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A day of M94(NGC4736), The ‘Cat’s Eye’ galaxy.

RobH

By RobH
in Imaging - Deep Sky

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RobH

RobH

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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 away.

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 red channel.

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 faint.

For some reason, no dark matter surrounds this galaxy.

Big image here....

http://middlehillobservatory.co.uk/IMAGES/Full%20size%20pics/M94-LRHaGB%20MASTER-framed.jpg

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.

Cheers

Rob

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yeti monster

yeti monster

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Lovely work there. I'm really beginning to appreciate the effort involved in producing these images. Well done.

M94 is ear marked as a potential target for my fuzzy hunt in April, although I know I'll not see anything near this sort of detail and clarity.

You imagers take us visualists so much nearer to the heavens.

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RobH

RobH

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Thankyou folks :)

Looking at it today, I reckon the stars need a tad more saturation, so I'll post another version after I've taken the hound for his afternoon swim in the sea ;)

Grabbing enough data for the outer ring was a real good example of the fact that sometimes aperture rules....my 6 inch scope is as good as they get, but it's still only a 6 inch, and to really go at the ring properly a bigger one is needed. I do have a 10 inch ordered, but this may well have prompted me to get a really big lightbucket too....14 or 16 inches probably :)

Cheers

Rob

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ollypenrice

ollypenrice

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A masterpiece. The layering is seamless and the whole smoothness of the image, despite its faintness in places, just oozes quality. Truly exceptional.

BTW I have just done NGC4725 which has also been reclassified from ring into one-armed spiral. That would be a lovely target for your 10 inch when it comes becuse there is an exquisite little spiral just next door. I won't post mine because it is Martin B's baby really.

Olly

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Psychobilly

Psychobilly

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This is one "deep" image...You have blown away my CDC catalogs with this one Rob...

I run out of stars around mag 16.2 and there are galaxies in there that arent in the version of the PGC catalog that I have loaded...

Only have 4 definites in there so far PGC 3551865, 3551847, 2174346 and 3551865...

The large edge on galaxy in the bottom right doesnt even appear on the charts...

Peter...

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Tim

Tim

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Superb Rob. For me, this is your best image to date, and considering its stablemates, that makes is something special. Those background galaxies are fantastic, and a great backdrop for the main feature.

Tim

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RobH

RobH

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Thanks Tim.....Wavelet tool eh?

Fascinating....I look forward to a demo ;)

I've tweaked the star colour a little...a subtle difference but it improves it I think.

Cheers

Rob

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