[ngcles]

Hi All,

First destination for the evening was an open cluster/nebula complex in Vela that was mentioned as a target on the Ice in Space Forum by Andrew James. Andrew thought it surprising that this OC/nebula/multiple star didn’t make it into Hartung’s AOST. This is what he wrote in that thread:

“Les I also like this object in the same area as the Pencil;

Cr 197 (08 44.7m -41 deg 17') and Gum 15 / RCW 32 (08h 44.6m -41 deg 17') is an open cluster containing the small bright nebula known as Gum 15 which surrounds the multiple star of I 815. Surprisingly missed in AOST2, it can be found some 2.2 degrees North of the wide pair of 4th magnitude d Velorum / HJ 4133 (08 44.4m -42 deg 39') and 0.8 degrees N of NGC 2671 - our Pencil - which is an open cluster..
This open cluster covers about 17 arc min of sky whose nine stars, whose brightest four stars make up the multiple 1815. At 6.7 total magnitude, its singular blue star, followed by the remaining yellow stars, are classed as “3 3 m n” - the “n” being the bright nebula Gum 15.
South African visual observer Auke Slotegraaf claims to seen the clusters' shape as triangular in 11×80 binoculars, but comments it was "... Not an easy object." I looked for this in 7×50 binoculars and did not really see much. Auke also observed the cluster in his 25cm (10") f/5 Newtonian at 30x.. Describing it as a "typical Collinder cluster", he describes its shape as;

"... reasonably large and the brighter members seem to lie in an uneven, curving V-shape grouping of l l stars, 5 of which are pretty bright. The 'V' points north to a very unequal double star, [I 815]…"

I 815 (08 44.7m -41 deg 17') is the multiple star whose four components are listed as AB (7.3v and 11.5v, 4.4 arcsec 2 deg), AC (7.2v and 13.3v, 8.3 arcsec 130 deg) and AD (7.2v / 11.0v 35 arcsec 225 deg). I 815 appears on Map 397 in Uranometria 2000.0 drawn with the "box" of nebulosity of superimposed Gum 15. The AB and AD pair was first discovered by Innes in 1911, and AD is the widest an most easiest to see. The AB system can be seen with 10.5cm with care and is easier in 20cm - the problem being the magnitude difference. AC is slightly more difficult, and should be visible in 20cm under good seeing and moderately high magnification. Again, the five-odd magnitude difference made it hard combined with the faint 13.3 magnitude. I glimpsed I 815 C once in 30cm in moderately good seeing and made a rough sketch. This later star was discovered by Innes in 1933.
All stars in this system are bluish-white, likely matching the spectral class of B3/5 II of the primary. Little has changed in the positions since discovery, and it is uncertain if these stars are dynamically behaving like multiples or as open clusters, but they certainly must be associated. 1 815 certainly adds to the Cr 197's appearance.

As for Gum 15...

"Gum 15 (08h 44.7m -41 deg 17') is the faint emission nebulosity centred on the primary 7.3 magnitude star of the double I 815, of which, can be imaged some 10 arcmin around it. Telescopically in the 30cm it appears as a faint haze about 1 arcmin across, which is significantly enhanced with averted vision. The proximity of the component stars make it a bit of a challenge to see.
It is possible that 25cm, or even 20cm, might be able to see this nebula, but larger apertures may see a little more nebulosity. Either way, to see Gum 15 you will need dark and fairly transparent skies."


After seeing it for myself, I find myself in respectful disagreement:


RCW 32 Gum 15 Bright Nebula
RA: 08h 44m 36.0s Dec: -41° 17' 00"
Mag: --- Size: 20.0' Class: E Source: Sky Cat

Cr 197 Open Cluster
RA: 08h 44m 40.0s Dec: -41° 16' 36"
Mag: 6.7 Size: 17.0' Class: III 3 m n
# of Stars: 40 Source: Lynga *

I 815
RA: 08h 44m 40.3s Dec: -41° 16' 38"
Components: Mags: 7.2 / 11.0
Spect: # Obs: ---
Obs Dates: --- / --- Sep: 35.0 / --- p.a.: 225 / ---

Well, this was at the top of my list last night after this discussion and I can't find myself in agreement AJ about it being overlooked for AOST. Sorry!

