[X] My Assistant

[bkellysky]

Good article on line at Sky and Telescope with updated prospects for Comet ISON by John Bortle

http://www.skyandtelescope.com/observing/h...-211408441.html

Seems like a reasonable assessment, including accounting for the less-than-predicted brightness seen just before solar conjunction.

[scalbers]

Nice article by John Bortle who has so much experience with comets. Good points about the tail being visible after perihelion with a fading head. FWIW, the latest formula I'm using for ISON also has a -6 magnitude peak. Being -6 would be insufficient for naked eye visibility at perilhelion - compare with Ikeya-Seki near mag -14. This light curve also keeps it more like magnitude 5 during mid-November, so in that case it likely wouldn't be visible naked eye if twilight glow is accounted for. Thus I'll be keeping binoculars handy to see this.

[TheAnt]

Astronomy now got this update on ISON

[scalbers]

I'm continuing with a light curve and visibility calculation that has it a bit fainter than naked eye threshold in mid-November and throughout the apparition.

http://laps.noaa.gov/albers/ast/eph/ISON.2012S1.co.html

http://laps.noaa.gov/albers/ast/eph/ISON_h....2012S1.co.html

[dtolman]

I'm continuing with a light curve and visibility calculation that has it a bit fainter than naked eye threshold in mid-November and throughout the apparition.

http://laps.noaa.gov/albers/ast/eph/ISON.2012S1.co.html

http://laps.noaa.gov/albers/ast/eph/ISON_h....2012S1.co.html

ISON is now at magnitude 6 and brightening - a two magnitude jump practically overnight:
http://www.isoncampaign.org/Present

[Mongo]

I love this image taken by Damien Peach on November 15th with a 20cm telescope (click on thumbnail for larger image):

[nprev]

Absolutely stunning. I am growing cautiously optimistic about the post-perhelion apparition.

[Mongo]

Second Major Outburst in Four Days

As I am sure you already know, ISON underwent a major outburst peaking on November 15th, which gradually declined over the next several days. It appears that a second, even larger, outburst is under way. The chronology of events as posted at comets-ml:

From ejehin on Nov 13

TRAPPIST : ISON outburst !
Dear all,
Very good news, TRAPPIST ISON production rates (all gas species) have been x2 in only 24 hours !
We now reach about 2E28 mol/s for Q(OH) at 10.000 km.
It looks like an outburst is going on, as the increase was not as fast the last 4 nights,
We now see also jets in OH bands same location as those of CN and C2.
AfRho from dust continuum is only rising a bit,
R and V broad band flux have also increased by factor 2,
We should be able to get images until Nov. 18, but window is only 20 minutes now and comet below 15 deg,
Clear skies,
Emmanuel Jehin

From biver_nicolas on Nov 14

RE: TRAPPIST : ISON outburst !
ISON is visible to the Naked Eye!!
Just 40min ago before clouds came in again (it snowed here yesterdy evening), I saw ISON with naked eye and adverted vision (good dark sky from Pico Veleta, SQM=21.14 to 20.9 in the zodiacal light).
It is about m1=6.3 to 6.5, estimated from naked eye and binculars (nearly starlike).
I saw it quickly in the Celestron 8, very condensed and hard to make out a structure, but the beginning of the tail does not look (yet) much brighter than the days before.
(I estimated ISON to m1=7.4 yesterday 13.22-Nov and 8.1 on the 12.2-Nov.)
Nicolas

From ejehin on Nov 14

TRAPPIST update : major outburst ongoing !
Dear all,
We had a hard time this morning to observe ISON, which is lower and closer to the Sun, but it was so bright we are saturating the broad band filters in 10s and plenty of flux in 20s with the narrow band filters.
To our suprise the change has been huge in the last 24 hours ! We are reaching 1E29 mol/s in OH, an increase close a factor 8 of the amount of gas released in space, since 24 hours !
The AfRho has also increased by the same factor (it is now 2400cm), so dust is finally released too, even if the level stays quite low compare to other comets.
Two jets are now also visible in OH band (coming from water dissociation) and also faint ones in the dust continuum at the same position as the CN and C2 jets previously reported.
There is no indication yet of disruption, the inner coma is very sharp (4 arcsec) and round in the dust continuum windows and there is no other special features in the coma.
This is the early phase of the outburst as the dust is still close to the nucleus and we should still expect a large increase of the magnitude and the coma diameter if more dust is released in the coming days.
The comet will become rapidly visible naked eye if the outburst last a few more days !
Best regards,
Emmanuel

From e48d5e092c3a74bb8dc8987a056172ad on Nov 14

Comet ISON (C/2012 S1) From Pasadena CA
I observed comet ISON from Pasadena, CA this morning, 16 minutes after the start of astronomical twilight, sun elevation -14.6˚. Scattered cirrus was present as was suburban light pollution. I used a 70mm refractor at 20X, timed the drift of the coma to measure the diameter, and used the Beyer method of magnitude estimation with TK reference stars:
2013 Nov. 14.552 m1=5.8, Coma dia.=1.25' DC=7
The coma was circular and well defined, of a deep blue-green color and the central condensation was bright and nearly starlike. It resembled a circular planetary nebula around a central star as seen through a giant telescope.
The tail was not seen.
Yesterday (11-13-2013), ISON appeared ghostly in the same equipment. This morning, it appeared the same size, but bright and easy to see!
Anthony Cook
Astronomical Observer
Griffith Observatory

