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NGC 6723 and Friends (NGCs 6726, 6727, 6729, IC 4812, etc.)

Technical card

Imaging telescope or lens: VIXEN R200SS

Imaging camera: ATIK 383L+ mono

Mount: SkyWatcher AZ-EQ6

Guiding telescope or lens: Orion 50mm guidescope

Guiding camera: Orion Starshoot Autoguider

Software: PHD Guiding 2SkyTools3ATIK Dawn Image processingGoodLook

Filter: Baader Planetarium LRGB Filter Set

Accessory: Vixen Coma Corrector 3

Resolution: 3115x2503

Dates: Aug. 9, 2015Aug. 11, 2015

Baader Planetarium Blue: 6x600" -10C bin 1x1
Baader Planetarium Green: 6x600" -10C bin 1x1
Baader Planetarium Luminance: 9x600" -10C bin 1x1
Baader Planetarium Red: 6x600" -10C bin 1x1

Integration: 4.5 hours

Darks: ~10

Flats: ~8

Avg. Moon age: 25.11 days

Avg. Moon phase: 21.15%

Bortle Dark-Sky Scale: 4.00

Temperature: 6.50 job: 731070

RA center: 285.243 degrees

DEC center: -36.961 degrees

Orientation: -2.129 degrees

Field radius: 0.779 degrees

Locations: Home observatory, Glenorie, NSW, Australia


NGC 6723 in Sagittarius is the globular cluster shown in the lower left part of the image. It is spans 87 light years across at a distance of approx. 28,500 light years. The bright (blue) reflection nebulae just over the boundary in Corona Australis (the Southern Crown) are much closer to us at 420 light years. The brightest one with the two cores has two NGC numbers 6726 and 6727. To the upper left of that is IC 4812 close to the double star that is easily recognised because of its twin diffraction spikes. Slightly above NGC 6726/6727 is the small white/yellow triangular nebula NGC 6729 that surrounds variable star R Coronae Australis. Close by that is the hook shaped Herbig Haro Object which is being thrown off by a newly born star. The new star's rotation probably determines the shape of this object.

The reflection nebula are set against the backgound of the Milky Way but the myriad of stars there is obscured over large parts of the image by clouds of gas and dust. The denser parts hide almost all of the background stars while the thinner parts show up as brownish/grey clouds. At the distance of the dust clouds and nebulae the image spans 9 light years. This means that all of the “close by” objects in the image are packed into a region only twice the size of the distance from our Sun to its nearest star.

I'm finding this field difficult to process. But I think that the latest revision is an improvement.




Sky plot

Sky plot


NGC 6723 and Friends (NGCs 6726, 6727, 6729, IC 4812, etc.), DavidLJ