M 6 (NGC 6405) Open Cluster in Scorpius 

Located at: RA 17 hours 40 minutes 17 seconds, Dec -32 degrees 16 minutes 00 seconds

Size: 30' (33') Magnitude: 4.2 Class: II 3 r

North is up

West to the right


 14.5" f5 Newtonian reflector stopped to f6 (12")


Miranda Laborec 35mm camera, manually guided, hypered Kodak Technical Pan 2415 film, 36 F outside temp


No filter, 20 minutes, 06/29/1992


D-19, 7.0 minutes @ 68F, 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 is one of the Messier objects not currently 'visible' from my Thousand Oaks observatory ... In an effort to 'fill in' my Messier images page, I will post what film images I have. 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 14.5" 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.

Reduced in Photoshop to 1600 pixels, and saved under "Save for Web & Devices".

According to "Star Clusters", by Brent Archinal and Steven Hynes, the size of this open cluster is 33 arc minutes.

From the NGC / IC Project:

Contemporary Visual Observation(s) for NGC 6405
NGC 6405 = M6 = Butterfly Cluster = Cr 341
17 40 21 -32 15.3
V = 4.2;  Size 15

18" (7/21/04): at 92x roughly 200 stars are visible in this beautiful naked-eye 
cluster.  There are four bright mag 6-7 stars in the main group which form a 
perfect parallelogram with longer sides of 7' oriented WSW-ENE and shorter sides 
of 4' oriented NW-SE.  A string of stars connects the two stars on the long 
southern side of the parallelogram (the star at the SE vertex is BM Sco) with a 
nice double star embedded in the string.  The NW vertex is part of a bright 
isosceles triangle with two mag 8-9 stars and ~7' further NW of this star is a 
small, nice asterism consisting of a trio and a double.  Also a wedge-shaped 
group of 7 stars extends between this NW vertex (which also has two additional 
fainter companions) and the SW vertex (short side of parallelogram) Another 
distinctive string of stars runs through the center of the parallelogram roughly 
parallel to the two long sides.  A nice mag 9/10 double resides along the long 
northern side of the parallelogram.  An additional mag 7 stars is the SW of the 
parallelogram.  Around the main group there are numerous scattered stars and the 
cluster does not have a distinct border.

13.1": very bright, fairly large.  Includes a curving rows of stars and a close 
group of 7 stars near the center.  The brightest star BM Scorpii is on the E 
side.  Smaller than M7 but richer.  Fairly easy naked-eye cluster.

- by Steve Gottlieb