May 12, 2010: The view through 48-inches

Steve Gottlieb

Last month Paul Alsing, Debbie Searle, Jeff Gortatowsky and I took a pilgrimage to Fort Davis, Texas and Jimi Lowrey's 48-inch scope, dubbed Barbarella, currently the largest amateur scope in the world. The scope was installed at Jimi's observatory (up a steep hill from a his house) by OMI (Optical Mechanics, Inc). We came close to canceling the trip a week before departure due to a medical emergency with Jimi's wife but he insisted we still visit and arranged for friend's Jim and Anna Chandler to step in as hosts and telescope operator. Besides drooling over the scope, we were given a personal VIP tour of inner workings of McDonald Observatory (http://mcdonaldobservatory.org/) by the director, Tom Barnes, and were led through all their facilities including the 433-inch HET (Hobbey-Eberly telescope), the 107-inch Harlan Smith telescope and the 82-inch Otto Stuve telescope). On another day, we toured the inside of the 82-foot VLBA radio telescope next to Prude Ranch by the dish operator, climbing right onto the edge of the center the dish (http://tinyurl.com/29vbtge).

The 48-inch f/4 mirror (actually 48.875", but who needs to nitpick) was produced by Lomo in Russia using Astro-Sital and is 5-inches thick with a weight of over 700 lbs. The steel/aluminum scope was built by OMI and the entire weight is roughly 3000 lbs. A custom built Servocat drives the scope with computer control through an ArgoNavis and a laptop. Still, at the end it just looks like your familiar truss-tube dob just seriously beefed up on some steroid/growth hormone concoction. Check out the photo of the scope at http://www.wildcard-innovations.com.au/images/barbarella1.gif and a feature article is at http://tinyurl.com/2euqyov. OMI also details building and installing the scope at http://tinyurl.com/2ahy9av.

We never pushed the scope to superhigh magnifications, but at 700x the optical performance was stunning with sharp, tiny stellar images down to 18+ magnitude. The mag 16.5/16.7 components of the Twin (gravitationally lensed) Quasar in Ursa Major were so easily resolved (6" separation) you really couldn't consider this any kind of challenge object with this scope. All 5 components of the HCG 55 chain were easily resolved (mag 15.9-17.1) and a more serious challenge, HCG 50, was pretty easily resolved into 4 distinct components with the tiny individual galaxies from mag 18.7 to 19.6B.

Unfortunately, the weather was mostly cloudy and we really only had one good night out of five with another couple of hours on a second night. Still, we had a pretty good taste of how his 48" scope performs in very dark skies. We never pushed the scope to superhigh magnifications, but at 700x the optical performance was stunning with sharp, tiny stellar images down to 18+ magnitude. The mag 16.5/16.7 stellar components of the Twin (gravitationally lensed) Quasar in Ursa Major were so easily resolved (6" separation) they reminded me of observing the double star, M73, in a small scope. All 5 components of the HCG 55 chain were easily resolved (mag 15.9-17.1) and a more serious challenge, HCG 50, was pretty easily resolved into 4 distinct components with the tiny individual galaxies from mag 18.7 to 19.6B. In the end, there really wasn't one "challenge" object that turned out to be a real challenge!

On the night we observed, the skies were clear but there was pretty heavy dew which probably cut down on the transparency, nevertheless the SQM reading was ~21.75 (his house is down the road from Prude Ranch, where the Texas Star Party is currently taking place). Early in the morning, Jim and I went back to observe when the relative humidity was drier and I believe the SQM reading was probably closer to 21.85. I was initially a little intimidated by the thought of climbing up a huge ladder at night, but after one trip up and seeing how rock solid it was, it wasn't an issue. Jim Chandler, was a whiz at operating the scope through SkyTools and with his assistance we maximized the available time to see quite a few objects. The following represents roughly 1/2 the fields I looked at with the 48-inch, but gives a pretty good flavor of the views --

1)   NGC 2359 = Thor's Helmet
07 18 31 -13 13.5
Size 8'x6'

