"Mariposa" - from the Cocoon

Mark Wagner

Michelle Stone and Paul Plett hosted a wonderful star party for a large number of friends at their "Plettstone" home in Mariposa County, near Yosemite National Park. A few newer faces were becoming fixtures in the group, and combined with the old friends the feeling was reminiscent of old days in the southwest lot at Fremont Peak, at the height of TAC's early exuberant days. Thanks to Michelle and Paul for such a great time.

I observed on Friday and Saturday nights, finishing around 2:45 a.m. each night. Friday was shorts, sandals and tank top all night. Saturday cooled down a bit, requiring jeans, shoes and a light polartec shirt by late in the evening. Sunup came too soon each morning, but the comraderie helped make the fatigue disappear. I enjoyed the outdoor shower on Saturday, a perfect way to cool down during the heat.

I think the sky was brighter than some of the other times I'd observed there, but the transparency, especially on Saturday night, was excellent.

Without doubt, for me the observing highlight of the trip was an outstanding detailed view of IC 5146 / Sh2-125, the Cocoon Nebula.

Here are my observations - double stars, Herschel 400 (NGCXXXX), Herschel 400-II (NXXXX), Arp catalog, and Sharpless HII/Bright Nebulae (Sh2-XXX). The entire list can be found at:

http://www.resource-intl.com/Deep.Sky.Aug.Sep.08.html

I had a great time... here is what I saw....

Beta Cep Double 13.3 3.2/7.9 21 28 42 70 34
I began the night on Beta Cephei, a nice double with 13.3’ separation, an easy split even at les than 100x. The primary was a nice blue/white and the companion a distinct red/orange.

Sh2-136 Cep BN 5.0' 21 16 05 68 15 11 Two and one half degrees south-southwest sits the small bright nebula Sh2-136. Don’t let the description “bright nebula” fool you, this is a difficult object. I suspected it as a dim glow surrounding SAO 4461:645, and the DSS image appears to confirm the observation. My note says “With the NPB filter it appears round and centered on a star. Better without the filter and seems to extend to northwest. Averted vision required, nebula disappears with direct vision.”

N7129 Cep OC 8.0' 11.5 21 42 00 66 05 00
I moved 3.13 degrees ESE to the open cluster N7129. It is a very nice nebula surrounding three equally bright stars, and a fourth very dim star embedded in a knot of nebulosity, forming almost a parallelogram. The brightest areas of the nebula are around N and S stars. Check out the DSS image on this one, as it gives an idea of how thoroughly the nebula is involved in the nice small cluster. NGC 7142 Cep OC 4.3' 9.3 21 45 12 65 46 23
Only 33 arcminutes to the south-southeast is another small open cluster NGC 7142. It is an amorphous group of stars stretched out mostly to southeast and southwest. Particularly notable is a nice open arc of stars extending to the west. This object has many stars of nearly the same magnitude. Overall, this is a really nice open cluster, that stands out well.

Xi Cep Double 7.7 4.4/6.5 22 03 56 64 38
Off to Xi Cephei, a nice double with two distinctly different magnitudes and easy to split at low power (100x). Primary is yellow, companion is gold. The separation is 7.7 arcminutes, with mags of 4.4 and 6.5. Find it by moving in the same direction as before an additional 2.2 degrees. Easy stuff!

N7139 Cep PN 77.0" 13.3P 21 46 08 63 47 41
Move just over 2 degrees west-southwest to find the surprising planetary nebula N7139. It is large and dim. Initially I thought it was a big round galaxy. It has indistinct edges, a brighter southern edge, which gives it somewhat of an annular feeling. There is a dim star involved in SE edge.

Abell 75 Cep PN 56.0" 17.0P 21 26 23 62 53 33
I moved 2.2 degrees again west-southwest to Abell 75, better known as NGC 7076. At 293x it responds best to OIII. It is visible without a filter, but its envelope improves with OIII. It ma be elongated east-west, and with a brighter eastern edge, giving impression of annularity. Two stars involved, central star is brighter than one toward western edge. I had help observing this target by the young eyes of Elisabeth Oppenheimer, who stopped by to ask a few questions. Thanks for the help Elisabeth!

