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Old 22-11-2011, 05:52 PM
SteveG (Steve)
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SteveG is offline
Join Date: Jan 2010
Location: Berkeley, CA, USA
Posts: 39
Observations with a 48-inch dob (part 2)

Here's a continuation of the first part of the observing report with Lowrey's 48-inch dob.

NGC 1365
03 33 35.9 -36 08 24
V = 9.6; Size 11.2'x6.2'; Surf Br = 14.1; PA = 32d

Stunning view of this huge, barred spiral with the full extent of the long, graceful arms clearly visible and a great deal of structure. The very bright bar runs nearly 3' WSW-ENE and contains an extremely bright core that increases to a striking knotty nucleus that is sliced by a dust lane running SW to NE. The dust lane creates a mini spiral in the center with a bright elongated section south of the lane that has an "arm" attached at its NE end that curls to the southwest. The section of the nucleus north of the lane appears as a small but brighter arm, gently curving from SW to NE.

The main northern arm is attached at the west end of the bar and has a bright, mottled "knot" as it emerges from the bar and heads NNE. This knot contains the HII regions #23-25 from Paul Hodge's 1969 "HII Regions in Twenty Nearby Galaxies" (ApJS, 18, 73). It was also the site of SN 2001du, a supernova discovered visually by Robert Evans. The arms dims a bit and then brightens along a 1' strip just northwest of a superimposed mag 13.5 star. The arm then dims significantly but can be easily traced a total length of 6.5', ending just SE of a mag 13.5-14 star.

The main southern arm emerges on the ENE of the bar as a brighter patch or OB association which contains [H69] #2-3, matching the west end. A group of stars is just east, beyond this patch. The arm extends ~6.5' SW and is bordered by several stars; a mag 14.5 star on the south edge before the middle of the arm, a mag 16 star 1.3' due S of this star and two mag 15/16 stars on the inside (northern edge) beyond the middle of the arm. A very small, very faint knot is near the SW tip of the arm. The arm dims significantly at this point but bends and continues another 2' NW.

NGC 1532/31
04 12 04.3 -32 52 29
V = 9.9; Size 12.6'x3.3'; Surf Br = 13.8; PA = 33d

This showpiece edge-on stretches 7'x1.2', tilting SW-NE. The galaxy is sharply concentrated with a large, elongated, very bright core that is mottled and increases to the center. The surface is knotty, streaky and mottled and a striking dust lane runs along the major axis, unequally slicing the galaxy into two parts to the south of the core. The dust lane expands to a larger, elongated patch on the NE side of the core. The section to the south of the dust lane is much thinner and increases to a prominent, very bright knotty 1.5' streak on the SW end. A very faint star (B = 18.2) is close to the SW tip. The southern strip near the core is fainter than the main section above and appears more patchy due to dust. Just NW of the core is NGC 1531, a bright elliptical that angles perpendicular to the core and forms a striking pair. NGC 1531 appeared very bright, moderately large, oval ~2:1 NW-SE, 1.2'x0.7', well concentrated with a very bright core.

NGC 1961
05 42 04.4 +69 22 46
V = 11.0; Size 4.6'x3.0'; Surf Br = 13.7; PA = 85d

At 375x, this distorted spiral appears very bright, very large oval nearly 2:1 E-W, ~3.6'x2.0', highly asymmetric appearance. Contains a very bright, large oval core that is clearly is offset to the north side of the galaxy! A large arm sweeps E-W along the south side of the halo. A broad dust lane runs parallel to the arm on the inside. Surrounding the core are shorter inner spiral arms including an arm just north of the core that sweeps west and bends south. A mag 13.5 star is superimposed just inside the dust lane, 30" SSE of center.