The 5' central region of Thor's Helmet was a mesmerizing at 267x and 330x (unfiltered).  There is a large, bright knot at the south end of the rim where the inner portion of the bright wing that heads southwest connects with the central bubble.  Along the northern edge of the rim are three collinear mag 11 stars (2.2' length) oriented E-W. The rim of the bubble is noticeably brighter in a thin arc beginning due north of center (between the two western stars) and extending about 90° clockwise to the west (this portion of Thor's Helmet is listed separately as NGC 2361).  The rim is also brighter along a 45° thicker arc on the southeast side.  The rim has a lower surface brightness on the east and NE side and varies in thickness and brightness around the entire bubble, enclosing a darker central region

Three brighter stars (nearly collinear) and several fainter stars are superimposed within the main bubble.  A second, smaller, incomplete bubble just north of center outlines an inner dark "hole", which includes one of the brighter stars.  The ionizing Wolf-Rayet star HD 56925 is at the southwest edge of this inner bubble.  Additional thin wisps of nebulosity crisscross the central region.
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2)   UGC 3697 = "Integral Sign" Galaxy
07 11 22.6 +71 50 10
V = 12.9;  Size 3.0'x0.2';  Surf Br = 12.3;  PA = 76d

The Integral Sign galaxy was carefully observed at 510x.  This superthin galaxy extended 3.3'x0.15' E-W for roughly a 22:1 axial ratio!   Near the west end of the galaxy there is a noticeable hook towards the northwest as the galaxy fades to and ends at a very faint star or knot.  The low surface brightness portion near the west end has irregular, streaky appearance with an impression of knotty structure near the very tip.  At the eastern end there is a much more gradual, subtle bending so that the eastern tip is pointing due east, although the central portion of the galaxy is WSW-ENE.  There is a faint star just off the north side, slightly west of center and a second star is off the south side where the hook begins on the western side.
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3)   M66
11 20 15.0 +12 59 22
V = 8.9;  Size 9.1'x4.2';  Surf Br = 12.7;  PA = 173d

This showpiece galaxy stretches 7'x3' N-S.  The central region is dominated by prominent, 3'x1.2' central bar that is elongated NNW-SSE.  The central region has a mottled, irregular surface brightness and increases gradually towards the center and then suddenly to a very bright, stellar nucleus.  A very faint star or knot was seen at the very north tip of the bar.  The longer, better defined arm is attached at the north end and sweeps directly south along the western flank of the galaxy for a total length of ~5'.  The western edge of this arm is very well defined as it fades to the southern tip, though the inner edge merges with the glow within the central region.  The arm and bar are brightest where they merge at the north end of the central region. The second spiral arm is attached at the south end of the bar and shoots north on the eastern side of the galaxy.  This arm fades after a shorter distance, so is not as prominent, but is brightest near at the southeast as it emerges from the bar.  A mag 9.8 star lies 3' NW of center at the outer edge of the halo.
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4)   NGC 2438/M46
07 41 50.6 -14 44 07
V = 11.5;  Size 73"x68"

At 700x, NGC 2438 was a beautiful "cheerio" ring with a with a sharply defined rim of 1.2' diameter and a fairly large, dark central hole of 25-30".  The mag 12.8 star in the center was prominent with a second mag 14.5 star ~15" SW of center.  A third mag 16 star was just inside the annulus on the SE side, ~20" from center.  The rim had a very uneven surface brightness with an impression of some radial streaks and one or two additional faint, embedded stars.  The rim was noticeably brighter along the NE quadrant and to a slightly lesser extent along the opposite SW portion of the rim, creating a bipolar appearance.  A bright mag 11 star is just off the SE side and the planetary floats in the beautifully rich star field of M46.
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5)   NGC 2403
07 36 54.5 +65 35 58
V = 8.5;  Size 21.9'x12.3';  Surf Br = 14.4;  PA = 127d

This amazing multi-arm spiral stretched across the entire 15' at 330x, with the major axis running NW to SE.  The spiral arms are striking with the more prominent arm attached near the NW end and sweeping counter-clockwise 180° along the northern side of the galaxy, tapering as it extends to a point roughly 5' SE of the core.  This arm is widest near the NW end, where it begins sweeping east.  A second inner arm attaches near the SE end of the main body and hugs tightly along the southern side of the galaxy as sweeps to the NW side.  A more ill-defined branch heads west from the SE end past a mag 11 star situated 2' WSW of the core.  The field was too small to trace out the outer arms.  Numerous splotches of HII regions stained the surface and I only had time to quickly sketch the most obvious knots.

