Difficult globular clusters.

[Xilman]

Globular clusters are popular subjects for deep sky imagers, and rightly so. However, some are very popular because they are easy. Omega Centauri and M13 are perhaps the outstanding examples. Anyone with a smart phone or better can image those.

I have started imaging less popular ones because, in the words of JFK sixty years ago, we do these things not because they are easy but because they are hard.  This one is Segue 3, which is quite likely the smallest and faintest globular cluster in the entire galaxy. It has 32 known members and a total brightness of only a few hundred times that of the Sun. The brightest member is just 17th magnitude and the next half dozen or so are 19-20. This image goes almost to 21.0 and shows about half of the cluster members.  A similar image, which goes slightly fainter, can be found at https://aladin.u-strasbg.fr/AladinLite/ where you should set the co-ordinates to 21:21:31.0 +19:07:02 and zoom in to a FOV of 5-10 arc minutes.

 

Technical details: 3150 second unfiltered exposure in 53 subs. 0.4m aperture Dilworth scope and a SX 814 CCD camera.

Other imagers who are up to a challenge are urged to post their own efforts. If you wish for some easier targets on which to cut your teeth, you could do worse than start with the Palomar clusters. Beware: Segue 3, Balbinot 1 and AM 4 are hard.

Go for it!

Edited November 2, 2022 by Xilman
Fix minor punctuation errors

[Xilman]

Here is another one, which is slightly difficult for an entirely different reason: it isn't in our galaxy at all.

This is Bol 20 in the Andromeda galaxy and at that distance looks essentially stellar. Bol 20 is dead centre in the image. The two faint stars next to it are, indeed, stars of magnitude 17.0 and 17.4.  Bol 20 is magnitude 14.9 and so should be accessible to visual observers with a 14" or larger telescope and a decently dark sky.

Messier 110 is nearby and within a somewhat wider field of view than is encompassed by my relatively long focal length telescope.

Edited November 2, 2022 by Xilman

[Paul M]

Here is a crop of an image of M110 I did last year. It shows Bol 20 quite nicely

Red ticks mark the spot.

I know there are a few others in there. I'll have to identify them sometime.

Edited November 2, 2022 by Paul M

[Xilman]

Very nice image! You're perilously close to resolving individual stars in M110. Some of the orange granulation seems (to me, anyway) rather denser there than the noise at the edges of the image and much denser than the orange-red stars out there.

M31 has hundreds of GCs, so happy hunting. I have a catalogue of many, probably most, of them. Please ask if you would like a copy.

At least a dozen are visual objects for moderately large Dobsonians --- 30cm and up, say.

Edited November 2, 2022 by Xilman
s/cope/copy/ Grrr, spill-chuckers!

[tomato]

Here is an image of M87 when I was attempting to capture the plasma jet emanating from the central black hole. I think I picked up some of the huge globular clusters that surround the galaxy.

[Paul M]

3 hours ago, Xilman said:

Very nice image! You're perilously close to resolving individual stars in M110. Some of the orange granulation seems (to me, anyway) rather denser there than the noise at the edges of the image and much denser than the orange-red stars out there.

M31 has hundreds of GCs, so happy hunting. I have a catalogue of many, probably most, of them. Please ask if you would like a copy.

Thanks! I took the original image in September last year and was quite pleased with it. Some nice gentlemen here offered to have a go at processing my data to improve the S/N ratio. 

Here is the original thread :https://stargazerslounge.com/topic/382786-m110/#comment-4137241

I'd be pleased to receive a copy of that M31 GC catalogue. I enjoy tracking down obscure objects!

2 hours ago, tomato said:

Here is an image of M87 when I was attempting to capture the plasma jet emanating from the central black hole. I think I picked up some of the huge globular clusters that surround the galaxy.

If they are those specks just above the background then they are positively swarming. I'll have to go and look at my own rendition of M87's jet now, see if I caught any.

 

[Xilman]

29 minutes ago, Paul M said:

If they are those specks just above the background then they are positively swarming. I'll have to go and look at my own rendition of M87's jet now, see if I caught any.

 

Most of them are.  M87 has well over 10K known GCs and those are just the ones bright enough to be seen at that distance and not obscured by the galaxy proper.

One ex-M87 GC is notorious for being ejected from the entire Virgo cluster. It is blue-shifted, despite being far enough away for the Hubble flow to be significant. I'll dig out my image and post it here.

 

Please message me with your email address and I will send the catalogue.

[josefk]

Fascinating images and commentary here @Xilman and @Paul M and @tomato. I'm not an imager but to get insight into captures like these of such distant and/or small objects is brilliant. Thanks. 

[tomato]

I do get a buzz from attempting to image objects on the the limit of my equipment’s capabilities. The images will of course, never match those from million (or even billion) dollar professional equipment, but just the fact that some photons from objects and events which are on unimaginable time and distance scales can be captured on kit residing in my back garden never fails to amaze me.

[josefk]

51 minutes ago, tomato said:

I do get a buzz from attempting to image objects on the the limit of my equipment’s capabilities. The images will of course, never match those from million (or even billion) dollar professional equipment, but just the fact that some photons from objects and events which are on unimaginable time and distance scales can be captured on kit residing in my back garden never fails to amaze me.

100% absolutely 100%

[Xilman]

46 minutes ago, josefk said:

100% absolutely 100%

Same here.

On my bucket list are some quasars at a redshift of >3.  AFAIK my limit is approaching z=6 but those might take several nights of subs.

[Xilman]

18 hours ago, Xilman said:

One ex-M87 GC is notorious for being ejected from the entire Virgo cluster. It is blue-shifted, despite being far enough away for the Hubble flow to be significant. I'll dig out my image and post it here.

Here it is. Doesn't look very impressive, just a small dot. Nonetheless it is a globular cluster which shines at magnitude 20.61. Messier 13 at that distance, 16.4 megaparsec, would be mag 22.5 which shows how intrinsically luminous is HVGC-1.

The GC is approaching us at 1026 km/s and is leaving the Virgo cluster of galaxies at 2200km/s --- it is no longer gravitationally bound and is a true "intergalactic wanderer".

4110 second exposure in 137 subs, unfiltered on a 0.4m Dilworth.

 

[Paul M]

@XilmanI've been playing with the catalogue you sent Paul, lots to look at and I see a future mosaic project on M31 to track down many more of the GCs.

I've already found a few of them on my uncropped image of M110 referenced above. As is often the case my goto software is ASTAP. One feature I haven't used so far is the tool for adding a marker at a given RA/DEC on a plate solved image.

It is only suitable for single item identification but I've found about 5 so far by cutting the coordinates for suitably placed GCs from the catalogue and pasting them in the input field in ASTAP.

Here we see Bol 035 at mag 17.48

Yeah, looks like star but we know the little secret being hidden in those few pixels !!

 

 

 

 

 

[Xilman]

Beware, it might be a very wide mosaic.  Some of them aren't even in the same constellation.

Based on the easy visibility of mag 17.5, in an image not taken for that specific purpose, you should have no difficulty at all going fainter than mag 20 with your kit.

 

Good luck