Observing Report w/48-inch from April

[Steve Gottlieb]

On April 16 through the 19th, Howard Banich and I made another pilgrimage to the shrine of Jimi's observatory in Fort Davis, Texas. I posted a 3-part observing report on Adventures in Deep Space, or go directly to Part 1, Part 2 and Part 3.

Here's one exotic object we viewed -- an extragalactic globular cluster in Sextans A.
Sextans B is a nearby dwarf galaxy discovered by Albert Wilson at Palomar in 1952-54 (though some sources cite Fritz Zwicky as the discoverer). It is generally considered to lie just outside the local group in a small group including Sextans A, Antlia Dwarf and NGC 3109. Our main target was not the galaxy itself, but a globular cluster discovered in 2007 in the eastern side of the galaxy!

I've observed this galaxy a few times in my 18-inch. Here's the last observation: Easily visible at 175x as a large, low surface brightness, oval patch, extended 3:2 NW-SE, ~3.0'x1.9'. The glow is nearly parallel to two mag 13 stars off the NE side and extends roughly the separation of these stars (3'). This dwarf galaxy has only a broad, weak concentration with a slightly brighter core and an ill-defined edge to the halo as it fades at the periphery. Still, the surface brightness is slightly irregular with a hint of mottling. Located 8' NE of mag 7.7 HD 86610.

In the 48-inch, Sextans B appeared as a large, fairly low surface brightness oval glow, extending 4:3 WNW-ESE, ~2.6'x1.9'. It exhibits a broad weak concentration to a slightly brighter middle, but there is no distinct core or zones. The surface brightness is irregular and slightly clumpy. A mag 14.5 star is at the north edge of the galaxy and a mag 15 star is off the southeast edge of the galaxy.

This young (2 ± 1 billion years) massive globular cluster (SDSS J100004.63+052007.5) was discovered in 2007 in Sextans B using the HST WFPC2 and verified at the Special Astrophysical Observatory in Russia. This roughly 18th mag, it appeared as an extremely faint "star" and was visible only intermittently, though repeatedly confirmed. The stellar glob is located ~1.2' ENE of the center of Sextans B. Definitely a target for large scopes.

Sextans.B.jpg

[Uwe Glahn]

Hi Steve,

very nice observations and objects in your parts. Sounds like lots of fun - I wish I could be there.

Thanks for the tip for the GC in Sextans B For Sextans A and B I could add respectively 2 observations.

Sextans A
4", 30x, NELM 6m5+
difficult with very low magnification because of two faint 12mag stars; with higher power (30x) very faint 3' glow south of an 11,5mag star; difficult to hold glow with averted vision
20", NELM 6m5+
With high EP very faint glow; NW of a faint star group; 4' large, round; SE spot only suspected; very low surface brightness but I could hod glow steadily with averted vision

Sextans B
4", 44x, NELM 6m5+
even with very low power a round glow is visible; best view with 44x; still faint but I could hold glow steadily; round with diffuse edges
20", NELM 6m5+
even in the searching eyepiece brighter glow in a star empty region 8' NE of the 7,7mag bright HD 86610; round structureless 3' large glow

Also funny that you observes UGC 5938/5942. Funny because I also visited this very nice pair at the April new moon period (sketch with 27"). And thanks for the UGC 8584 tip. I will give it a go next months.