M 7 (NGC 6475) Open Cluster in Scorpius
Located at: RA 17 hours 53 minutes 54 seconds, Dec -34 degrees 47 minutes 00 seconds
Size: 80' (50'-75')* Magnitude: 3.3 Class: I 3 r
North is up
West to the right
8" f5 Newtonian reflector
Miranda Laborec 35mm camera, manually guided, hypered Kodak Technical Pan 2415 film, 37 F outside temp
No filter, 40 minutes, 08/26/1990
D-19, 6.0 minutes @ 69F, 35mm negative scanned with Polaroid SprintScan 4000 (4000 dpi)
Scan is a crop from 35mm negative, scan processed in Photoshop CS5.1
Mt Pinos, CA
|Notes:*||This cropped field with the 8" is approximately 1.3 x 2.5 degrees,
and contains several other objects. In addition to M 7 (centered), my
software lists a Globular Cluster (NGC 6453), parts of a several other
Open Clusters (NGC 6444, NGC 6455 and Cr 355), and a couple of small
Planetary Nebulae. My software (Megastar v5.0.13) does not identify the
Dark Nebula within the borders of M 7, but the online Barnard Atlas
(Plate 24) indicates it is B 287.
This is a recent (06/26/2012) scan, as I had hooked up my scanner to capture the last few Messier film negatives for this project.
Most of the film scans from the 8" f5 Newtonian reflector were centered on the object of interest, and were generally scanned to file as a 2000 x 2000 pixel crop of the 35mm negative. This image is a scan of about 80% of the 35mm negative (3500 x 5400 pixels).
Reduced in Photoshop to 1024 pixels, and saved under "Save for Web & Devices".
*According to "Star Clusters", by Brent Archinal and Steven Hynes; "50' diameter, 75' diameter with outliers."
From the NGC / IC Project:Contemporary Visual Observation(s) for NGC 6475
NGC 6475 = M7 = E394-SC9 = Cr 354 17 53 51 -34 47.6 V = 3.3; Size 80 18" (7/21/04): at 92x at least 300 stars are visible in the cluster, though very difficult to count due to the very large size (overfills the 42' field). The more concentrated part of the cluster spans perhaps 30' and includes a dozen stars of mag 7.5 or brighter in the main body. This cluster is much larger and brighter (very prominent naked-eye), but it is much more scattered than M6 and so is less impressive. There are several bright, distinctive strings in the cluster including a N-S string of ~8 stars on the east side of the central region. An equilateral triangle of mag 6, 7 and 8 stars with sides of 3' is on the NW side of the core of the cluster. A clump of 5 stars is near the center including two mag 6 and 7 stars. On the south side of the center of the cluster is an 11' string of 5 mag 5.6 to 7.8 stars oriented SW-NE with the bright mag 5.6 star on the SW end a distinctive yellow color. 13.1": very bright, very large, impressive but scattered, overfills 52' field. Open cluster H18 lies 45' SE and globular cluster N6453 40' WNW of center. Prominent naked-eye cluster in dark sky. Includes several blue-white and yellowish stars. 8": overfills 40' field, not many faint stars, scattered. - by Steve Gottlieb
This description of B 287 from the on-line Edward Emerson Barnard "A Photographic Atlas of Selected Regions of The Milky Way":