M94(NGC4736), The 'Cat's Eye' galaxy.
I find these ring type galaxies particularly beautiful.
This one was discovered by Pierre Mechain (he seems to have discovered
everything!) on 22nd March 1781, it lies in Canes Venatici, near the star
Cor Caroli and is thought to be anywhere from 15 to 30 million light years
It has a very high dynamic range, much more so than M42 for example,
meaning that there is a really big difference between the brightest and
darkest regions, so it's very easy to burn out the core and central detail
when trying to bring out the faint stuff.
The core of M94 is really bright, the immediate surround a lot less so,
and the outer ring is incredibly faint and needed hours of long subs to
bring it out.
The core is made up of 60 second subs which were then dropped into the
surrounding image, and lots of careful stretching and masking using layers
has been done.
Capturing enough data for the outer ring was a long job
.I shot about
4 hours or so, and did a quick process, but couldn't stretch it far without
noise becoming an issue, so just kept adding more and longer subs until
it was useable.
I could have stretched the surrounding ring more, but even after over
15 hours of luminance data, it would have become noisy, so I left it where
it is and hopefully kept it looking natural, and am happy that I've managed
to catch a bit of detail in the region. I may well throw some more time
at it next year.
This is a 'starburst' galaxy, meaning that it has active regions where
star formation is occurring very actively. These are thought to be caused
by gravitational pressure waves. The main one can be seen as a ring of
red around the centre, which I highlighted by adding H-alpha data to the
Until recently, it was thought that M94 was a classic ring galaxy, but
it's now known that the outer ring is actually spiral arms, just very
For some reason, no dark matter surrounds this galaxy.
| Click on image below
for full size version
Imaged on 10,11,13,19 & 28th February & 10,13,14,15th March 2010
from Dorset with a TMB152 @ F8 and Atik 16HR.
Luminance. 27 x 10 minutes
2 x 15 minutes
31 x 20 minutes
Red. 18 x 6 minutes
7 x 10 minutes
Green 20 x 6 minutes
Blue 18 x 7 minutes
5 x 10 minutes.
Total imaging time. 23 hours 23 minutes.