Target: NGC 6397 in Ara
Camera: QHY 8 OSC
Scope: GSO CF RC200
EFR: f/8
Mount: EQ6 Pro
Exposures: 32min in 5 lights 2x3 1x6 2x10 captured 8/10/2010 between 8:00 and 9:30pm (would have been more but the dog pulled my power cable sometime in the sequence and this is all I got)
Seeing: No moon, no wind, warm night average seeing
Guiding: Orion Starshoot Autoguider using PHD with ED80
Focus: Focus Bahtinov mask
Stacking: DSS no darks and flats
Processing: PS CS3
Globular cluster NGC 6397 (= Lacaille III.11 = Dunlop 366 = Bennett 98), class IX (Class VII, VIII, IX: The cluster stellar density is more homogeneous and less contrasted) in Ara.
Right Ascension 17 : 40.7 (h:m) Declination -53 : 40 (deg:m) Distance 7.2 (kly) Visual Brightness 5.9 (mag) Apparent Dimension 26.0 (arc min)
Discovered by Lacaille in 1751-52.
This conspicuous globular is one of the two nearest to us (the other one is M4); currently it seems that M4 is a bit closer: M4 is at about 6,800 and NGC 6397 at 7,200 light years, but the uncertainty is large enough that the sequence may change..
NGC 6397 is one of the at least 20 globulars of our Milky Way Galaxy which have undergone a core collapse, i.e. its core has contracted to a very dense stellar agglomeration; this is the nearest such globular
In 2004, a team of astronomers[ focused on the cluster to estimate the age of the Milky Way Galaxy. The team consisted of Luca Pasquini, Piercarlo Bonifacio, Sofia Randich, Daniele Galli, and Raffaele G. Gratton. They used the UV-Visual Echelle Spectrograph of the Very Large Telescope to measure, for the first time, the beryllium content of two stars in the cluster. This allowed them to deduce the time elapsed between the rise of the first generation of stars in the entire Galaxy and the first generation of stars in the cluster. They added in the estimated age of the stars in the cluster to arrive at an age for the Galaxy (about 13.6 billion years, which is nearly as old as the universe itself).
In 2006, a study of NGC6397 using the Hubble Space Telescope was published that showed a clear lower limit in the brightness of the cluster's population of faint stars. The authors deduce that this indicates a lower limit in mass for stars to develop a core that is capable of fusion, and obtain a value of approximately 0.083 times the mass of the Sun
Thanks Marc, Ara is more SW while Scutum is more NW for me. Anything NW to NE is the part of the sky most affected by LP in Perth from where I'm located.
