[X] My Assistant

[TheAnt]

I agree with Mongo, what we see do not follow the ordinary rule for a cometary tail, but fans of has and dust created by geyser like eruptions - the result of significant heating. Perhaps also freshly exposed areas, it might be pushed into a regular tail later on but things have changed very fast here.

@craigmcg: Yes it really looked weird when I had a peek at some sites myself. Yet our friend at the Comet ISON 2013 UK site have at least updated his site now.

[Mongo]

A nice image from NASA, located at this page:

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[dilo]

ISON on SDO (AIA 193):

Mongo, pls, where did you got the image/info?

[Mongo]

Mongo, pls, where did you got the image/info?

It was linked to on comets-ml, the original image (as I just found out now) is at Spaceweather.com realtime image gallery image page: Comet ISON Perihelion AIA 193 Kiosk

[Explorer1]

Official SDO twitter says they couldn't find it yet. Maybe it was just a (very) ill-timed glitch.

[dilo]

It was linked to on comets-ml, the original image (as I just found out now) is at Spaceweather.com realtime image gallery image page: Comet ISON Perihelion AIA 193 Kiosk

Thanks, this is a bightened version and author says "possible shot of ISON, hopefully, more an likely a glitch, only in one frame". However, it appear compatible with object I recognized in the two frames from AIA4500...

[fredk]

The C3 view here is presently unclipped. Here's a processed (high pass filtered plus stretched) version:
Edit: improved version posted below.
ISON is about halfway below centre. For comparison, Antares is the brightest spot roughly opposite the Sun from ISON.

Not being clipped, it should be possible to get a reliable magnitude estimate - but this is a job for those familiar with comets and SOHO.

[Mongo]

A combined graphic (put together by @CometISONnews) of SDO images that show specks that might be ISON. Obviously, they cannot all be of the comet. And the one I had linked to, timestamped 18:28:31, is not on the graphic. I would not be surprised if several of these spots are indeed of ISON, but which ones? A trajectory of ISON with times, as seen from SDO, is needed for comparison.

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[fredk]

Improved processed version of the unclipped image. This now shows M4 (faintly) for comparison.

[machi]

I don't know exact geometry for trajectory of ISON on SDO images, but those three specks looks like they are on the same trajectory and distance between them correlates with time.

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[Ant103]

For me, it's just hotpixels. Nothing more to be seen here. If this were a comet, it should be more blurry. IMHO.

[dilo]

For me, it's just hotpixels. Nothing more to be seen here. If this were a comet, it should be more blurry. IMHO.

Yes, they appear as "single" hot pixels and also the 3 ones highlighted by Machi do not match a curved "expected" trajectory...
The two objects highlighted be me in the visible channel, on the other hand, have a completely different aspect; I tried to make a mosaic with them:

compared with the other mosaic reported by Mongo, their positions are different. I am aware that Sun luminosity should be greatly exceeding light scattered by comet nucleus/coma, this make me sceptical also toward these strange features...

[Mongo]

Emily Lakdawalla put together this short video of ISON rounding the Sun, as seen by the STEREO-B spacecraft:

animated GIF

It's starting to look like a more conventional comet in the last few frames.

[TheAnt]

.....It's starting to look like a more conventional comet in the last few frames.

Indeed it does, a few hours after Perhelion we can see some major outgassing and dust yet after some 7-8 hours ISON had re-grown tail facing away from the Sun again.
And more nice images coming up on The Spaceweather site.

[scalbers]

I don't know exact geometry for trajectory of ISON on SDO images, but those three specks looks like they are on the same trajectory and distance between them correlates with time.

My updated ephemeris here has some geometric info. It has Declination, Right Ascension, Elongation, and Tail Position Angle (a proxy for azimuth offset from the sun). They are listed every .02 days of UTC. I suppose the listed elongation may be a bit imprecise to the nearest tenth of a degree, though perhaps it would help constrain things. Maybe I can change that precision when I rerun this next.

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

Offhand, the 18:31 image should be pretty close to the time of minimum solar elongation, so it's hard for me to see how any combination of the dots would fit the trajectory.