I observed it with the 18" with the 16mm T2 at x139 35' TF, 20mm T2 at x111 with 44' TF and 26mm T5 x85 58' TF, with and without UHC, OIII and H-Beta filters and the best view was with the 20mm T2 unfiltered.

The cluster is a poor and scattered one with no central condensation apparent and is completely resolved. There are slightly more stars N of the central star than south of it. It is dominated nr centre by the multiple star Innes 815. All three of the faint companions in Innes 815 are easily seen at x111. The cluster contains 20-odd stars scattered over about 15 arc-mins diameter and is not detached from its surrounding fields -- the borders of the cluster are not defined at all and the field seems equally rich as the cluster. Large variation in brightness between members between mag 7 to 13.

The visible portions of Gum 15 is considerably less than the DSS shows and are pretty faint. I thought the best view was without the filter. The nebula is classified as "E" but it does not seem to have much/any emission component as to me it seemed dimmed to the UHC and completely disappeared with the O III and H-Beta. Only a maybe 2-3 arc-min diameter very LSB haze surrounding but mainly to the N of Innes 816 with no defined border.

I also took another look at the (nearby) OC NGC 2671 at x138 and in the 18" it is a nice object. Seems about 7 arc-mins in diameter as a well detached splash of 3 dozen-odd faint stars mainly in the 13th to 14th mag range pretty homogenous in brightness. Within the cluster a large triangular-shaped group on the N side stands out with points of that triangle at centre, PA 30 and PA 330, about 3-4 arc-mins a side. Quite nice. Seems completely resolved and no residual haziness is evident. The NGC indicates a diameter of 4 arc-mins -- I think this is a bit of an under-estimate -- more like 7 arc-mins and the magnitude should be more like about 9 rather than 11.6v.

So, with that out of the way it was high time for some galaxies in Hydra, but after only 20mins observing it was clear that it was going to be a very, very dewy night. Not only dewy, but also cool if not tending cold – 11 deg C (at 10pm and dropping further later) might be okay in winter, but February? Dew became a real problem a few rimes – I can’t remember a more damp night for years and at lest three times, I had to pause and “cuddle” the secondary mirror cell to drive off the mist of condensation forming and keeping the eyepieces free from condensation was equally challenging. But the rewards were great — for Bargo it was terrific!

During the course of the next few hours of course I looked at things other than tiny faint galaxies. Most of the highlights of the late summer sky were looked at, and Saturn was really beautiful after 12mn when it was near culmination. But here are the Hydra observations.


x 185 x27' TF

IC 2327 Galaxy *
RA: 08h 21m 28.1s Dec: +03° 10' 10"
Mag: 14.2 (P) S.B.: --- B-V: ---
Size: 1.3'x0.4' Class: Sa? P.A.: 168
Inclination: 6 R.V.: +2463 Source: RC3 *

IC 503 Galaxy *
RA: 08h 22m 10.9s Dec: +03° 16' 08"
Mag: 13.9 (P) S.B.: --- B-V: ---
Size: 1.1'x0.9' Class: SBa P.A.: 65
Inclination: 1 R.V.: +4131 Source: RC3 *

These two are both very small and faint eg that are almost identical except in PA. Both seem to be about 30 x 10" elong oval with 2327 being in PA 0 and -503 in PA 90. Both rise weakly in brightness to the centre without apparent core. They are about 10' apart. -2327 makes an eq Tri about 11' a side with two mag 9 *s -- to the N and NW. The NW star has a mag 11 companion.



