This Summer nebula brings to mind 1960's school days - and first views with a friend's 4inch 'scope. I took a lot of photos. Yet this 2010 pencil sketch seems more natural - why? The bright stars have been tweaked with software to suggest their dazzling presence. Specs: 10in. F5. H-beta filter, at an urban site.
Saturday, 20 January 2018
Planetary nebulae are elusive targets - and can be more so if sited amid bright stars. This one adorns star cluster M46 (NGC2438). Often a narrow-field e.p. helps reduce competing glare. This is a pencil sketch but the stars have been enhanced to show their true sparkle: its a beautiful cluster, but we see just a small part here. The nebula is a chance alignment and the 'central' star is unrelated to it.
Sunday, 5 November 2017
Flares fascinate. How and why do these huge high-temperature events erupt? Close study of the polarity of sunspots suggests they occur along the boundary between spots of opposite sign. At least this GOES M4.2 did in AR12673 two months ago. The sketch (lhs) shows the spot group in WL and H-alpha (polarity line in BLUE). The polarity map from the (c)SDO satellite shows the polarity a few hours later.
Friday, 15 September 2017
Sunday, 6 August 2017
This sketch covers a bright field 2 deg. N of LMC centre. The fov is 3 full moons wide and 4 high. It's a big field! The two filaments alpha-alpha and beta-beta are, apparently, anonymous. They are very blue in H-beta. It's presumed they are distorted galactic blue-knots or arms of mainly OB stars. The named features are listed l.h.s. Why did the filaments take this strange shape? They are visible in small binoculars. The 'Dragon's Head' is the only thing with a common (and appropriate) name. The whole looks like an Oriental dragon!
Sunday, 18 June 2017
The writer has always enjoyed viewing double stars, particularly if they are ‘tight’ ones: that is, close pairs that are hard to separate. Although my ‘scopes are not dedicated to the task, ‘tricks’ like using aperture masks and simple orthoscopic eyepieces will often succeed, though the most important factor is steady seeing, that usually occurs later at night.
A favourite example is the ‘double-double’ Nu Scorpii, aka “Jabbah” (Arabic for the Scorpion’s forehead) close to bright star Beta Sco, refer to star maps (P82, Astron 2017). A ‘double-double’ is a quaternary system with two pairs of stars gravitationally bound in a four-star system. As Agnes Clerke wrote (1905): it is “perhaps the most beautiful quadruple group in the heavens.”
Saturday, 7 January 2017
A first 'shot' at this most complex of all nebulae: it showed wonderful detail despite 8 day Moon. The Lucke-Hodge Catalogue numbers are used for two of its clusters _ and the NGC has three numbers for the major nebulae components. When a darker night offers, I hope to develop the fainter detail of the vast extensions. The bright star in LH100 is 30 Dor. The 'little' cluster TM5 is 'anonymous': I guess not catalogued. Who is TM? The brighter bits drawn here are about 800ly across. Fainter outliers extend the whole to almost 2000ly diameter. Hubble views 30Dor and environs! - http://cloudsofmagellan.net.au/photos/hst-r136.jpg