[Paddy (Patrick)]

It seems a very long time since a cloud free night coincided with an absence of moon. So time to wheel out the 16". Here are the notes from a very good evening in Sagittarius.

Telescope 410mm f4.9 tri-dob reflector
Eyepieces 28mm UWAN, 17,13,9 mm Naglers, Paracorr
Observing guide and maps: Night Sky Observer’s Guide (NSOG)

Seeing 2/5 and transparency 6/7

2040

Clear skies! First observing for too long. The evening starts with the beautiful triangular conjunction of Venus, Mars and Saturn low in the western sky.

NGC 6818 PN in Sagittarius Type 4
Dia 17” Mag 9.3

175X At first glance appears a fairly uniform small blue disc, but careful inspection reveals a brighter edge to the disc on the SW side. Not much internal structure to be discerned, although it does appear slightly fainter in the centre than at the edges. No central star seen.250X Seeing standing up quite well, brightness at SW edge and darker centre confirmed. Brightens somewhat with OIII filter, reduced sense of darker centre, still softer on the NE edge than the SW. 500X is stretching the friendship tonight - visible, but quite blurred.

NGC 6822 GX in Sagittarius – Barnard’s Galaxy Type IB(s)m IV-V
19.1’x14.9’ mag 8.8 SB 14.8

135X A faint haze which appears quite a bit longer than wide (looking at the photo in NSOG, I think I can see the central bar but not all of the surrounding halo, hence the different sense of width than the above listed measurements would imply). A clump of about 8 foreground stars is seen at the SW end. The galaxy is reminiscent of a small, faint version of the Small Magellanic Cloud. The bar is quite distinct, fading gently and irregularly to the edges, with some larger bright and dark patches in the halo.

After a brief visit to Messier 22, whose beauty is beyond words, I come to

Messier 28/NGC 6626 GC in Sagittarius
Dia. 11.2’ mag 6.8 Class IV

175X Not quite as impressive as M22, but still quite a stunner, with a distinct core, many resolvable stars in across the core and spilling out across the halo. To the west of the core, there is a thick inverted U-shape gap in the spray of resolvable stars, with a haze of unresolved stars behind it. There is a matching parallel gap to the east of the core. Because the core is so distinct, there appears to be a slightly darker annulus around the core and the halo brightens beyond this, but my impression is that this is a bit of an illusion. Wide projections of haze spread out from the cluster to the south, north and east, northwest and west. These are not well defined.

NGC 6638 GC in Sagittarius
Dia. 5’ mag 9.1 Class VI

175X Just the other side of Lamda Sagittarii to M28, this GC looks about half the size and brightness of M28. Hints of resolvable stars, but they don’t jump out. Quite concentrated with a distinct core and fainter, very regular halo. Quite a spattering of foreground stars surround the GC.

NGC 6642 GC in Sagittarius
Dia 4.5’ mag 9.4

175X Significantly small and fainter than NGC 6638, on first view at a lower power the GC appeared to have a strange double core. At 175X a distinct core is visible, but there is a small bright patch just to the south east of the core. I can’t tell if this is a clump of resolvable stars belonging to the cluster or something in the foreground. The core is very distinct compared to the halo and the GC seems very concentrated.

NGC 6629 PN in Sagittarius
Dia 15” mag 11.3 Type 2a

250X This is one of those PNs that is easy to overlook as with direct vision it appears stellar. With averted vision, a bluish, soft-edged disc is apparent with observable central star. At first glance, the disc seems featureless, but with careful observation, I can make out a thin faint outer halo beyond the disc of the PN. OIII confirms the sense of the bright inner disc and a fainter haze of an outer shell.

NGC 6717 GC in Sagittarius, Palomar 9
Dia 3.9’ mag 9.2 Class VIII

175X Very small faint patch of haze near bright foreground star (nu2 Sagittarii). Some stars resolvable, but I think that these must be foreground stars. This reminds me of the many small knots of haze in the SMC. Little discernible detail due to the proximity of nu 2 Sagittarii. 250X shows little further detail, but the GC looks a bit less regular.