NGC 7160 Cep OC 7.0' 6.1 21 53 48 62 36 00
Three degrees to the east is the open cluster NGC 7160. It contains two bright stars are set in two curved chains each opening to their south east. I found it difficult to determine the extent of this cluster beyond the chains.

S 2780 Cep Double 1.0 6.0/7.0 22 11 42 59 59
A fairly big hop of 3.22 degrees to the west southwest gets you to the double star Struve 2780. It is easier though to come off of Alpha Cephei and use an optical finder to locate this mag 6.0/7.0 pair. It is a tight double at 1 arcsecond! It was an impressive split at 293X! The pair were just about equal brightness, but it was in somewhat soft seeing.

15 Cep Double 11.1 6.7/11.4 22 03 54 59 49
Moving back east almost exactly six degrees gets you to 15 Cephei. This is a wide double at 11.1 arcminute separation, and widely differing magnitudes at 6.7 and 11.4. It is certainly and easy split at low power, and big different in magnitudes is obvious.

B366 Cep DN 10.0' 3 21 40 03 59 34
>From there I hopped to Barnard 366, three degrees east. Some Barnards are interesting, this one was not in that category. It is in an easy location, very near Mu Cephei. It is simply a not very remarkable dark area, although, there is mottling involved.

Struve 690 Cep Double 19.5 4.1/12.3 21 43 30 58 47
Struve 690 is Herschel’s garnet star. I failed to look at it as a double, but it is. It has a wide separation of 19.5 arcminutes, and a very wide difference in magnitude from mag 4.1 to 12.3. What it is remarkable for is its rich color. I think everyone expects this, a carbon star to be deep blood red, but it never appears that way. It is what I would call “infused” with orange/bronze. It is one of the most colorful stars I’ve ever observed.

S 2816 Cep Double 11.7 5.6/7.7 21 39 00 57 29
Make sure to visit the beautiful tripe star Struve 2816, one and a half degrees south. This is a very pretty triple, two dimmer blue stars flanking a yellow/gold mag 5.7 star.

Abell 77 Cep PN 76.0"x 49.0" 16.4P 21 32 10 55 5242
Next I hopped just under 2 degrees south-southwest. I used Mu Cephei then picked out mag 5.7 SAO 33626 as a “yardstick” to get to mag 6.1 SAO 33458, and from there to the field containing Abell 77 (aka PK97+3.1 or Sh2-128). All I could detect was some slight brightening but very indistinct with OIII and averted vision. Over time I felt there were a few areas of mottling or slightly brighter haze. The object had very indistinct edges.

Struve 2840 Cep Double 18.8 5.5/7.3 21h 52.0m 55 48
Just over three degrees east the double star Struve 2840 was visible at mag 5.5. It is an easy hop from mag 3.4 Zeta Cephei to mag 5.5 SAO 33990, then on a line to mag 5.7 13 Cephei and next to the target. This is an easy low power split of an unequal pair of white stars.

Sh2-127 Cyg BN 1.0' 21 28 41.9 54 37 15
Heading back west three and a half degrees you’re in the neighborhood of Sh2-127. This little nebula is at best a very small hazy spot with averted only. Even then, there are many very dim stars involved in the brightest section, about 3 minutes north-northeast of dim star, so confirming that you are seeing nebula and not a tight grouping of dim stars is tricky. I used a VHT filter to help bring out the glow.

NGC 7128 Cyg OC 3.1' 9.7 21 44 00 53 43 00
On to NGC 7128, a nice small open cluster a bit over 2 degrees mostly west. There are about 12 stars in the group with many dimmer ones forming a haze. The southeastern-most star in the cluster is obviously red.

NGC 7086 Cyg OC 9.0' 8.4 21 30 30 51 35 00
Three degrees west-southwest is the open cluster NGC 7086, Large, splashy, it contains many stars of similar magnitude. It is amazing to compare the variety in appearances of open clusters!

M39 Cyg OC 31.0' 4.6 21 32 12 48 27 00
A three degree hop generally south, and a peek in the optical finder, puts you right on M39. And there is no doubt about it. It is large, very coarse, and roughly the 12 brightest stars dominate the field. Again, the variety in opens could not be more apparent!

