LASCO C3 and SECCHI COR2A
I have tried to find SOHO-1241 in the COR2A images, but without success...
SOHO-1241 was found by Bo Zhou in C3 images of 2006 December 21. It was one of the brighter Kreutz group comets in December and entered the C2 field at about 03:00 UTC on December 22.
Animation from five C3 images 2006 December 22
00:18 - 02:42 UTC (original scale).
In the first frame the comet is close to SAO 186235 (mag 7.2).
At lower left is NGC 6553 above SAO 186362 (mag 7.7).
NGC 6553 is a globular cluster (mag 8.1, diameter about 3').
The comet's magnitude is about mag 7.
I have enlarged the C3 images four times to match the scale of the COR2 images (about 14"/pixel):
I have rotated five COR2A images from 00:03 to
02:33 UTC by 22 degrees clockwise to match the orientation of the
C3 images:
While more stars are visible in the COR2A images and NGC 6553 looks really bright with mag 8, SOHO-1241 with mag 7 is absent.
Karl Battams wrote (Sohohunter List, 2006 Dec
19, #2024):
Re: STEREO "First
Light" press release
--- In sohohunter@yahoogroups.com, "Grei Lar" <grei13@...>
wrote:
> So Karl, have you been nosing around the STEREO images to
see if you can
> spot any of the comets we've been seeing with SOHO? ;)
Yes I have (and no I haven't seen any)! There was a reasonably
bright
C3/C2 Kreutz on the 12th (?) that should have been visible in
COR2
images but I could not find it. Possible reasons for this are: 1)
We
needed a slightly longer exposure time 2) I wasn't looking in the
right area (although it should have been obvious) 3) the images
were
at a 1hr cadence so maybe it just moved too fast and I missed it
4)
the comets are not going to show up well in the COR images.
Unfortunately, #4 is a definite possibility as the COR images are
polarized and also (from what I have been told) the sodium lines
(which the Kreutz comets show *very* strongly in LASCO) will not
be
visible in the COR images. So don't go getting your hopes up too
high...
~~Karl
It seems that "4) the comets are not going to
show up well in the COR images." is true. I have found the
spectral range for the COR1/2 images as: 650 - 750 nm. The sodium
lines are at 589 nm and not in this spectral range. That's bad
for the Kreutz comets, but other comets could show better.
Rainer Kracht, 2007 January 05
I have added an animation with images aligned
on the stars:
2007 January 06
After I have found a bright C3 Kreutz comet in COR2A images of 2007 February 01, I'm convinced that the last frame of the animation above shows SOHO-1241. You can see a comparison of the images here.
2007 February 05