NGC 6882/6885 Cluster(s) or asterism(s)?

NGC 6882/6885 is a star group in Vulpecula. It may be made up of several groups. WEBDA has nothing on it but a position. It is Trumpler class III2p so little to no concentration, made up of stars covering a wide brightness range and star poor. I find no distance for it or much of anything in fact. It carries two NGC numbers since it was found by William Herschel on two consecutive nights. September 9, 1784 and September 10, 1784. There's nothing of interest at the position of NGC 6882 but there is for NGC 6885. The position for 6882 lies at a bare region within 6885. To me the cluster is made up of several groups as mentioned above and it may be Herschel saw one of these groups as 6882 but got the position wrong. He got several other objects positions wrong that night. As Dr. Corwin says "WH was clearly not up to snuff that night..." I've had too many of those nights so I'll cut William some slack here.

The first Herschel 400 lists both clusters as two separate objects. This confused me to no end it appears from my notes from May 20, 1985. I wrote of NGC 6885 as seen in my 10" f/5 scope: "Large scattered, open cluster of stars of all magnitudes. Mostly west of 20 Vulpecula (that's the bright blue star in my image). Fainter stars seem to be centered about 4' north and more condensed than the very widely scattered brighter stars. This may account for its two numbers in both catalogs. Dim stars center is about that of 6882." My comments for 6882 written at the same time read: "See 6885 as I was unable to distinguish a second cluster anywhere in the area. 6885 is listed as 20' across and this one only 4' north so inside the other. Burnham, the Becvar catalog and Tiron make no mention of this object! Why not pick another Herschel object to replace this one -- say H-14-5 which is the bright arc of the Veil complex?" I'd forgotten all about this until I went to research this object after processing it.

I had to move the cluster low in the field. 20 Vulpeculae was sending horrid ghosts across the frame when placed higher in the field. Why moving it slightly south solved them I never did figure out. There are three rather bright stars just out of the frame to the north. They sent some nasty gradients into the frame as by moving the field south they almost came into frame. Fortunately GradientXTerminator pretty much eliminated the problem.

As mentioned I couldn't find any distance for the cluster. Three of the brighter stars have Hipparcos data in The Sky which put them only about 120 light-years distant. 20 Vulpeculae is 10 times that at 1,140 light-years.

Weather was a problem while imaging this one. I had to sort through several nights of images to find those used here. Only one green image survived the cut as all others were lost to haze and clouds. Fortunately the one had no satellite and I was able to make it do.

Besides the LRGB image I've included an RGB image. It subdues the faint stars giving a more visual impression of the cluster.

14" LX200R @ f/10, L=4x10' RB=2x10' G=1x10', STL-11000XM, Paramount ME

Rick

Rick,

this is certainly a nice starfield, regardless of it's nature.

Stefan


"WA0CKY" schrieb im Newsbeitrag ...


NGC 6882/6885 is a star group in Vulpecula. It may be made up of
several groups. WEBDA has nothing on it but a position. It is Trumpler
class III2p so little to no concentration, made up of stars covering a
wide brightness range and star poor. I find no distance for it or much
of anything in fact. It carries two NGC numbers since it was found by
William Herschel on two consecutive nights. September 9, 1784 and
September 10, 1784. There's nothing of interest at the position of NGC
6882 but there is for NGC 6885. The position for 6882 lies at a bare
region within 6885. To me the cluster is made up of several groups as
mentioned above and it may be Herschel saw one of these groups as 6882
but got the position wrong. He got several other objects positions
wrong that night. As Dr. Corwin says "WH was clearly not up to snuff
that night..." I've had too many of those nights so I'll cut William
some slack here.

The first Herschel 400 lists both clusters as two separate objects.
This confused me to no end it appears from my notes from May 20, 1985.
I wrote of NGC 6885 as seen in my 10" f/5 scope: "Large scattered, open
cluster of stars of all magnitudes. Mostly west of 20 Vulpecula (that's
the bright blue star in my image). Fainter stars seem to be centered
about 4' north and more condensed than the very widely scattered
brighter stars. This may account for its two numbers in both catalogs.
Dim stars center is about that of 6882." My comments for 6882 written
at the same time read: "See 6885 as I was unable to distinguish a second
cluster anywhere in the area. 6885 is listed as 20' across and this one
only 4' north so inside the other. Burnham, the Becvar catalog and
Tiron make no mention of this object! Why not pick another Herschel
object to replace this one -- say H-14-5 which is the bright arc of the
Veil complex?" I'd forgotten all about this until I went to research
this object after processing it.

I had to move the cluster low in the field. 20 Vulpeculae was sending
horrid ghosts across the frame when placed higher in the field. Why
moving it slightly south solved them I never did figure out. There are
three rather bright stars just out of the frame to the north. They sent
some nasty gradients into the frame as by moving the field south they
almost came into frame. Fortunately GradientXTerminator pretty much
eliminated the problem.

As mentioned I couldn't find any distance for the cluster. Three of the
brighter stars have Hipparcos data in The Sky which put them only about
120 light-years distant. 20 Vulpeculae is 10 times that at 1,140
light-years.

Weather was a problem while imaging this one. I had to sort through
several nights of images to find those used here. Only one green image
survived the cut as all others were lost to haze and clouds.
Fortunately the one had no satellite and I was able to make it do.

Besides the LRGB image I've included an RGB image. It subdues the faint
stars giving a more visual impression of the cluster.

14" LX200R @ f/10, L=4x10' RB=2x10' G=1x10', STL-11000XM, Paramount ME

Rick


--
WA0CKY