Pyxis globular & Westerlund 1

[weltevredenkaroo]

Can any of you confirm observations of the Pyxis GC and the massive young cluster Westerlund 1 in Ara? What were the observing conditions, location, and equipment?

[Jim Chandler]

I've observed the Pyxis GC, but not Westerlund 1.

Pyxis GC:
January 2005
Latitude 30N, altitude 450 meters, NELM 7,
Transparency 9/10
Seeing 8/10

25" f/5.0
185x - 631x

Dim g.c., not seen at low power, barely visible with averted vision & higher power. No stars resolved, just repeated fleeting glimpses of a scattering of points, sort of a grains-of-salt-on-black type mottling.

[Uwe Glahn]

Westerlund 1
12", 214x, NELM 7m+ (Hakos/Namibia)
not visible

17", 260x, NELM 7m+ (Hakos/Namibia)
no glow or cluster character at the OC position; around OC some fainter star clouds; at the OC position only a few extremely faint stars

24", 300x, NELM 7m+ (Hakos/Namibia)
very faint; mottling structure at the OC position; some stars are blinking in and out of view but I can not hold them; a little bit NE-SW elongated; faint star group in the direct neighborhood (NE)
1520

Pyxis GC
20", 187x, NELM 7m+, Roque de los Muchachos (Spain)
extremely faint but sure observation; at the N edge three stars visible; directly S a very faint round glow; approx 2' in diameter
1521

[weltevredenkaroo]

Thank you, Uwe, for the Wd1 and Pyx GC info. I'm doing an article for the NMASSA S African newsletter, re adapting professional astronomer field-count methods to verify visual observations. My skies are just over the border from Namibia, so the same quality. Your info is very helpful. =Dana in SA

[weltevredenkaroo]

Addendum to Uwe: Your small triangle of stars edging Pyx are mag 15.1, 15.5, and 16.1. The cluster's brightest RGB is 16.3 and the HB/RC is 19.25. Koposov 2014 (arXiv:1403.3409v2) suggests an associated stellar stream 12° x 15 arcmin, somewhat skin to Pal 5. Pyx is one of half a dozen GCs with a very large core radius (14 PC for Pyx) and sparse 0.65 concentration, which suggest late-stage dissolution as with a number of Pals, E3, and NGC 2298. At 40 KPC out in the halo, this could take awhile. Thanks again, Dana

[Preston Pendergraft]

Not to get off on too much of a tangent, but how safe is observing in some of those remote areas of Africa? I bet the skies are just incredible!

[weltevredenkaroo]

I will send you a PM, Preston.

[Dragan]

I will send you a PM, Preston.

Actually, a public reply would be great! By all means, go off tangent. I'd like to know as well! I'm in the early planning stages of a South African observing trip with Dave Kriege and Bob Rose. Though it would be at a dark site preserve, I'd still like to know a locals opinions on things as I'm sure they would too.

Thanks!

[akarsh]

Dragan, Jim, Uwe et. al -- very interesting object!

Do you folks think I stand a chance trying it with my 18" from central Texas? (30 °N latitude)? At first glance, I thought I might have a chance given that Uwe observed it with a 20" from Spain (is it even visible up there?), but I just noticed that it is from the Spanish territory at 28 °N, not in the mainland!

I might nevertheless give it a foolish shot next time I get a chance. I'm hoping that the skies will clear as promised by forecasters on Monday, but humidity in Texas hill country is going to be in the high 90 percents :-(

Clear Skies
Akarsh

[KidOrion]

A new article on Westerlund 1 is in the ESO's magazine, The Messenger: http://www.eso.org/public/announcements/ann15024/

[akarsh]

Dear all

After some encouragement from Jimi back in May, I shot for the Pyxis globular in my 18" last night. It was on the meridian at the time of observation, and it fortunately passed between some trees that were otherwise obstructing the south horizons. This was at Ft. Griffin State Historic Site in Texas, SQM readings were 21.3 mag at zenith.

The object was much easier than the blue POSS II image suggested. There was a distracting asterism a bit further west of the object, but once one identified the asterism as not being the object, it was clear that there was a small round glow at the exact location. I would say that there are some Palomar globulars (eg: Palomar 3) that I find more difficult than this object despite the declination.

I estimate the size of the glow to be about 40 ~ 50 arcseconds (compared to field stars).

Incidentally, my planetarium reports that Pyxis globular is now technically in Vela, having crossed the border due to precession.

Clear Skies

Regards
Akarsh

[wvreeven]

I managed to observe this globular cluster tonight from the Rio Hurtado valley in Chile using my 20" telescope. At 256x I occasionally saw a faint glow touching and overlapping with a triangle of faint stars. At 545x the glow disappeared but I did see 3 of 4 stars pop up a few times where the glow was. A tough object to observe, even when it's close to zenith.

[ScottH]

Thanks to Akarsh's positive report, I easily found the Pyxis GC in my 16-inch on a recent evening and in my 10-inch at 260x a few days later. The night I looked at it in my 10-inch was what I would consider excellent with 21.65 mpsas at the zenith and excellent seeing all around. But hey, I'll take it!

Scott H.