Messier 25/IC4725 OC in Sagittarius
Dia 32’ mag 4.6 Trumpler type I3m

90X A stunning sight – many bright stars, mostly bluish-white, but some of more yellow hue. The cluster seems to form a distorted W-shape. A narrow triangle of stars in the centre of the cluster points west and forms the cnetre of the W. Two sprays of stars join each side of the base of this triangle. One heads NW and the other SW. The northern edge of the centre triangle is missing some stars, so a narrow dark lane divides the cluster. The cluster looks about half a degree wide and 15’ across.

Messier 24 The Small Sagittarius Star Cloud + NGC 6603
95’x35’ mag 4.6

90X This instrument is probably not the best for observing this DSO. I find it very hard to define the edges of the cloud. It seems quite a bit larger than that specified in NSOG and listed above. A bright fuzzy patch of many faint stars may be NGC 6603, but again this looks too big. However it is in the centre of a triangle of bright stars, on apex of which is a double and this is consistent with the photo in NSOG. So I think I’m on track. Overall a very impressive bit of sky.

Messier 18/NGC 6613 OC in Sagittarius
Dia. 10’ mag. 6.9 Trumpler type II3pn

90X A bright little clump of stars which looks a bit like a distorted bow tie. At the centre of the cluster is a narrow triangle of stars reminiscent of a smaller version of the centre of Ara. Two wings of bright stars flank this. Mostly bluish-white stars.

Messier 17/NGC 6618 OC and emission nebula in Sagittarius – the Swan Nebula
20’x15’

135x One of my favourite DSOs, this occupies much of the FOV at this magnification. The graceful neck of the swan heads north, the water to the east and the fainter wings to the west. I note an intricate lacework of dark lanes where the neck joins the body of the swan. A fainter spread of more diffuse nebulosity trails the swan and again to me the nebula seems much larger than the 20’ listed. This nebula always has a very dynamic look to it, seeming to move across the sky and the more I look, the more subtleties I see.

NGC 6522/6528 GCs in Sagittarius
Dia 5.6/3.7 mag 8.6/9.5 Class VI/V

135X Both in the same FOV, 6522 looks twice the size and a magnitude brighter, they look about 20’ apart. Both small and faint GCs with no resolvable stars and both quite compact and concentrated. 175X Both still in one FOV. 6522 has a notable foreground star, distinct core and grainy appearance to its very regular, round haze. The brightness falls off fairly sharply from the core to the periphery. 6528 is very similar but fainter. Not quite as distinct a core and hence a less abrupt fall in brightness from the core to the periphery.

NGC 6624 GC in Sagittarius
Dia 5.9 mag 8.0 Class IV

175X Brighter and larger than 6522 but with no resolvable stars. It has a marked central core, it looks like a little 47 Tuc with its punctum of a core.

NGC 6565 PN in Sagittarius
Dia 9” mag 11.6 Type 4

250X Another PN that appears stellar with direct vision. Very small round bluish disc with no structure or central star discernible. OIII does not reveal any more detail, but the PN remains bright. NSOG suggests that this PN looks annular with OIII, but it looks if anything brighter in the middle to me.

NGC 6544 GC in Sagittarius
Dia. 8.9’ mag 8.1

175X Not very concentrated, this GC looks somewhat irregular in shape, squashed so that it is longer N-s than E-W. A string of faint resolvable stars runs N-S across the centre of the cluster. I suspect that these are foreground stars as the cluster is small and faint. It looks to me as if it’s had a few encounters with the disc of the Milky Way. It appears to have a small point projecting eastward from the centre of the GC. With the slightly flattened N-S appearance of the GC, this point makes it a little reminiscent of a thumbtack. Quite intriguing.

NGC 6553 GC in Sagittarius
Dia.8.1’ mag. 8.1 Class XI

175X Appears larger than 6544 to me and although it is of the same magnitude it looks less bright. I think this is because it is much less concentrated, has no core and an even distribution across the disc. A very regular cluster. 250X shows a grainier texture.

To conclude the evening, I visit epsilon Lyrae to split the double double, Jupiter and 47 Tuc. A most enjoyable evening.