More Herschel Clusters

by Tom Campbell


July 1, 2003

ObserverTom Campbell
LocationIola, Kansas (Long: 95=B024'W Lat: 37=B055'N)
EquipmentDiscovery DHQ 8" dobsonian
Eyepieces1.25" Pl=F6ssls - 25mm (49x), 15mm (81x), 10mm (122x), 6mm (203x), 4mm (305x)
Time11:00pm - 12:00am CDT (04:00-05:00 UT)
TransparencyClear (8/10)
SeeingVery Stable (9/10)
WeatherTemperatures in the 80s. There was no breeze.

Observing Summary
When I looked at my Clear Sky Clock this afternoon, I couldn't believe how good the seeing was supposed to be tonight. Shortly before sunset, some clouds could be seen here and there on the horizon, and the sky was a pale blue, indicating perhaps some upper-level haze. Still, I took out my telescope and set up.

I was pleasantly surprised at how steady the stars were through the eyepiece. I defocus bright stars as part of my collimation process, which usually shows wildly swirling and flaring diffraction rings. But after an even shorter cooldown period than usual, the diffraction rings were pretty steady, with very little flaring visible. I decided to set up my telescope in the brightest part of the yard, because it offered me my only view of the southern sky. I hoped to view some more Herschel clusters in that area.

NGC 6645SagittariusOpen Cluster11:05pm CDT
CR 383RA: 18h 32m 36sDec: -16=B0 53'Mag: 8.5

This open cluster was somewhat faint and spread out. The best view was at 122x, where it was framed nicely in the field of view. About 2-3 dozen stars were visible in the cluster, all of which were pretty faint. Two of the brightest stars in the cluster formed a compact triangle with a third, fainter member off near one edge. The cluster consisted mainly of small clumps of stars, with a few loose arcs of stars spilling out the sides.

NGC 6642SagittariusGlobular Cluster11:10pm CDT
RA: 18h 31m 54sDec: -23=B0 29'Mag: 8.9

This globular was fairly faint and small. The best view was at 81x. With direct vision, the cluster almost disappeared, with a stellar core popping in and out of view. Averted vision revealed the fuzzy mass of surrounding stars, although no individual stars could be resolved.

NGC 6638SagittariusGlobular Cluster11:15pm CDT
RA: 18h 30m 56sDec: -25=B0 30'Mag: 9.2

This globular cluster was fairly large and bright. At 203x, the cluser appeared round. Using averted vision, the core had a slightly mottled appearance, but no individual stars could be seen.

NGC 6664ScutumOpen Cluster11:35pm CDT
CR 385RA: 18h 36m 42sDec: -08=B0 13'Mag: 7.8

This cluster was found right off of the much brighter Alpha Scuti. It was loose and large. At 81x, The entire cluster could still be seen. The cluster mainly consisted of long, loose strings of stars, forming a J shape overall. The base of the J was thicker and contained the majority of the visible stars. In all, about two dozen stars were seen. There was a little bit of nebulosity throughout, indicating perhaps several more stars that were just beyond detection with my telescope.

NGC 6882VulpeculaOpen Cluster12:00am CDT
RA: 20h 11m 42sDec: +26=B0 33'Mag: 8.1

This open cluster was large, but sparse. At one edge was what appeared to be a foreground star, much brighter than the cluster members. The cluster itself formed a wide ring, or donut, with very few stars inside.

NGC 6885VulpeculaOpen Cluster12:00am CDT
CR 417RA: 20h 12m 00sDec: +26=B0 29'Mag: 8.1

This cluster was at one edge of NGC 6882, forming part of the aforementioned donut. Its stars were a little fainter and more compact than that of the larger cluster. The best view was at 81x.

I didn't finish off my list of Herschels in the above constellations, but at least I made some progress. The summer viewing sessions are all too short, especially with work the next morning.