x 185 x27' TF

IC 504 Galaxy *
RA: 08h 22m 41.2s Dec: +04° 15' 46"
Mag: 14.0 (P) S.B.: --- B-V: ---
Size: 1.2'x0.8' Class: S0 P.A.: 140
Inclination: --- R.V.: --- Source: RC3 *

IC 505 Galaxy *
RA: 08h 23m 21.7s Dec: +04° 22' 21"
Mag: 14.7 S.B.: --- B-V: ---
Size: 1.1'x0.5' Class: S P.A.: 143
Inclination: --- R.V.: --- Source: PGC *


IC 506 Galaxy *
RA: 08h 23m 30.7s Dec: +04° 17' 58"
Mag: 14.7 S.B.: --- B-V: ---
Size: 0.6'x0.6' Class: E/S0 P.A.: ---
Inclination: --- R.V.: --- Source: PGC*

These three galaxies are found in the same quite starry field (for Hydra) and all are small and faint or worse. The brightest is 504 which is found at the end of a short curved string of 5 mags 11-12 *s that is roughly E-W. Small, maybe 30" diameter, faint with LBS rising slightly and broadly to centre without core or nucleus. 505 is 10' NE.

505 is smaller and slightly fainter than 504, 20" diameter if that, round and has a slight central brightening.

506 is to the S of -505 by 6 and is almost *ar, very small < 15" diameter tiny scrap of mist that wouldn't be visible, hardly to be seen except that it can be found by reference to the others from the DSS.

x185 27’ TF

IC 513 Galaxy *
RA: 08h 33m 05.2s Dec: -12° 21' 17"
Mag: 14.5 S.B.: --- B-V: ---
Size: 1.0'x0.6' Class: SB(rs)0^? P.A.: 40
Inclination: --- R.V.: --- Source: RC3 *

This is a very small and pretty faint eg in a field with quite a few faint stars. Two mag 11 *s point directly at it from the NE a couple of ac-mins away and to the NW a couple of arc mins are 4 faint stars. Tiny 30" dia halo, round or possibly slightly elong in PA 30 (in the direction of the two mag 11 *s) with a weak central brightening and no apparent core/nucleus.



x185 27' TF

NGC 2617 Galaxy *
RA: 08h 35m 38.8s Dec: -04° 05' 16"
Mag: 14.1 S.B.: --- B-V: ---
Size: 1.1'x0.8' Class: S0/a pec: P.A.: 92
Inclination: --- R.V.: --- Source: RC3 *

MCG -1-22-26 PGC 24141 Galaxy *
RA: 08h 35m 48.4s Dec: -04° 05' 33"
Mag: 14.1 S.B.: --- B-V: --- Size: 0.9'x0.7'
Class: S0 P.A.: 38
Inclination: --- R.V.: --- Source: PGC *

Through the ep this is a small round eg which isn't too hard to see but pretty faint growing weakly to centre it is only 30" diameter. There are two faint *s superimposed -- just N and just S on the edges of the halo at mag 14. PGC 24141 is E by only 2'.

MCG -1-22-25 is a fraction smaller than the NGC eg and somewhat fainter, a 20-0" dia patch of gossamer with no central brightening that is only convincingly visible with the 9mm.



x185 27' TF

NGC 2615 Galaxy *
RA: 08h 34m 33.5s Dec: -02° 32' 49"
Mag: 13.3 (P) S.B.: --- B-V: ---
Size: 1.9'x1.0' Class: SB(rs)b
P.A.: 40 Inclination: 3 R.V.: --- Source: RC3 *

This is a pretty easy to see eg found to the N of a couple of mag 7 stars by 12'. It appears slightly elong in about PA 30 as an oval shaped maybe 1.25' x 1' lowish SB hazy spot growing broadly and mod azonally to the centre where there is a very faint spot. Revise : there may be a pretty large, weakly brighter and weakly defined core zone that is about 30" diameter within the halo containing the faint spot at centre.


Pt 2 to follow ...