OR: Double the fun -- Lake Sonoma on 2/13 and 2/15.
by Steve Gottlieb
On both Tuesday Feb 13 and Thursday Feb 15 I drove up to Lake Sonoma and met a few other local amateurs looking to take advantage on the excellent observing conditions we had in the Bay Area during mid-February. When I headed out from Berkeley on both days, the afternoon skies were unusually deep blue and the hills of Marin were sharply etched in the distance. Despite hitting the early part of the afternoon commute up 101, I made it up to Healdsburg relatively quickly, exited at Dry Creek Road, and was immediately driving through rolling hills and a long contiguous stretch of Sonoma County vineyards. Soon I was up at Lake Sonoma, a few miles west of Geyserville, where the western skies (as well as the northern) are quite dark. As is often the case this time of year, on both nights we were treated to a spectacular zodiacal cones in the west, angling up towards Taurus.
On Tuesday I was joined by Bob Douglas, who brought along his 28-inch, and Dan Smiley, who went lightweight with a TeleVue TV-76 and binoculars. When I returned on Thursday, Carter Scholz also attended with his homemade 16-inch and Ray Howard brought along his beautiful 12.5-inch f/6 New Moon telescope.
Both nights I took a look at supernova SN 2018gv in NGC 2525 (Puppis) and SN 2018pv in NGC 3941 (in Ursa Major). The first was 13th magnitude and easily seen at the southwest edge of the galaxy [50" west and 39" south of center]. The Puppis star field was rich, but 2018gv was the brightest star close to the disc of the galaxy. SN 2018pv was also 13th magnitude, but is located only 4 arcseconds east of center, bumped right up against the edge of the bright nucleus. At 200x I could immediately see a brighter spot on the east side of the nucleus and at 375x the core increases to a very small, quasi-stellar nucleus. The supernova almost looked like a close double star with the nucleus.
Overall, conditions were excellent on both nights my SQM-L readings hit 21.5 MPSAS (magnitude/square arcsec), about as dark as it gets at Lake Sonoma. As an example, Ive observed the Horsehead Nebula a number of times from this site, and although it's generally visible in a variety of conditions through my 18 and 24 scopes using a H-beta filter, on Thursday night the extended strip of nebulosity (IC 434) containing the Horsehead was immediately seen unfiltered at 124x and the Horsehead notch was definite, no need for a filter (although of course it did add contrast when inserted). Same result with a portion of Barnards Loop. As far as other targets, Ive combined observations from both nights into my 10 favorites eyepiece fields.
NGC 1275 is a peculiar galaxy at the heart of the Perseus Galaxy Cluster (Abell 426), roughly 250 million l.y. distant. This active radio galaxy is one of the 6 galaxies studied by Seyfert in his seminal 1943 paper "Nuclear Emission in Spiral Nebulae. Deep images reveal an extraordinary web of lacy filaments, dust lanes and bursts of star formation. This dusty material is thought to belong to a foreground edge-on spiral that is falling in and colliding with the larger elliptical.
Visually, Abell 426 is one of the richest galaxy clusters for amateurs, though the setting a Perseus star field bespangled with fainter stars makes picking out the small members challenging. An 8-inch will reveal a few of the brightest members, but the cluster really comes alive in 12-inch and larger scopes. The central core of the cluster is elongated in a 45 string trending northeast to southwest, and includes over a dozen NGCs along with a number of fainter galaxies. The rich nucleus of the cluster shown above in this SDSS image is only 9 arc minutes across. All of these labeled galaxies were logged in one high power field (375x) in my 24-inch, though in superb conditions an 18-inch should also do the trick. Galaxies with labels starting with N are NGCs and for all others Ive used P for PGC designations.
At 375x, I logged NGC 1275 as bright, fairly large, slightly elongated WNW-ESE, ~1.6'x1.3. Three distinct zones were evident; a strong bright core, a prominent quasi-stellar nucleus and a halo that gradually fades out. NGC 1275 is similar or slightly smaller in size to NGC 1272, but has a higher surface brightness core/nucleus. A mag 13.8 star is just off the NW side. A dozen members of AGC 426 were logged within only 5' of NGC 1275! The closest is PGC 12441, 1.5' northeast of center.
As you explore outside the central 1° region, the density of galaxies thins out but members are spread out over 3° or more of the sky. Albert Highe compiled a table of 350 galaxies within 4° from NGC 1275 and observed over 300 of these with a 17.5-inch scope (see http://pw2.netcom.com/~ahighe/a426.html). On an even larger scale, Abell 426 is part of the Pisces-Perseus Supercluster, one of the largest known structures in the universe. This celestial filament of galaxy clusters (an immense sheet viewed edge-on) stretches across 40° of sky from the Perseus Custer through the rich clusters Abell 347 and Abell 262 in Andromeda and continuing west-southwest to the NGC 507 and NGC 383 galaxy groups in northern Pisces.
