September Challenge Object (NB) - NGC6726

[iceman (Mike)]

Hi all.

We'd love you to take part in the September Observing and Imaging Challenge. Please post your reports, sketches and deep-space images of NGC6726 in this thread. Discussions about the images can also be in this thread.

Please ensure the images obey the posting guidelines when you attach them.

While it would be nice if the report, sketch or image were taken in the month of September, it's not essential so feel free to post older reports and images if you're unable to take some new ones.

We look forward to seeing your contributions!

[dhumpie]

Have seen this one but have not sketched it yet. Pretty hard object with small apertures...but doable with a UHC filter in place. I think I see some of the nebulosity surrounding the stars but they are not well defined. But easier to see than the nebulosity surrounding the Pleiades.

Darren

[ving (David)]

well i had a go at this one... after chasing bugs, starfish and ducks it was good to leave the animals alone

right in the middle of the dob hole it was!!! GRRR!

still here we go.
in my 8" with 15mmSV and skyglow filter what is saw was 2 stars, one brighter than the other surrounded in a small amount of nebulosity. just down (down?) from there was another small patch of nebulosity... it was all surrounded by er... nothingness.
its not what we see in pics but i did see something

the near by glob is quite large and dim. i could barely resolve stars in it.
kinda this shape...

[CosMos (Rich)]

Copied this from thread further down. Better placed here.

"A tour through this region is a lesson in stellar evolution, where the young progeny of interstellar clouds mingle with the older generation stars of their neighbourhood.

Those of you who have access to a dark sky have an advantage here. Much of the emission and reflection nebulosity and even the dark nebulae, so beautifully delineated in a black velvety sky, are lost forever to city observers with medium apertures.

The Corona Australis molecular cloud that pervades this region is one of the nearest clouds of its type at an average distance of 130 parsecs (Marraco and Rydgren 1981), around 420 light years, though this figure is still uncertain. Intense study in this region by ROSAT and many other contributors give an approximate mass for this cloud of 3000 to 10000 solar masses. The densest part of the cloud lies near R CrA where upwards of 45 magnitudes of extinction is inferred.

NGC 6726 and NGC 6727 are a pair of faint, round reflection nebulae in contact, forming a haze filled "figure 8". The south-western portion is lit by HD 176386, a magnitude 7.2 A-type star which lies 440 (± 110) light years away and shines with the light of 19.9 (± 9.8) Suns. The northeastern glow contains the erratic variable star TY CorA. The spectral type is B9Vand the light fluctuates from magnitude 8.8 to a faint magnitude 12.5 at minimum. TY CorA is an eclipsing triple system, the primary of 1.6 solar masses and an age of 16 million years. The secondary is expected to be a G or K star (Walter et al 1987). The third stars mass is uncertain, Casey et al (1995) giving it 2.4 solar masses whilst studies by Corporon, Lagrange and Beust (1996) give 1.2 to 1.4. solar masses.

Only 4.7 arc minutes to the south-east lies NGC 6729, a delicate, comet-like wisp, complete with "tail" which encloses the faint variable star T CorA, varying between magnitude 11.6 and 14.3. The position of "nucleus" is taken by another erratic variable, R CorA, the star ranging in brightness from magnitude 10.0 to 14.3. R CorA is a young star in formation, still accreting material onto its disk.

The nebula NGC 6729 itself varies in brightness as the stars within change their energy output and changes in the shape of the nebula have also been observed. Some of these changes may be due to a band of obscuring dust eclipsing the nebula itself or perhaps shadow effects, first seen by J. Schmidt in 1866.

Around 9.2 arc minutes to the west of R CorA lies the variable star S CorA, ranging in brightness from magnitude 10.8 to 12.5.

Only 6.4 arc minutes to the south of S CorA lies a delightful surprise, a pair of white "cat’s eyes" shining at magnitudes 6.6 and 6.8. These B8-type stars, catalogued as BrsO 14, are separated by 12.7 arc seconds, far enough apart to resolve easily though close enough to enhance their jewel-like appearance. This double system is also enveloped by a large and faint expanse of glowing gas, IC 4812, a good target for CCD camera operators.

Having a look back at my observing notes, observations with a 13" telescope from Kumeu in 1991, using a power of 50x, showed all these objects within the same wide telescopic field. The nebulae were difficult but the globular cluster NGC 6723, just over the border in Sagittarius, was an included bonus. This bright and beautiful stellar city was easily resolved. Moving on up to a power of 130x improved the look of the nebulae remarkably, especially "cometary" NGC 6729."