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Old 28-10-2011, 06:18 PM
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NGC908 a rarely imaged pretty spiral galaxy

Carrying on with imaging galaxies, I found this one was at a good spot to image at the moment.

Quite small and faint it has a nice shape to it.

Planewave CDK17 at F6.8, FLI Proline 16803, Paramount ME mount.
MMOAG guiding with ST402.

http://upload.pbase.com/image/139206574

Greg.
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Old 28-10-2011, 06:44 PM
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A pretty little thing, Greg!
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Old 28-10-2011, 07:31 PM
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Indeed a lovely image Greg. You are going off the beaten track for some excellent results.
NGC908 has had 2 recorded Supernova 1994ai Williams & Martin (Perth Automated Supernova Search) @mag17 type 1c & SN2006ce @mag12.4 type 1a Monard ( South Africa).
It's about 65 MLY years distant.

Here is a nice little group worthy of the GregBradley treatment
NGC92 & 3 other galaxies AKA ROBERTS QUARTET RA (2000) 00:21:31 DEC -48:37:29 MAG12.9. NAMED AFTER ROBERT FREEDMAN WHO CORRECTED MANY GALAXY POSITIONS IN THE CATALOGUE OF SOUTHERN PECULIAR GALAXIES

Last edited by PeterM; 29-10-2011 at 07:17 AM. Reason: Corrected sn magnitude
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Old 28-10-2011, 09:56 PM
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Interesting ? NGC908 is a fair way out there then, That is a dam nice Image Greg ! Its always great to see what is so far out in quality detail ! Top Job !
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Old 28-10-2011, 10:14 PM
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What a beautiful galaxy photo Greg.

I love the colours.

Ross.
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Old 28-10-2011, 10:18 PM
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A 16803 chip... I suspect... had more than enough real estate for that FOV

That said.... very tidy effort ! Nice one.
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Old 28-10-2011, 10:51 PM
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Quote:
Originally Posted by RickS View Post
A pretty little thing, Greg!
Thanks Rick.

Quote:
Originally Posted by PeterM View Post
Indeed a lovely image Greg. You are going off the beaten track for some excellent results.
NGC908 has had 2 recorded Supernova 1994ai Williams & Martin (Perth Automated Supernova Search) @mag17 & SN2006ce @mag17.5 Monard ( South Africa).
It's about 65 MLY years distant.

Here is a nice little group worthy of the GregBradley treatment
NGC92 & 3 other galaxies AKA ROBERTS QUARTET RA (2000) 00:21:31 DEC -48:37:29 MAG12.9. NAMED AFTER ROBERT FREEDMAN WHO CORRECTED MANY GALAXY POSITIONS IN THE CATALOGUE OF SOUTHERN PECULIAR GALAXIES
Thanks for the tips. I'll check them out.

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Originally Posted by astronobob View Post
Interesting ? NGC908 is a fair way out there then, That is a dam nice Image Greg ! Its always great to see what is so far out in quality detail ! Top Job !
Thanks for that. Its good to have new imaging targets.

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Originally Posted by Ross G View Post
What a beautiful galaxy photo Greg.

I love the colours.

Ross.
Cheers Ross.


Quote:
Originally Posted by Peter Ward View Post
A 16803 chip... I suspect... had more than enough real estate for that FOV

That said.... very tidy effort ! Nice one.
Yes its cropped as its a relatively small galaxy and in the full wide field view it looks a bit small.

Greg.
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Old 29-10-2011, 01:16 AM
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Quote:
Originally Posted by PeterM View Post
NGC908 has had 2 recorded Supernova 1994ai Williams & Martin (Perth Automated Supernova Search) @mag17 & SN2006ce @mag17.5 Monard ( South Africa).
It's about 65 MLY years distant.
Hi Pete,
Two supernovae in under 20 years sounds like a good rate!
It is worth keeping an eye on this galaxy for SNe....

