Cross (perhaps 38-deg) but I need to check some reference images to see if it's just fortuitously aligned bright patches.

Was it John Bortle who predicted the comet would expand & dim to became a huge 'ghost'? Because that's the impression I got. The comet would still be a striking sight away from the Milky Way, but even in amongst it I found the sight of this great ghost transfixing, a true wonder!

He also posted this image:

[Mongo]

Comet-ml post #19119 by John Bortle:

--- In comets-ml@yahoogroups.com, "Rob" <Rob.Kau@...> wrote:
>
> Was it John Bortle who predicted the comet would expand & dim to became a huge 'ghost'? Because that's the impression I got. The comet would still be a striking sight away from the Milky Way, but even in amongst it I found the sight of this great ghost transfixing, a true wonder!
>
> Rob Kaufman
> Bright, Vic, Australia
>

At this time I would hasten to point out that based on descriptions of the Post-T evolution so far, 2011 W3 is almost precisely mimicing the physical appearance of the Great Southern Comet of 1880 during it apparition.

If this continues I would predict that by about next weekend 2011 W3's tail will have assumed essentially the same low level of brightness over virtually its entire length. As it fades toward obscurity, it will attain a maximum length between 50 and 60 degrees as seen from the darkest observing sites, but be exceedingly faint and ghostly in its appearance. At the same time the head will fade way completely, the sunward end of the tail simply fading to nothingness against the sky.

Incidentally, my main computer is down and I'm working from a tiny and frustrating laptop, so please forgive typing errors. I'm also unsure just how much I will be able to participate on the forum this week until my big machine returns.

J.Bortle

[Mongo]

Comet-ml post #19122 by David Seargent

Hi all,

This morning (Dec. 26, 1600-1650 UT) about 37 degrees of tail could be seen from Cowra, reaching up to the outer edges of the Southern Cross. Interestingly, this was the first time that something that could be called a "head" was discernible in the 25x100 BT. At the end of the tail, there was a small (approx 4 arcmin) very diffuse, transparent nebulous blob slightly brighter than the adjoining tail (m = 5.3). The distinction between "head' and "tail end" was more apparent using averted vision, but it was truly there! The two earlier sungrazers that I saw developed in a similar way, albeit much later after perihelion. Ikeya-Seki about 7 weeks after perihelion and White-Ortiz-Bolelli about 3. I would guess that the early diffusing of 2011 W3 probably signifies a small comet shutting down whilst still closer to the Sun rather than one that is disintegrating. On the other hand, the tail (although much fainter) is still very distinct and remains impressive in a dark sky. The length is truly amazing ... lengthening even while it fades!

Cheers,
David

[Mongo]

Comet-ml post #19122 by Vello Tabur

Hi,

I concur with the descriptions provided by others this morning. Although the comet has faded significantly, it still remains an easy naked eye object. From a dark-sky site near Boorowa, NSW, the tail was fainter than the nearby Milky Way and is now only slightly brighter than the SMC. There is no sign of the ion tail and the dust tail appears slightly narrower than on my last observation 2 days earlier. Visually, I could only trace the tail to the same altitude as midway between alpha/beta Centuri but, the wide-field image below hints at a continuation toward Crux, as noted by David S.



Vello

[Mongo]

From comet-ml post #19128 by Michael Mattiazzo:

The tail is noticeably fainter than 2 mornings ago, however it is still growing as the comet approaches Earth. Closest on Jan 8 at 0.5AU. The tail is seen visually for 30 degrees, extending to near Beta Centauri. This photo shows a fainter extension out to 38 degrees! The first 10 degrees of tail is still relatively bright, comparable to the norma starcloud.

[Mongo]

A spectacular image hosted on Gary Kronk's Cometography website. Photo taken by Gordon Garradd on December 22:

[Mongo]

Comet-ml post #19131 by Andrew Pearce:

Hi all

I finally observed this wonderful comet from a very dark sky site in northern Victoria (Lockington) Australia. The tail now extends almost to the Coalsack nebula. I measured it as 30.0 degrees on Dec 28.74UT. What is most striking about it is it's extreme straightness. For all the long tailed comets I've observed there always appears to be some degree of curvature but not so with C/2011W3. The surface brightness is fainter now and would be a struggle to see much in a light polluted area but it is very impressive from my current dark sky site. To the naked eye, the head of the comet is virtually non existent and I'm not sure there's a lot of value in a coma total magnitude estimate.