The supergiant HII complex NGC 2404, located 1.7' ENE of the core and 1.5' NNW of a superimposed mag 10.5 star, appeared as a very bright, irregular, 20" knot.  On the NW side of the galaxy is a collinear string of 3 stars oriented NE to SW with an obvious knot along this line an additional 50" SW (catalogued as #44 in "Optical HII Regions in NGC 2403", A&A, 237, 1990).  Just north of the core are two HII knots, separated by 45" and both 12" in size.  The western knot is catalogued as #174 and the eastern knot as #224.

On the SE side of the galaxy is a pair of HII knots separated by 40".  The eastern knot is #346 and is situated 1.6' SE of the mag 10.5 star and the western knot includes #221.  At the SE end of the spiral arm which contains NGC 2404 is another 10" knot, catalogued as #348/351/352.  It can be pinpointed 1.0' NE of the mag 10.5 star.  On the SE end of the galaxy a fairly faint, irregular knot (#331) was noticed 1' W of a mag 14 star.
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6)   NGC 2537 = "Bear-Paw" Galaxy
08 13 14.5 +45 59 31
V = 11.7;  Size 1.7'x1.5';  Surf Br = 12.6

At 624x, the view of the highly irregular "Bear-paw" galaxy (Arp 6) was fascinating.  The galaxy is fairly large, roundish, 1.5' diameter and is broken up into bright knots and arcs that border a large curving dust lane that winds through the glow and traces out a dark "U" inside the galaxy.  The main bright regions form the three "toes" of the Bear-paw.  On the NW side, the first "toe" consists of the brightest knot, ~0.3' diameter, with a second smaller and fainter knot close south.  The entire glow from this "toes" is ~30".   In the center is a brighter core, ~0.3' diameter, which is nearly isolated by the obscuring dust, but the glow extends to the south end of the galaxy where it brightens slightly at the rim, forming the middle toe.  The third toe is on the following side of the galaxy (~0.3' diameter) and is less prominent, though slightly brighter due due east of center.   The curving "U"-shaped dust channel enters the galaxy both west and east of the middle toe in two parallel lanes and curves around the core, forming a noticeable arc on the north side of the core.

NGC 2537A (mag(B) = 16.4) was picked up just 4.5' due E of the center of NGC 2537.  It appeared fairly faint, fairly small, round, weak central brightening.  A mag 13.5 star lies 1.2' S and a mag 15.4 star is 57" WSW.
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7)   IC 2233
08 13 59.0 +45 44 38
V = 12.6;  Size 4.7'x0.5';  Surf Br = 13.3;  PA = 172d

This remarkably thin, beautiful superthin edge-on extends 4.0'x0.25' (~15:1 axial ratio) NNW-SSE.  Contains a brighter elongated central region with a slightly brighter nucleus (though no bulge).  The overall surface brightness is fairly low and the galaxy gradually dims near the ends of the extensions.  The center is situated only 0.9' SW of a mag 10 double (a mag 13.5 companion lies 13") and the orientation aligns with the center of the galaxy.  Roughly midway along the northern extension is a mag 14 star.  Beyond this star the galaxy gradually fades to the tip, extending to within 0.6' of a faint star off the NNW tip.  On the south extension, the galaxy also fades, but after nearly dimming out there is a feeble glow at the very tip, which is slightly angled or bent towards the east.  Located 17' SE of the Bear-Paw galaxy.
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8)   M81/Holmberg IX
09 55 33.2 +69 03 55
V = 6.9;  Size 26.9'x14.1';  Surf Br = 13.2;  PA = 157d