A few "back of the envelope calculations" show that NGC 908 could be a good candidate for multiple observable supernovae in the future:

(1) If its estimated luminosity in the Hyperleda database is correct (Absolute blue magnitude of -21.4) then NGC 908 is noticeably more luminous than the Milky Way.
(2) This galaxy is likely to be very comparable to the first-ranked spiral galaxies in the Virgo Cluster of Galaxies, such as M61 and M100, for instance, the total star formation rate of NGC 908 (derived from its far-infrared luminosity) is similar to that of one of these large and luminous spirals in the Virgo Cluster.
(3) This is a physically large galaxy, bigger than the Milky Way Galaxy, and it has Very Strong spiral arm structure.
(4) Its U-B color index shows that there is plenty of ultraviolet light, coming no doubt from a large population of OB stars.

These four facts indicate that NGC 908 has a significant rate of current star formation, and therefore a high rate of core-collapse supernovae. It is a nearby and physically large Sc spiral galaxy with strong spiral structure, very much like some of the other galaxies that have had several observed SNe.

I am wondering about the faintness of the observed NGC 908 supernovae, as per your post.....were they underluminous type II events? Or was there heavy extinction within this galaxy that made them fainter than they should have been?

best regards, Robert
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Old 29-10-2011, 06:37 AM
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Good pick up Rob. 2006ce should have read a bright 12.4 have corrected.

Greg that is a huge field you have and there would do justice to some fine off the beaten track southern galaxy groups that often get overlooked. Roberts Quartet being a good example. I can post some more if you like. In fact with about 1500 galaxies in my supernova list I am often really surprised how lovely some of these far Southern galaxies are but not many have been tackled by amateurs in the way you presented NGC908.

From New Scientist and so obvious in your image "The spiral arm on the left side of galaxy NGC 908 has been bent upwards by a near-collision with a passing galaxy (Image: H Boffin/VLT/ESO)" http://www.newscientist.com/articlei...eighbours.html

Last edited by PeterM; 29-10-2011 at 07:16 AM.
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Old 29-10-2011, 09:08 AM
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Nice image Greg. You have a lot of detail there and the colour is good too.

Cheers

Steve
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  #11  
Old 29-10-2011, 09:44 AM
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Quote:
Originally Posted by PeterM View Post
Good pick up Rob. 2006ce should have read a bright 12.4 have corrected.

Greg that is a huge field you have and there would do justice to some fine off the beaten track southern galaxy groups that often get overlooked. Roberts Quartet being a good example. I can post some more if you like. In fact with about 1500 galaxies in my supernova list I am often really surprised how lovely some of these far Southern galaxies are but not many have been tackled by amateurs in the way you presented NGC908.

From New Scientist and so obvious in your image "The spiral arm on the left side of galaxy NGC 908 has been bent upwards by a near-collision with a passing galaxy (Image: H Boffin/VLT/ESO)" http://www.newscientist.com/articlei...eighbours.html
Quote:
Originally Posted by madbadgalaxyman View Post
Hi Pete,
Two supernovae in under 20 years sounds like a good rate!
It is worth keeping an eye on this galaxy for SNe....

A few "back of the envelope calculations" show that NGC 908 could be a good candidate for multiple observable supernovae in the future:

(1) If its estimated luminosity in the Hyperleda database is correct (Absolute blue magnitude of -21.4) then NGC 908 is noticeably more luminous than the Milky Way.
(2) This galaxy is likely to be very comparable to the first-ranked spiral galaxies in the Virgo Cluster of Galaxies, such as M61 and M100, for instance, the total star formation rate of NGC 908 (derived from its far-infrared luminosity) is similar to that of one of these large and luminous spirals in the Virgo Cluster.
(3) This is a physically large galaxy, bigger than the Milky Way Galaxy, and it has Very Strong spiral arm structure.
(4) Its U-B color index shows that there is plenty of ultraviolet light, coming no doubt from a large population of OB stars.

These four facts indicate that NGC 908 has a significant rate of current star formation, and therefore a high rate of core-collapse supernovae. It is a nearby and physically large Sc spiral galaxy with strong spiral structure, very much like some of the other galaxies that have had several observed SNe.