Regards
Andrew Pearce

[Mongo]

Comet-ml post #19142 by Andrew Pearce

Hi All

The tail surface brightness is decreasing every day and as Rob mentioned, whilst it is visible with direct vision it is not easy. With averted vision however it is quite distinct. On Dec 29.73UT I measured the tail length as 32.0 degrees. It now extends almost to Alpha Crucis and can be faintly seen crossing the southern edge of the Coalsack nebula. It would be difficult to observe a longer tail than that visually as the line of the tail past Alpha Crucis extends into an area of the Milky Way which is very bright and the tail would be difficult to discern in this area and that will probably be the case over the next few mornings. The last 10 degrees or so of the tail is quite vague and ill defined in comparison to the first 20 degrees which is still quite narrow and very straight.

I'm leaving the dark country skies today so this will be my last observation but it's been a fascinating last week!

Regards
Andrew Pearce

[Mongo]

Comet-ml post #19150 by Chris:

Hi all,
I observed this morning from 20kms East of Walcha, i also tried around 10:30pm on the evening of 30th Dec but moonlight washed out the tail in the background sky.

The tail was dimmer than SMC and slightly fainter than the Milky Way area just below the Pointers, i traced the tail to 22 degrees with the naked eye, which was just past Beta Cen, the eastern side of the tail end seemed to curve slightly to the East, the Western side appeared realtively straight.

There was a gap between the Milky way and the tail mid section which helped locate it with naked eye.

With 7x50 B's the head of the comet was 15' in dia, the width of the tail in the mid section was around 2 degrees, and fanned out to around 3.5 to 4 degrees at the end.

I did get a mag estimate but need to get to my program which is at work.

Cheers,
Chris W

[Mongo]

From comet-ml post #19154 by Michael Mattiazzo

The visual tail length with the unaided eye has reduced to 17 degrees, traceable to Alpha Circinus and photographically about 25 degrees. The bright milky way is interfering with the view.

The tail is continuing to fade with each passing morning and is now of similar surface brightness to the SMC.

Thus probably not observable from light polluted city skies.

Whether the reduced tail length is real or not, we will need to wait a few more days for the comet to move away from the milky way.

[Mongo]

Comet-ml post #19169 and #19174 by David Seargent

Hi All,

The tail has cleared the brightest part of the MW and this morning (Dec. 31. 1600 UT) I'm sure that I could trace it with averted vision into Carina; a length of (wait for it!) 45 degrees! The sky was very clear with a limiting naked-eye magnitude of around 6.5 or better.

Cheers,
David

Hi Rob and all,

Yes, I did put down a couple of wrong numbers (lack of sleep I guess). Still, it does not make a very great difference. The revised length comes out at 39 degrees ... and this time I checked the numbers! The end appeared to be near Theta Carinae, visible with averted vision only in "flashes". Perhaps it was averted imagination, but I think it was real.

Cheers,
David

[Mongo]

Comet-ml post #19176 by John Bortle:

By physical necessity and as I've pointed out previously, the dust tail of 2011 W3 SHOULD be continuing to lengthen...at least until the surface brightness of the outermost portions drop completely below the detection limits of the method being employed. For the unaided eye I'm afraid that this will occur fairly soon. However, for appropriately long exposed, highly processed, fairly small-scale images this interval should be considerably extended.

If astro-imagers familiar with the sorts of image processing done to bring out the absolute threshold details in such objects as galaxies apply their techniques to appropriate images of the comet I see no reason for the ultimate length of the tail not turning out to be something in the order of 50-60 degrees by mid January. I know that years ago when I dabbled in this area I could bring out details far beyond what I ever imagined were in the original images (although the pictures no longer were very pretty to look at!)

J.Bortle

[nprev]

Just heard from my stepdaughter, who returned today from a holiday hiking vacation in southern Chile. Although she's not an astronomy buff, she said that the tail very much resembled a searchlight beam a few days ago so it must have been quite spectacular. One of her fellow travelers apparently acquired a great shot, so hopefully I'll get a copy & be able to post it in a few days.