NGC 6695
18 42 42.9 +40 21 59
V = 13.5; Size 1.1'x0.7'; Surf Br = 13.1; PA = 12d

This excellent two-armed barred spiral appeared fairly bright, moderately large with a slightly curving "bar" that is elongated 2:1 SSW-NNE, ~0.6'x0.3'. Contains a slightly brighter, elongated core. An arm emerges from the NNE end of the bar and curves clockwise, bending NW towards a mag 15.5 star and fading out just before intersecting the star. The second arm is attached at the SSW end extending south, though dimming out rapidly before reaching a mag 16 star off the south end. Overall, the galaxy has an elongated "S" appearance.

NGC 6946
20 34 52.3 +60 09 14
V = 08.8; Size 11.5'x9.8'; Surf Br = 13.8

This very bright, showpiece face-on spiral stretches roughly 9'x7 E-W. At 375x, four arms were visible, each containing one or more HII regions. The brightest arm is attached on the west side of the central region and curves counterclockwise to the north and then heads east, passing just south of a mag 13.5 star and spreads out to the NE of the central region. At the eastern tip (4.2' from center) is a bright HII knot of 12" diameter, catalogued as #3 under NGC 6946 in Paul Hodge and Robert Kennicutt's 1983 "Atlas of HII Regions in 125 Galaxies" (AJ, 88, 296). A second shorter arm emerges from the core on the north side, and rotates more sharply around the galaxy on the north side, passing south of the brighter arm, and curving around to the east side. It contains #63-76, an elongated knotty HII complex at its end situated 2.5' due E of center.

On the west side are two additional arms, though the brighter inner arm is better defined. It begins on the south side of the central region and curls sharply to the north on the west side. It passes through a few mag 14 foreground stars and nearly fades out 3.2' NW of center. A dim extension finally ends 3.5' N of center at #285, a very faint, very small knot inside a triangle of stars. An outer arm on the south side rotates towards the west and intersects #503-507, a very bright, round knot of 20" diameter, that rivals the inner core in size. Using a Using a DGM Optics "Galaxy Contrast" filter, the core was dimmed more and the knot appeared nearly as bright. Studies reveal this feature is a circular bubble containing numerous, tightly packed small clusters and a bright supermassive star cluster that resembles a young globular. After this point, the arm becomes more patchy as it spreads to the northwest but near the end is #527-528, an extremely faint knot just west of a mag 14 star 3.5' NW of center.

NGC 7479
23 04 56.7 +12 19 23
V = 10.8; Size 4.1'x3.1'; Surf Br = 13.4; PA = 25d

This is probably the best barred spiral in the northern sky. At 488x and 610x the central bar is very bright and extends over 2' N-S. The bar has a mottled appearance, bulges slightly in the center, broadly concentrated with a small bright core. A bright mag 12.5 star is at the north end of the bar, 1.3' from the center. At this end an arm emerges from the bar, beginning to curve counterclockwise to the east, but abruptly dims and merges with the halo on the east side. At the south end of the bar, a beautiful sweeping arm wraps counterclockwise around the south of a superimposed mag 13.5 star, extending to the west side of the core. This prominent arm dims and ends just north of an extremely faint HII knot (stellar) in the arm, which is catalogued by Rozas in the 1999 A&AS paper "Global properties of the population of HII regions in NGC 7479 from photometric Halpha imaging" as region #4. A mag 16.4 star is 0.7' due west (outside the arm) of this knot. A mag 15.7 star is also superimposed between the faint HII knot and the bright star at the north end.

NGC 7814
00 03 14.9 +16 08 43
V = 10.6; Size 5.5'x2.3'; Surf Br = 13.2; PA = 135d

375x and 488x provided a great view of this showpiece edge-on spiral. The oval central bulge is large and very bright, increasing to an intense core. A very thin, very high contrast dust lane slices through the major axis of the galaxy, neatly bisecting the galaxy. On close inspection, the halo on the south side of the lane is marginally more extensive. At the center, a small nucleus is apparently obscured, leaving only two very small brilliant "knots" on either side of the lane. Beyond the central region, much fainter arms extend NW and SE, increasing the total size to 5'x1.5'. The dust lane is easily visible splitting the edge-on arms until they dim out at the tips.

Steve Gottlieb
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