Globular Clusters in M31

[Richard N]

Last Thursday I had an enjoyable EAA session. I "spotted" Holmberg III a rather faint galaxy which was nice (just the faintest smudge) but the highlight actually came today. I had imaged the core of M31 with a view to looking at it in more detail to see if I could see any globular clusters. Somehow it seemed cool to see a GC in another galaxy. Anyway, the result was a success. The lower image is mine. JPEG=>FITS=>Aladin (Compared with GALEX). EDIT: my wife thought a globular cluster sounded like a sort of chocolate. Ferrero Rocher anyone?

 

Edited September 15 by Richard N

[CraigT82]

That’s really interesting! Nice work, what was the kit used? 

[Richard N]

Just now, CraigT82 said:

That’s really interesting! Nice work, what was the kit used? 

It’s in my post signature. Let me know if you need anything else. 

[Richard N]

Just noticed the signature isn’t visible on a phone. 
 

Svbony 80ed. Mono planetary camera. ZWO AM3. 

[Xilman]

Excellent!  I encourage people to go beyond the usual boundaries and to try to image individual stars, GCs, open clusters, etc outside our galaxy.

If you, or anyone else, would like catalogs of GCs in nearby galaxies please let me know and I will provide. Hundreds, if not dozens, are within range of typical amateur equipment.  Some are as far away as the Virgo cluster of galaxies.

[Xilman]

Note that GCs in M31 and M33 are so close to us that the larger ones show noticeable disks if the seeing is good enough and the telescope aperture is sufficient. Not resolution, of course, but enough to distinguish them from stars.

Edited September 16 by Xilman
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[PeterC65]

I was observing M33 last week with the Explorer 200 and could see NGC604 quite clearly, which I hadn't realised before was a star clusters within the galaxy. The following day with some post processing I could see several of the star clusters in M33. Amazing to think that these objects that we normally observe in the Milky Way can be seen in other galaxies with just amateur kit. @Xilman I'd be interested in your list of other clusters within galaxies.

 

[Xilman]

Peter: I will send you some files by email if you give me your address. I am paul at leyland dot vispa dot com.

Everyone else: I really must have a rummage to see if I can find a round tuit. When one shows up I will put a number of catalogues on www.astropalma.com

 

[Xilman]

This thread has prompted me to look at the catalogues I possess and correlate them with a table I created which gives limiting magnitude for a range of telescope apertures and exposure times with a cooled astrocamera. It assumes decent but not exceptional skies, such as I have here in La Palma --- Bortle 3/4 and 3 arcsec seeing.

TL;DR: most everyone can reach magnitude 20.0, though anything under a 150mm (6 inch) will probably take several nights to reach that.

 

Here's the table. Values are good to about 0.2 magnitudes..

Aperture (cm)	1 minute	20 minutes	1 hour	3 hours	10 hours
8 15 20 25 30 35 40 45 50	13.3 14.6 15.3 15.7 16.1 16.5 16.8 17.0 17.2	16.5 17.9 18.5 19.0 19.4 19.7 20.0 20.3 20.5	17.1 19.1 19.7 20.2 20.6 20.9 21.2 21.5 21.7	18.9 20.3 20.9 21.4 21.8 22.1 22.4 22.6 22.9	20.2 21.6 22.2 22.7 23.1 23.4 23.7 24.0 24.2

Folk have posted images here and on CN which use well over a hundred hours of data collection. A Seestar 50 can manage mag 20 with ease in that time. My 40cm telescope could almost certainly go down to mag 24. The faintest object I have yet imaged was 22.4 or thereabouts and it took 3 hours or thereabouts. We are not restricted to Local Group galaxies either. A number of globular clusters in M81 exceed 19th magnitude. Some in the Virgo cluster reach mag 20 or 21. All can be imaged with a 150mm telescope and a little effort.

[PeterC65]

I sometimes check what is the faintest star I can see when doing EAA, so 5-10 minutes of total exposure time, and with my 8" Newtonian I can usually see down to magnitude 18 which stacks up with your table @Xilman.