The Roslund star clusters are a collection of 7 clusters in a 600 square degree large area in Vulpecula, Sagitta and Cygnus. They were discovered and spectroscopically examined on photographic plates with a limiting magnitude of 12m5. Because of the low limiting magnitude these clusters should be observable with 4 to 6 inch telescopes. Two (Ro 5 and Ro 6) are even objects for binoculars.
I observed all 7 clusters and made sketches of 5.
I wrote an article about this project which can be found in the German deep sky journal Interstellarum No. 24.
right ascension: 19h45m declination: +17°31' diameter: 3.0' # of stars: 15 Trumpler classification: 41p-
Roslunds description:
The stars form a main sequence beginning with B9 V stars of the 10th magnitude and reaching spectral type A7 at the plate limit
My observation:
5m4, 100x, relative large, about 20 stars, in S more loose and brighter stars, in NE fainter stars and more concentrated. Stands out fairly well.
right ascension: 19h45m declination: +23°55' diameter: 15.0' # of stars: 20 Trumpler classification: 42p-
Roslunds description:
The brightest star (HD 186745-6 7th magnitude) is of type B8 Ia, followed by fainter stars of OB+ and OB down to OB- at the limit of the plate.
My observation:
5m4, 74x, nearly not dividable from the surrounding star field, 3 brighter stars in an right-angled triangle, the easternmost appears yellow. Westward is a small group with about 10 stars with different magnitudes.
right ascension: 19h58m declination: +20°28' diameter: 5.0' # of stars: 20 Trumpler classification: 41p-
Roslunds description:
The brightest star (10th magnitude) is of type B7 II-III, followed by middle and late B main sequence stars.
My observation:
5m4, 100x, fainter stars, the brightest are arranged in a parable shape. The vertex is to south, at the vertex I can detect a condensation. Inside the parable are some scattered stars. Weakly concentrated
right ascension: 20h05m declination: +29°12' diameter: 6.0' # of stars: 30 Trumpler classification: 23mn
Photo by Michael Breite
Roslunds description:
A cluster of OB stars of the 11-12th magnitude. Possibly connected with the two nebulae IC 4954-55
My observation:
5m6, 100x, does not stand out at all, fainter stars distributed in small groups. The reflection nebula IC 4954/55 is involved. Southern part is very faint, elongated NNW-SSE, around 6 stars with 2 doubles. The northern part is even fainter, appears as a faint halo around two stars.
right ascension: 20h10m declination: +33°46' diameter: 50.0' # of stars: 15 Trumpler classification: 42pn
Roslunds description:
The brightest stars (8th magnitude) are of type B9 V, followed by early A main sequence stars.
My observation:
5m7, 39x, very large, many bright stars, the brightest are situated in WSW, only few faint stars, very loose, no apparent concentration towards the middle,
diameter about 1,3°, at least 120 stars
right ascension: 20h28m declination: +39°22' diameter: 50.0' # of stars: 30 Trumpler classification: 43mn
Roslunds description:
The stars form a main sequence beginning with Stars of type AO V of the 8th magnitude and reaching type FO at the plate limit. A K giant of the 7th magnitude, HD 195194, may be a member of the cluster.
My observation:
5m7, 50x, loose and large cluster, bright stars. Divided in western part with the brightest stars and the eastern part with fainter stars. In the middle is space lacking stars.
right ascension: 20h52m declination: +37°55' diameter: 35.0' # of stars: ? Trumpler classification: 42p
Roslunds description:
A somewhat doubtful cluster. The brightest stars (9th magnitude are two stars of type B9 II-III and one K giant. A few fainter late B and early A stars of class III are present.
My observation:
5m6, 74x, in comparison to the other Roslunds not that doubtful as described by Roslund, stands out fairly well, elongated