Dazzling view of M81 at 267x (21mm Ethos) and 330x (17mm Nagler).  The galaxy is elongated 2:1 NNW-SSE and extends at least 20'x10'.  The brightness level increases gradually to the center from the large, very bright oval core but is punctuated at the center by an extremely bright, quasi-stellar nucleus.  A bright spiral arm attaches to the galaxy on the NW end and bends abruptly to the south, passing across a mag 12 star located 5' NW of center.  As it heads southeast, the arm separates from the main glow of the galaxy and can be traced as it passes just north of Struve 1387 (10.8/10.8 at 9"), ending to the NE of a striking double star, Struve 1386 (9.3/9.3 at 2.1").  The total length of this arm is ~15'.  The second main arm is more prominent, attaching to the main body on the south end.  This arm is much brighter in a narrow arc as it curves around at its south end.  As it then sweeps NNW, this arm is relatively narrow with a very well defined edge, and gradually separates from the main body.

Holmberg IX is a dwarf irregular located just 10.5' E of the center of M81 and the outer halo of M81 was visible near the edge of the field.  At 330x it appeared very faint, fairly large, 2' diameter, round, low even surface brightness with no noticeable concentration.  The galaxy is nestled within a kite asterism including a mag 13 star 1.3' S.

This M81 companion was discovered by Sidney van den Bergh in 1959 and is similar to IC 1613.  Holmberg IX has the youngest mean stellar population age of any nearby galaxy and may be a young tidal dwarf assembled from gravitational collapse of gas and stars stripped off during the last close encounter of M81 with M82 (see http://arxiv.org/PS_cache/arxiv/pdf/0802/0802.4446v1.pdf)
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9)   M82
09 55 53.5 +69 40 54
V = 8.4;  Size 11.2'x4.3';  Surf Br = 12.5;  PA = 65d

At 330x numerous irregular dark rifts were visible slicing up the mottled, clumpy surface.  Very small, bright knots or condensations are just west of a dark wedge that pierces the galaxy on the south side and tapers as it cuts across the center at an oblique angle.  The very bright section of the galaxy to the NE of the dark absorption wedge also displays mottled structure.  Another prominent dark inclusion cuts into the galaxy from the north on the northeast side of the galaxy.  A very faint extension of low surface brightness haze bulges out from the main portion of the galaxy on the south side.  This glow is west of the dark wedge and east of a mag 10.5 star located 5.8' SW of center. On images this large bulge appears to explode out from the galaxy with filamentary structure.  Overall, there was too much visible structure to describe from a couple of minutes at the eyepiece.
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10)   Double Quasar = Q0957+561
10 01 20.8 +55 53 53
V = 16.5; 6" separation

The gravitationally lensed Twin Quasar was very easily split in the 48" at 700x.  At this magnification, the two components, separated by 6" were widely split with lots of clean space between the quasar images.  The individual components appeared as perfectly sharp mag 16.5 and 16.7 stars oriented ~N-S, with the slightly brighter "A" component (delta mag = 0.2) to the north.  At a redshift of z = 1.41, the distance to the Double Quasar is roughly 9 billion light years.
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11)   M97 = Owl Nebula
11 14 47.7 +55 01 08
V = 9.8;  Size 202"x196"

The Owl Nebula was quite impressive at 330x (unfiltered) and exhibited a fascinating amount of detail.  The mag 16 central star was easily visible at the center of the 3.4' disc.  To the NW and SE of the central star are two large, darker "holes" (Owl's "eyes"), each roughly 45" in diameter.   The SE eye has a little more contrast and a very faint star is close to its SE edge.  The NW eye is a little larger, though not quite as dark in the center.  A mag 12 star lies 2.6' NE of center and a mag 14 star lies 3' S of center.