From Man-To Hui on Nov 15

Dramatic Morphological Change of C/2012 S1
Hi all,
We (Quanzhi Ye, Man-To Hui and Xing Gao) noticed a dramatic morphological change of comet C/2012 S1 (ISON) observed via the 0.35-m f/6.9 Schmidt telescope + unfiltered QHY9 CCD at Xingming Observatory C42 from Nov 13.99 UT to 14.99 UT. Seven delicate (plasma) tails are visible from P.A. 275 to 320 deg (0 deg at north) in the Nov. 14 images. In comparison there were only two obvious in the Nov 13 images. After applying the azimuthal median filter to images from both dates, we saw two intense jets in P.A. 0 deg and 220 deg in the Nov 14 images, both slightly skewed to the anti-solar direction and measured ~34-arcsec in length. The two jets were absent in the Nov. 13 images. Images could be found at http://flic.kr/p/hyyTwX (Nov 13) and http://flic.kr/p/hyyUhK (Nov 14). What we found has been reported to CBET.
Cheers,
Man-To Hui (Cantonese)
Wentao Xu, Wen-Tao Hsu (Mandarin Chinese)
Astrosite: comethunter.lamost.org
Blog: pachacoti.wordpress.com

From Jakub Cerny on Nov 15

Re: Dramatic Morphological Change of C/2012 S1
Hi,
very nice report!
Missing presence of any synchronic feature inside coma ruling out any disintegration process. The jets looking like health turn-on of nucleus, which remaining mostly intact.
Best regards,
Jakub Cerny

From ejehin on Nov 19

TRAPPIST ISON update : new outburst !
Dear all,
Since our last report and major outburst on Nov. 14, the ISON production rates were dropping. We lost about a factor 2 in all measured quantities in 4 days.
No sign of breakup in the images.The dust features in our pictures seem to be linked to the active regions identified earlier in C2 and CN.
But this morning 19.37 Nov UT, we found ISON very active again !
All the production rates have been x ~6 since last night, while the AfRho, maesuring the quantity of dust, was only x ~2.
This looks to us to be the start of a new outburst linked to the active regions, as the jets are today strong again.
Our campain is unfortunately nearly over with TRAPPIST, but we will try to point it again the next couple of nights and confirm this new rise.
Is there new visual estimates ?
ESO picture of the week : http://www.eso.org/public/images/potw/
TRAPPIST news : http://www.orca.ulg.ac.be/TRAPPIST/Trappis...News.html#new25
Cheers,
Emmanuel Jehin

[MahFL]

I am going to try spot it tomorrow am, skies are currently clear.

[Mongo]

Thumbnail linking to Twitter image of ISON taken November 15 by H. Hanayama & H. Fukushima with a 105cm reflector:

[Explorer1]

A realtime gallery of the comet from spaceweather.com

http://spaceweathergallery.com/index.php?title=comet

[Ant103]

Here it's cloudy, and will be cloudy for the whole week… I will not have a chance to spot this comet

But this is gonna be exciting to follow

[MahFL]

Cloudy in NE FL .

[Mongo]

From Sky and Telescope's Latest Updates on Comet ISON for this morning:

Even as ISON drops lower every morning at the beginning of dawn, it's now brightening fast. This morning it was immediately obvious in my 10×50 binoculars through the moonlight and suburban light pollution: a fuzzy "star" with a hint of tail, bright greenish white and showing a tiny, starlike pseudonucleus. The comet head was much brighter than 5.5-magnitude 86 Virginis 3° above it.

Vitali Nevski, ISON's co-discoverer, estimated it at magnitude 3.7 this morning in Russia. John Bortle in New York State called it 4.8 but was nevertheless struck by its new brilliance. He writes:

I was amazed at its intensity as seen with my 15x70s. This morning C/ISON reminded me very much of the way Ikeya-Seki looked during one of my last pre-perihelion sightings in early October of '65.

Once clear of the trees, with twilight already having begun, it was surprisingly bright with an intensely condensed coma roughly 2.5′ in diameter. Total magnitude after accounting for atmospheric extinction was 4.8, although in my opinion the available comparison stars were less than first class, most for lack of choice being of spectral class K. The comet could be easily followed in binoculars long into twilight... a good sign for things to come! No tail clearly evident against the twilight sky.

For comparison, Lovejoy was at magnitude 9 at eight days before perihelion, and ended up peaking at around magnitude -3.

Assuming that ISON does not disintegrate in the coming days, we could be in for a truly spectacular sight after perihelion, with it becoming significantly brighter than Lovejoy at its best.

[ElkGroveDan]

Thanks for these updates Mongo.

I thought I might get one last look today before the moon steps on her but we had clouds and rain this morning. Here's my effort from Nov 15 a cropped five image stack taken with a 250mm lens on a static tripod. After that the clouds moved in.

Attached thumbnail(s)