Ic4720/21

[Shiraz]

The largest of the two main galaxies is IC4721, a barred spiral about 80-100 million light years away. The elliptical close to IC4721 is IC4721A (a background galaxy). IC4720 is the smaller spiral separated by about 8.8 arc minutes from IC4721 and apparently at about the same distance.

The “feather” extending from the side of IC4721 is not part of the galaxy, but is a background side-on spiral galaxy that is about 180 million light years further out and can be seen through IC4721. Such fortuitous alignments, including this pair, have been used to estimate the density of galactic material by way of attenuation of light from the background galaxy. There are quite a few other fuzzy blobs, including one at lower left in a line with two main galaxies and one almost at the top of the frame – these two have similar colour to the main galaxies, so could just possibly be related. The thin side-on galaxy in the lower right corner is also intriguing.

The seeing was fairly good at 2.5 arc sec averaged over three fairly short periods, but it really requires a lot more good data to do this target justice. However, this was all that the clouds have allowed, even after including some slightly dodgy data that upset the star shapes. There was also significant sky brightness and galactic extinction, so the final balance was by eye to try to get reasonable stars as well as plausible galaxy colours.

It is now getting a bit late for this RA and, unless the weather patterns change, it is unlikely that there will be another opportunity to image this region for now - will be worth a revisit next winter to do a proper job.
Thanks for looking. Regards Ray

Refs: NED database and associated links and
http://arxiv.org/pdf/1211.6723.pdf

GSO200f4 with RCC1
SX H694
NEQ6

2.25 hours L, ~2 hours RGB total, all 200sec subs at 1x1
heavy crop and reduced by 0.75 (native scale 1.17arcsec/pixel)

[Lee]

Well done Ray - the star colours have come out really nice - and some nice detail in the galactic arms....

[Larryp]

Very nice, Ray

[LewisM]

Spectacular.

I counted 11 GX in total - anyone know EXACTLY how many in that FOV?

[Shiraz]

Thanks Lee. data could have been a lot better, but I was pleased to get a result.


thanks Laurie


Good call Lewis - i think I can see the 11 you found - bit difficult to find more in jpeg compressed data, but a lot of the dim red stuff is not particularly star-like in the full scale original.

Regards Ray

[LewisM]

13 now :)

[Shiraz]

:thumbsup:

[nebulosity.]

:thumbsup::thumbsup::D

[SkyViking]

Stunning image! Those galaxies are beautiful and it's a nice bonus with the overlapped one. Great detail and colour too, the processing looks very natural. Thanks for the view :)

[tilbrook@rbe.ne]

Oustanding Ray!:thumbsup:

You say it needs more data to do it justice.
Amazing with the data you have.

Cheers,

Justin.

[strongmanmike]

Lovely galaxy pair that Ray with some good detail, the little overlapping galaxy is a bonus :thumbsup: Very nice work

Mike

[Shiraz]

thanks Jo


thanks very much Rolf - appreciated. just found a reference to the overlapping background galaxy - it is 2MFGC 14479 and it is about 265 million light years away (about the same as IC4721A)


Thanks Justin - you know what the weather has been like lately down this way - I was glad to get as much data as I did.


Thanks very much Mike. the overlapping galaxies are neat.

regards Ray

[marco]

Very nice field and excellent "natural" processing Ray, I really like it :thumbsup:

Clear skies
Marco

[Paul Haese]

Like the processing Ray, star colours and galaxies look great. Well done.

[multiweb]

Wow! Top notch Ray! Straight to the cool wall. :thumbsup::thumbsup::thumbsup:

[Shiraz]

thanks Marco - I am trying to keep processing to a minimum, so appreciate your comment.


Thanks very much Paul


Thanks Marc. For me the cool bit is that this is what the background galaxies looked like before the dinosaurs made an appearance on earth..

regards Ray

[gregbradley]

That's a wonderful image Ray. Haven't seen that one before. Do you think that is a companion galaxy below and to the left of the main galaxy?

It seems it may creating some distortions in the main galaxies shape. A longer exposure may pick up some tidal streams perhaps. You can see some disturbances in the right hand side of the galaxy.

Hard to believe its only 4.25 hours to get a result like that. I also think that is excellent processing.

Greg.

[PRejto]

Great image Ray!! Beautifully processed for such limited data!

I'm counting down to the arrival of my Trius! (Sadly not until November when I will bring it back from the States...)

Peter

[White Rabbit]

Yeah lovely star colours, they have come out well. Looks really good.

Cheers.

[RickS]

Very nice, Ray! That set up is working well. Have you tried to measure any of your results and compare them with the original spreadsheet calcs?

[Shiraz]

thanks very much Greg. As I understand it, the two main galaxies are about 90 million light years away and they are probably interacting. There is another quite separate pair of background galaxies that are about 265 million light years away and they are possibly also interacting with each other - they are the beautiful elliptical "ball" appearing to just touch the big galaxy and the "feather" edge on spiral shining through it. Quite a spectacular grouping really.
I guess it is possible that there is a tidal stream between the main two galaxies - there might even be a hint of an extension of the bigger one in that direction. I did not get anywhere near enough data to show a complete stream, but it will certainly be worth looking for next time around.


Thanks Peter. It was frustrating to get enough data to show something good but not quite enough for top quality - it was worth posting the results though - this area is so interesting.
Looking forward to seeing how you go with the new cam - but November... never heard of patient amateur astronomer before :lol:. My approach is to procrastinate on a decision for ages and then get upset if I cannot get what I eventually decide on within a couple of days.

thanks Sandy


Thanks Rick.
I have not actually done a formal comparo. Did some really rough back of the envelope sensitivity tests early on and found that it all seemed to match up well enough with the design specs, so decided to just use it as is. The resolution also looks like it is close to spec and my initial guess of 2 arcsec seeing was pretty much on the money - the average good seeing has been about 2.5 FWHM with occasional bursts below 2 and as bad as 6 arcsec at times. The design spec for the final scope of 250f4 will be about right when I get it, but the current 200f4 is also not too bad a match to seeing.
I will probably publish the spreadsheet in the near future, since it has turned out to be a very valuable tool so far and could possibly be of use to others. It was informative to be able to study performance aspects of the design in quite some depth before it was built - showed where money and effort would give the best return.

Regards Ray

[Shiraz]

Hi again Greg. pushed and inverted the original luminance data to see if there was any sign of tidal streams between the two foreground galaxies - nothing I can see at this exposure length. These cameras certainly do have stuff all noise - this is with no pre-processing, just median stacking. Regards ray

[Stevec35]

Top shot Ray! Great star colour and very natural processing.

Cheers

Steve

[pvelez]

Ray

here is a screenshot of Aladin for part of your field indicating objects recorded in Simbad - you have captured all of the galaxies that I can see on this shot - including the tiny one behind the main galaxy at about 7 o'clock.

Great job

Pete

[Shiraz]

Thanks Steve - appreciate the comment


Thanks very much for taking the trouble to do that Pete - nice to have some of the image features identified.
I have not used Aladin - looks like an essential tool, so thanks for the tip.

regards Ray

[pvelez]

Ray

here is the link - its a great tool. When you have it running, you can switch on Simbad which sets up an overlay of links to the Simbad database. Click on the star,galaxy or other object and it will open the relevant page in Simbad. Very easy

http://aladin.u-strasbg.fr

Pete

[Shiraz]

thanks Pete - almost too easy, must be a catch... :thumbsup:

[Ross G]

A beautiful galaxy photo Ray.

I love the colours and composition.

Ross.

[Shiraz]

thanks very much Ross. regards Ray