I am wondering about the faintness of the observed NGC 908 supernovae, as per your post.....were they underluminous type II events? Or was there heavy extinction within this galaxy that made them fainter than they should have been?

best regards, Robert
Thanks for the info on the galaxy. I find it interesting.

Quote:
Originally Posted by Stevec35 View Post
Nice image Greg. You have a lot of detail there and the colour is good too.

Cheers

Steve
Thanks Steve. I am looking for new and unusual targets. I guess you get to that point eventually if you image enough objects.
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  #12  
Old 29-10-2011, 09:46 AM
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Quote:
Originally Posted by PeterM View Post
Good pick up Rob. 2006ce should have read a bright 12.4 have corrected.

Greg that is a huge field you have and there would do justice to some fine off the beaten track southern galaxy groups that often get overlooked. Roberts Quartet being a good example. I can post some more if you like. In fact with about 1500 galaxies in my supernova list I am often really surprised how lovely some of these far Southern galaxies are but not many have been tackled by amateurs in the way you presented NGC908.

From New Scientist and so obvious in your image "The spiral arm on the left side of galaxy NGC 908 has been bent upwards by a near-collision with a passing galaxy (Image: H Boffin/VLT/ESO)" http://www.newscientist.com/articlei...eighbours.html

I would love your supernova list to check out targets that could be imaged. I see unusual northern galaxies being imaged all the time by Adam Block. I am sure we have just as many as I was under the impression that galaxies are evenly distributed throughout the Universe.

What is Roberts Quartet?

Greg.
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Old 29-10-2011, 10:10 AM
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Hi Greg,
Roberts Quartet is the one including NGC92 I noted above. I will go through my list in the next few days and post some of the more interesting targets for you.
PeterM.
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Old 29-10-2011, 11:47 AM
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Nice work Greg.
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Old 29-10-2011, 02:25 PM
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Greg, you've got a nice angle on that galaxy - not that you had much choice! I like its strong spiral arm structure too.

Chris
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Old 29-10-2011, 10:59 PM
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Nice work Greg.
Cheers Louie.

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Greg, you've got a nice angle on that galaxy - not that you had much choice! I like its strong spiral arm structure too.

Chris
Thanks Chris. The image has been rotated to present the galaxy in its most flattering angle. From the camera it was in a vertical orientation.

Quote:
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Hi Greg,
Roberts Quartet is the one including NGC92 I noted above. I will go through my list in the next few days and post some of the more interesting targets for you.
PeterM.
Thanks Peter. I look forward to your list.

Greg.
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Old 30-10-2011, 10:21 AM
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Two peculiar galaxies associated with NGC908

The NGC899/IC 223 pair

I would like to mention a pair of very interesting galaxies that are near in the sky to NGC 908.
NGC 899 and IC 223 are pair of galaxies separated from each other by 4.9 arcminutes, and both of them have some strange aspects to their structures.

This (probably) physical pair of unusual galaxies is just over 30 arcminutes from NGC 908, and the redshifts (recession velocities) of all three galaxies are so similar that they are very likely to belong to the same physical grouping of objects.
NGC 899 is the larger of the two galaxies, at some two arcminutes across and Blue magnitude 13, though it should be said that catalog magnitudes and dimensions of peculiar objects are more likely to be inaccurate.

Here is a Blue + Red wavelengths composite of two DSS images of this pair, taken from the Aladin virtual telescope:

Click image for larger version

Name:	N0899_J+R__equals blue +red__SERC DSS1 plus ESO Survey with MAMA___also IC223.jpg
Views:	8
Size:	164.9 KB
ID:	103038

The upper of these two galaxies is IC 223 and the lower is NGC 899. On this image, they both look a little odd, and there is a trace of interesting knotty material outside the main optical body of NGC 899.

If we now look at the version of DSS at http://server1.wikisky.org (which is very contrasty), the image of NGC 899 begins to look very interesting indeed:

Click image for larger version

Name:	N0899_DSS from wikisky.jpg
Views:	5
Size:	60.5 KB
ID:	103037

In this image, there is probably a definite detection of a good number of small knots outside the main body of NGC 899.
One could call this an irregular galaxy, but really it does not resemble any normal irregular galaxy!


