November Observation Challenge

[Jeeps (Sam)]

Originally Posted by mental4astro

Though not part of this month's Challenge, Jupiter had a nice surprise for us, with a shadow transit being visible. Its trek across the disc was noticed over the two hour session we had! Nice treat.

I was out last night and had some terrible fog hanging around and couldn't see much but jupitor was shining through and i thought i initially had some dust or something on the lense but a closer look revealed it to be a shadow! I was still able to push up to 200x and although not the clearest, the shadow was as clear as day! The fog became worse so i packed it in but not before i was able to see the shadow dissapear all the way around. What a great find in an otherwise unusable night!

cheers

[Suzy]

I only managed to get ngc121 (next to 47 Tuc) for the first time. I only saw it for no more than 5 seconds before the clouds rolled in. My plan for the night was to try and get all three little globs surrounding Tuc.

Thanks Glen for the list of all those objects. I'm printing them out and keeping them in my observing folder.

[ngcles]

Hi Alex and All,

Excellent choices just want to add a bit more information, draw your attention to two frequently overlooked non-NGC clusters in the same region and then play pick the odd man out.

Okay! Closer to 47 Tucanae than NGC 176 and 152 are Kron 7 and Kron 3, perhaps better known as Lindsay 8 & 11 respectively. They are both not far outside the outskirts of 47 Tucanae to its south and southeast, comparable in distance from 47 Tucanae as NGC 121 is to 47 Tucanae's northeast.

From WEBDA, the position (J2000) for Kron 3 is: RA 0 24 47 Dec -72 47 39 and for Kron 7 is: RA 0 27 46 Dec -72 46 55.

And here is an image of the two, side-by-side from the DSS plate. The image is 10 arc-mins high by 20 arc-mins wide. Kron 7 on the left and Kron 3 to the right.

http://stdatu.stsci.edu/cgi-bin/dss_...e&fov=NONE&v3=

These two are certainly doable in a 25cm 'scope, though Kron 7 is a very tough object. Kron 3 is very similar in size and brightness to NGC 121.

Both these two clusters along with all the ones herementioned (Kron 3&7, NGC's 121, 152, 176) were all considered globular cluster candidates until relatively recent times. However, given the evidence as to Metallicity, RR Lyrae-type variables, the Colour Magnitude Diagrams etc, only NGC 121 could be properly considered as a classical globular because it has ultra-low metals, several RR-Lyrae variables and the CMD indicates an age approaching 11gyrs along with a good horizontal branch.

All the others are populous, intermediate metallicity, aged (about 3-5gyr) open clusters. Just because they aren't G.C's doesn't mean they're not interesting! It's just that they don't fit the classical definition of a GC as having (in basic terms) (1) Ultra-low metalliticy, (2) very low main-sequence turn-off point, (3) strong Red Giant Branch and perhaps most importantly, a (4) distinct Horizontal Branch within their CMD containing RR-Lyrae variable stars.

Both the SMC and LMC are littered with clusters of this sort that look globular and are frequently marked as G.Cs when they're not classical G.C's.

In summary therefore, the two extra clusters are Kron 7 and Kron 3, perhaps better known as Lindsay 8 & 11 respectively. The odd man out is NGC 121 -- a true GC !


Best,

Les D