LDN 52, NGC 6520, B86 - Part of the Large Sagittarius Star Cloud

Large Sagittarius Star Cloud

The photograph shows the central part of the Large Sagittarius Star Cloud, which is the densest star cloud of the entire Milky Way. Although it lies in the direction of the center of the galaxy, it is in fact located in the nearby spiral arm called the Sagittarius arm and not in the galactic hub. The western edge of the cloud is limited and obscured by interstellar dust clouds. There is perhaps ten times more dark matter in the Milky Way then is contained in stars or glowing nebular material. The center of the galaxy is obscured by as much as 30 magnitudes of absorbing material!

LDN 52 is the designation of the large-scale dark lanes in the lower part of the image. This is a so-called dark nebula, interstellar matter which absorbs the light of the stars sitauted behind it. The designation "LDN" stands for Lynds Catalog of Dark Nebulae, which was published in 1962, and is based on the Palomar Observatory Sky Atlas.

Barnard 86 is the black spot located in the upper part of the image which spans 4.5' x 3'. It is charmingly placed next to the small open cluster NGC 6520, together they make a nice contrast. B86 is just a little smaller than the cluster and is essentially a dust cloud absorbing the starlight from behind it. NGC 6520 has an apparent size of 5 arcminutes and contains 25 stars from magnitudes 9 down to 12.

Near the lower bottom of the imaged field two globular star clusters can be seen close together: NGC 6528 at left and NGC 6522 at right. They look almost like stars, albeit a bit more fuzzy. NGC 6528 has a brightness of 9.5 magnitudes and a size of 3.7 arcminutes, while NGC 6522, the larger and brighter of the two, has magnitude magnitude 8.6 and an apparent diameter of 5.6 arcminutes. The bright red star near the lower left corner is Nash, Gamma Sgr, the "spout" star of the "teapot" which can be interpreted into the constellation Sagittarius.

The Large Sagittarius Star Cloud is bright to the naked eye and increases in brightness the further south the observer is located.

Great Sagittarius Starcloud - telelens photograph.

Exposure Data

Instrument: TMB 4.1" f/6.2 APO
F/stop: 6.2
Exposure: 25 minutes
Film: Kodak Farbwelt 400
Exposure start: 00:40 MESZ
Date: July 8, 2002
Location: Ebenwaldhöhe, Lower Austria
Conditions: Visual limiting magnitude 5.0 mag, seeing 2, temperature 12°C, no wind, low to moderate humidity
Autoguider: Meade Pictor 216 XT, max. error: 1
Enhancement: Adobe Photoshop 7.0, SGBNR 1.0.4
Notes: Low altitude of photographed field. The negative color film turned out to be unsuited for emission nebulae due to H-alpha insensitivity, but it works well for starry fields.

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