N7067 Cyg OC 3.0' 9.7 21 24 12 48 01 00
A degree and a half mostly west of M39 lands you on N7067. It is a nice small open cluster with about 5 stars of equal mag being the brightest, about a dozen dimmer ones interspersed , then many very dim stars as a haze in the background. They appear to form a rough triangle with the southern tip defined by one of the brightest stars. Some dim nebulosity appears to be involved, but seemingly missing in center of cluster and could be just dim stars in the background.

Sh2-125 Cyg BN 8.8' 21 53 05 47 16 18
Sitting five degrees east is another Sharpless “bright” nebula. This one is designated Sh2-125, but is better known as the Cocoon Nebula (IC 5146). I’ve had a number of successful observations in the past, but mostly just some mottling in the area, maybe a distinct shape that let me know I was indeed picking out some detail. But this night’s observation was one for the books. I used an H-Beta filter and was treated to an obvious large and mostly circular glow. Two bright stars were involved, the brightest on southwest edge of the object, the other roughly in its center. The north-northwest edge appeared to be a brighter section, and there was some mottling around the central star giving a feeling of annularity. Over time I began to also suspect more extension of the object to the east-northeast. This was hands-down the best view I’ve ever observed of the Cocoon.

N7082 Cyg OC 24.0' 7.2 21 29 24 47 05 00
Hard to believe an open cluster can be a more difficult observation than the Cocoon, but here’s such a case. N7082 is in an easy location to identify, four degrees west (man, I did way too much hopping around this month!), but because it sits in such a rich Milky Way field, it effectively disappears into it. I know I saw it, but don’t ask me to describe it in any more detail!

NGC 7209 Lac OC 24.0' 7.7 22 05 12 46 30 00
Arrgh! Sorry, I definitely need to better arrange these objects! Back (again – way too much hopping) six degrees east is NGC 7209, now in Lacerta. It is a very nice open cluster with many stars of very similar magnitudes, surrounded by four bright stars, three of near equal brightness, forth is brightest. Nice setting, almost like a gem set in a ring.

NGC 7062 Cyg OC 6.0' 8.3 21 23 28 46 23 03
Even with all the back and forth hopping, I did get to know these areas pretty well. A lot of unnecessary work though. Live and learn. Back again, nine degrees west to NGC 7062 in Cygnus. This open cluster features five stars in nearly a pentagram surrounding haze of many much dimmer stars. Of special note is a beautiful, near perfect chain of five stars outside the cluster, in exquisite “steps” from brightest to dimmest, east to west. Worth the big hop!

B156 Cyg DN 8.0' 3 21 33 59 45 35
B155 Cyg DN 13.0' 3 21 32 08 44 58
Probably the easiest location of the night goes to Barnard 156 in Cygnus, located on the 4th magnitude star Rho-Cygni. This is a black area, totally devoid of any other stars. Very nearby is Barnard 155, which is clearly a large dark void in a rich star field. Both these objects showed best in a TeleVue 101 brought by Richard Navarrete.

Sh2-123 Cyg BN 13.0' 21 42 05 44 32 24
An easy star hop from the two Barnards was Sh2-123, which appeared as a large amorphous glow around and involved in star chain running N/S to the W of two bright stars seperated widely. Neb extends in Y to W of star chain. Subtle is an overstatement.

NGC 7044 Cyg OC 5.0' 12.0 21 13 09 42 29 44
Just under two degrees east-southeast is the fun open cluster NGC 7044. It contains very dim stars of all about same magnitude. With some study, it looks like starfish! In the 12mm eyepiece there is a well populated central area, and spokes or arms extending away in perhaps six directions. Separated from the main cluster to the west is a nice arc of star with many dim ones behind them The arc begins to the southwest, extends obviously west, then arcs back to east but not as far back as the main cluster. This is a fun view.

Sh2-113 Cyg BN 15.0' 21 20 30 38 05 29
I finished the trip attempting Sh2-113 in Cygnus. With my 12mm eyepiece I pulled in one small bright knot, and was centering the object when all the stars suddenly dimmed out. A cloud had moved in, and the sky looked like it was going to continue having broken clouds for some time. This target is worth a return trip, the knot was obvious, but, perhaps I was glimpsing a dim galaxy in the field. I’ll have to check again….

Clear skies,

Mark