NGC 6664 rating MEDIUM
open cluster in Scutum
RA 18h 36.7m Dec -08d 13.5' (2000)
When it comes to open star clusters, the small Milky Way constellation of Scutum is best known for M11. But in fact, there are at least a dozen open clusters in Scutum. One of these, NGC 6664, is an easy find because it sits just 20' east of 4th-magnitude Alpha Scuti.
NGC 6664 is a sparse cluster embedded in a rich part of the Milky Way, and covers an area about one quarter that of the full Moon. It looks like a partially resolved cloud in a 2.4-inch refractor. In a 6-inch you can see about 35 stars in a 25' area, with the brighter ones mostly on the north side.
A 10-inch scope at medium powers will show 60 or more stars, all fainter than 10th magnitude. Overall, the cluster has no central condensation and is highly-elongated north to south.
A study by Halton Arp of reddening of cluster members reveals a cluster distance of 1,450 parsecs, or about 450 light-years. The cluster contains a Cepheid variable star as a member: EV Scuti varies from 9.9 to 10.3 over a 3.09-day period.
NGC 6629 rating HARD
planetary nebula in Sagittarius
RA 18h 25.7m Dec -23d 12.3' (2000)
This challenging little planetary lies in Sagittarius roughly 2 degrees north, and just a bit west, of 3rd-magnitude Lambda Sgr, which marks the top of the Sagittarius teapot. Closer in, you'll find it 7' south of 8th-magnitude SAO 186800. This is a difficult planetary for small scopes, even through an OIII filter, but it can be detected with averted vision.
In larger scopes, such as an 8-inch at 110x, NGC 6629 looks like a very faint round diffuse ball with no discernable edges. In a 10-inch scope at 100x, it looks like a 10th-magnitude star. At 250x its about 15" in diameter, fading abruptly at the edge.
The magnitude of the central star is 12.9