MCG +09-19-014 (mag(B) = 16.1) is located just 3.8' SSE of the center of M97.  It was easily visible in the field at 330x as a fairly faint, small glow elongated NW-SE with a fairly low surface brightness.  A mag 14 is at the north edge of the glow and detracts from viewing the galaxy.
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12)   HCG 50
11 17 06 +54 55.3
Size 0.6'x0.4'

Four members of HCG 50 = Shkh 5 from mag 18.7(B) to 19.6(B) were visible at 623x and 701x.  Three members were seen immediately at 623x and the 4th picked up and sketched at 701x (without prior reference to an image).  All 4 of these galaxies were very small (at most 10" diameter) and crammed into a region measuring 39"x24".  The field of HCG 50 is located just 21' ESE of M97.  This is a very distant group with a redshift of z = .139, corresponding to a distance of ~1.9 billion light years (nearly twice that of the Corona Borealis cluster).

50A: at 700x appeared very faint, very small, 10" diameter.  Just 16" E is HCG 50B.  Situated 20" NE of a mag 16 star.

50B: the "B" component of HCG 50 lies 16" E of 50A (closest member) and 35" NE of a mag 16 star.  At 700x, it appeared very faint and small, roundish and a little fainter than 50A.  No elongation was noted.

50C: the "C" component lies 27" N of a mag 16 star and 25" NW of 50A.  This was a difficult object at 700x (faintest of 4) with a low surface brightness and less than ~6" diameter.

50D: the "D" component was the third brightest of 4.  At 700x it appeared extremely faint and small, ~6" diameter.  Forms the northern vertex of an equilateral triangle with 50A (22" S) and 50C (24" SW).

2MASX J11165388+5456268 (B = 16.5) was picked up in the same high power field as HCG 50.  At 700x, it visible as a faint, very small glow just 15" NW of a mag 13 star.  HCG 50 lies 2.3' SE.
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13)   HCG 55
11 32 07.0 +70 48 56
V = 14.9;  Size 1.1x0.3

I was surprised to find that all five members were visible without much effort at 700x, which cleanly resolved the 1.1' N-S chain into five "knots", strung out like beads on a necklace.  While at the eyepiece, I carefully described the relative placement of all the components to Jim Chandler, who verified the descriptions using the DSS image on a laptop.

55A: at 700x, the brightest member of the HCG 55 (UGC 6514) chain appeared moderately bright, slightly elongated, small, ~15"x12".  This galaxy is the middle of 5 in the 1.1' chain with 55E 12" N and 55C 19" S.

55B: southernmost member of five in the chain and second brightest.  It was easily visible as a fairly faint, very small knot, ~10" diameter.

55C: this member of HCG 55 was the 4th of five in terms of visibility at 700x and appeared very faint and small, with a low surface brightness halo that faded out into the background.  Squeezed between 55A 19" N and 55B 15" S.

55D: northernmost galaxy in the 5-member galaxy chain (total length 1.1').  It appeared faint, very small, round, ~8" diameter.  In terms of visibility, I placed this member as 3rd of 5.

55E: this galaxy was the smallest and faintest (B = 17.4) of 5 in the HCG 55 chain.  It appeared extremely faint and small, round, ~4" diameter.  Sandwiched between 55D just 9" NNW and 55A just 12" SSW!  This galaxy has a discordant redshift (over twice the redshift of the other 4 members), so appears to be a superimposed member, though it is situated right along the chain.
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14)   Terzan 1

17 35 47 -30 28.9
V = 15.9,  Size 2.8

This was the last challenging deep sky object observed as twilight was beginning and the east was quickly brightening.  Once the field was identified, Terzan 1 was immediately picked up at 330x in a very rich star field as a fairly faint, ill-defined glow, situated between two mag 10 stars that were separated by 2.5'.  The glow was mottled with a few very faint stars superimposed.  At 624x, the globular lies just west of the line (SSW-NNE) connecting the two stars; 1.2' from the brighter star (V = 9.7) to the NE and 1.7' from the mag 10.0 star SSE.  The globular appeared fairly small, 1.5'-2.0' diameter, and extended nearly to the star to the NE.  At this magnification, at least half–dozen very faint stars were resolved over the glow.  Several brighter stars were scattered around the periphery of the cluster, though these appeared to be field stars as they seemed too bright to be cluster members.

This highly reddened bulge cluster has the smallest projected distance of any globular to the galactic center (2.7°).  According to an HST study in 1999, the brightest members in the central part of the cluster are V = 18.5 with V(HB) = 21.4.