Now when I used the GalexView virtual telescope (on the internet) to bring up the GALEX satellite (Far Ultraviolet plus Near Ultraviolet) image of these two interesting galaxies, I got one hell of a surprise......
IC 223 (the smaller of the two galaxies) seems to have a strange FUV emitting region (FUV displays as blue) well outside of its main body.
And NGC 899 looks extremely strange in ultraviolet light; it has far-ultraviolet emitting knots arrayed in a very odd pattern that looks like it might conceivably be unusual arms that surround a disky main body. These knots are, on the balance of probabilities, likely to be giant knots of very luminous OB stars, but other explanations cannot be excluded.

Here is the GALEX ultraviolet (color coded composite of FUV + NUV) image of these two galaxies:

Click image for larger version

Name:	I0223 (top)__N0899(bottm)__FUV+NUV.jpg
Views:	11
Size:	196.7 KB
ID:	103036

It could be a hard job to pick up the knotty material surrounding NGC 899 in amateur images....it is faint in optical images!
(the Far-ultraviolet regime is extremely sensitive to even modest amounts of blue/ultraviolet emitting material!)
___________________________________ __

The unusual Outer Arm of NGC 908

The "upward bending" (or downward bending!) of a spiral arm in NGC 908, as mentioned in PeterM's interesting link, is an interesting phenomenon in some spiral galaxies.
It is more obvious in blue-sensitive images of this galaxy, as the dust distribution in this arm is also peculiar:

Click image for larger version

Name:	N0908_B band__OSUBSGS.jpg
Views:	3
Size:	160.0 KB
ID:	103039

(this is a B-band (blue) image of NGC 908 taken from a survey known as OSUBSGS)

A similar phenomenon is seen in a good number of spiral galaxies, but it is easy to miss it if you aren't alert to the possibility that an arm could bend away from the principal plane of a galaxy.
( Apparently, even our own Milky Way Galaxy has an outer spiral arm that is not exactly in the same plane as the rest of our Galaxy.)
_______________________________

P.S.

As mentioned in my previous post in this thread, NGC 908 is likely to be very comparable to the giant Virgo Cluster Spirals M61 and M100. One more piece of evidence for this assertion is that the measured maximum Circular Rotational Velocity of NGC 908 is similar to that of M61 and M100.....which is a strong indication that these three galaxies are of very comparable mass.
[[ R.B. Tully's "Nearby Galaxies Catalog" gives rotational velocities (which is a mass estimator) for nearly the entire population of spiral galaxies within 3000 km/s ]]
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Old 30-10-2011, 11:15 AM
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Nice work on capturing this little beaut Greg!
Love your background, super smooth and the colours you've obtained are nice and rich while not being over saturated.

Have wanted to get this one down myself but nothing but cloud here for the last two weeks.

A little soft but as you've commented, seeing and conditions weren't great.

Thanks for sharing.

Rich
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Old 30-10-2011, 11:23 AM
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[QUOTE=madbadgalaxyman;779899]The NGC899/IC 223 pair


Thanks for that research. I will add that to the list of things to image.
I appreciate your input.

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Nice work on capturing this little beaut Greg!
Love your background, super smooth and the colours you've obtained are nice and rich while not being over saturated.

Have wanted to get this one down myself but nothing but cloud here for the last two weeks.

A little soft but as you've commented, seeing and conditions weren't great.

Thanks for sharing.

Rich
Thanks Rich.

Its a cropped image and a small galaxy and quite faint. As far as softness goes I suspect I could do a bit better if my rig were at my dark site on a good night but apart from that I think this is the limit of this scope and what it can do or close to it. Perhaps an AO unit may improve it a bit.

Greg.
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Old 30-10-2011, 12:22 PM
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Greg,

I have sent some of the images of the nearby peculiar galaxy pair to a few of my professional contacts.

It will be interesting to see whether or not I have found something really unusual!

Robert
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