The best globular clusters

Click on the image for a higher res version

The 6 best globular clusters of the whole sky are here presented. This comparison is obtained with the same telescope and camera, shown at the same image scale. Processing is nearly the same for each image, even if a small individual optimization was necessary.
For me, living in the Northern hemisphere, it is a bit sad to notice that 5 o 6 have negative declination, and that the best 3 never rise on my horizon in Italy.

Omega Centauri is by far the largest of all, and also the brightest, easily visible to the naked eye.
47 Tucanae is a spectacular subject, expecially in the binoculars, where I can see two globulars, one inside the other (due to the high concentration in the middle).
NGC 6752 is similar to M13, but larger and brighter.
M22 is spectacular for the huge carpet of neighboring stars.
M4 is near one of the most spectacular regions of the sky, the Antares nebulae region.

For a comparison of only Omega Cen and M13, look at "Comparison of Omega Centauri and M13".

Here is a table listing the above globulars.
Ordered by magnitude

Mag Size ['] Dist [kly] Const Dec
Om Cen 3.9 36.3 15.8 Cen -47
47 Tuc 4.9 30 16.7 Tuc -72
NGC6752 5.4 20.4 13 Pav -60
M13 5.8 20 22.2 Her 36
M22 6.2 32 10.6 Sgr -24
M4 7.2 18 7.2 Sco -27
Ordered by size

Mag Size ['] Dist [kly] Const Dec
Om Cen 3.9 36.3 15.8 Cen -47
M22 6.2 32 10.6 Sgr -24
47 Tuc 4.9 30 16.7 Tuc -72
NGC6752 5.4 20.4 13 Pav -60
M13 5.8 20 22.2 Her 36
M4 7.2 18 7.2 Sco -27

 
Technical Data
Optics Takahashi FS152 apo refractor
Focal Lenght 1216 mm (direct focus, no flattener)
Focal Ratio f/8
Exposure Time For each image, respectively: 1h30min, 40min, 1h20min, 1h30min, 1h00min, 20min (single exp of 10 min)
CCD Canon EOS 5D with Baader filter
Sensitivity 800 ISO
Location Tivoli Farm (Namibia) at 1350 m height
Date
23 August - 2 September 2011
Mount Fornax 51
Tracking SXV-H5 on a Vixen 80/640 apo refractor
Temperature and humidity T= from 0 to 20 °C, RH= from 20 to 50%
Sky brightness at zenith (with SQM-L) 21.8-22.2 mag/arcsec^2
Notes This image is a collaborative effort of the Namibia 2011 expedition. Processing: Lorenzo Comolli. Images by: Lorenzo Comolli, Luigi Fontana, Giosuè Ghioldi, Emmanuele Sordini.
M13 was imaged by Giosuè Ghioldi with the same telescope and camera from the Northern hemisphere.


HTML Editing and Publishing by Lorenzo Comolli. Email me at comolli@libero.it.
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