This unusual 10" pair was discovered by Dutch Roman Catholic priest and astronomer Johan Stein in 1908. It consists of a mag 11.1 red dwarf (Stein 2051A) and a mag 12.4 white dwarf (Stein 2051B), at a distance of only 18 light years. This HST image shows only the white dwarf component (bluish color), along with a very close but distant field star. At 10 separation, the red and white dwarf pair were very easily resolved at 200x. The brighter red dwarf component on the southwestern side had a reddish hue with careful examination. The duo has a large proper motion, but is located ~9' E of mag 8.9 HD 28176.
Stein 2051 B is the 6th nearest white dwarf to the Sun after Sirius B, Procyon B, van Maanen's star, LP 145-141 and 40 Eridani B. Remarkably in 2017 Stein 2051B was observed using the HST passing in front of a more distant star about 5,000 light-years away. The HST news blurb reads
"Looks can be deceiving. In this Hubble Space Telescope image, the white dwarf star Stein 2051 B and the smaller star below it appear to be close neighbors. The stars, however, reside far away from each other. Stein 2051 B is 17 light-years from Earth; the other star is about 5,000 light-years away.
Astronomers made the Hubble observations of the white dwarf, the burned-out core of a normal star, and the faint background star over a two-year period. Hubble observed the dead star passing in front of the background star, deflecting its light. During the close alignment, the distant starlight appeared offset by about 2 milliarcseconds from its actual position. This deviation is so small that it is equivalent to observing an ant crawl across the surface of a quarter from 1,500 miles away. From this measurement, astronomers calculated that the white dwarf's mass is roughly 68 percent of the sun's mass.
"Gravitational deflection of starlight around the Sun during the 1919 total solar eclipse provided measurements that confirmed Einsteins general theory of relativity. We have used the Hubble Space Telescope to measure the analogous process of astrometric microlensing caused by a nearby star, the white dwarf Stein 2051 B. As Stein 2051 B passed closely in front of a background star, the background stars position was deflected. Measurement of this deflection at multiple epochs allowed us to determine the mass of Stein 2051 B the sixth nearest white dwarf to the Sunas 0.675 ± 0.051 solar masses. This mass determination provides confirmation of the physics of degenerate matter and lends support to white dwarf evolutionary theory.
UGC 2773 is a member of the IC 342/Maffei I group and is heavily obscured by dust in the Milky Way. Youll notice the reddish color to the Milky Way field stars in this SDSS image. At 282x the galaxy appeared fairly faint, moderately large, irregularly round, ~1' diameter, with a fairly low but uneven surface brightness. At 375x some slightly brighter regions caught my eye for brief moments though they appeared to be off center. The galaxy is located in a field rich in fainter stars 7' southeast of mag 6.8 HD 21641, 14' south of mag 5.5 HD 21699 and just 20' southeast of mag 4.3 Sigma (35) Persei.
UGC 2773 contains UGC 2773-OT, a remarkable 19th magnitude supernova imposter that resembles the 19th century eruption and behavior or Eta Carina (chronicled by John Herschel over several years in the 1830s and 1840s from the Cape of Good Hope). It was discovered in 2009 and the subject of a 2016 study titled "The Persistent Eruption of UGC 2773-OT: Finally, a Decade-Long Extragalactic Eta Carinae Analog. The study found ...
"While SN impostors resemble the Great Eruption of Eta Car in the sense that their spectra show narrow H lines and they have typical peak absolute magnitudes of -13 to -14 mag, most extragalactic events observed so far are quite different from Eta Car in duration. Their bright phases typically last for roughly 100 days or less, rather than persisting for several years. The transient object UGC 2773-OT had a similar peak absolute magnitude to other SN impostors, but with a gradual 5-yr pre-discovery rise. In the 6 years since discovery, it has faded very slowly (0.26 mag/yr). Overall, we suggest that its decade-long eruption is so far the best known analog of Eta Car's 19th century eruption.
NGC 2943 is the brightest in the WBL 229 group, which includes nearby NGC 2941 2.3' WNW, LEDA 3744883 1.5 E, NGC 2946 6.8 E and more. NGC 2943 appeared moderately bright and large, oval 5:3 NW-SE, ~40"x24", well concentrated with a small bright core. A mag 15.5 star is 40" SW of center and a mag 15.2 star is 50" SE. NGC 2941 was faint, small, slightly elongated, 20"x15, with a low even surface brightness. LEDA 1523095, squeezed between NGC 2943 and 2941, appeared extremely faint (B = 16.7) and small, round, 8" diameter. NGC 2946 (note the warped appearance on the SDSS image) was fairly faint, elongated 3:1 SSW-NNE, 0.6'x0.2', low even surface brightness.
UGCA 90 = ESO 550-24
This barred spiral has a rather chaotic photographic appearance and has been classified as a Magellanic Irregular. The superimposed star to the right of center is only 13th magnitude, but still detracted from my view. Using 200x, the galaxy appeared fairly faint, elongated 2:1 NW-SE, ~2'x1', broad weak concentration with an ill-defined core. The low surface brightness halo fades into the background so it was difficult to estimate the total size, but most of the galaxy appeared east and south of a superimposed mag 13 star.
NGC 2929 is the first in a nice equally spaced and collinear triplet and brightest in a group (WBL 227) that includes NGC 2927, 2930, 2931, PGC 27435 and PGC 27434. The distance is ~350 million l.y. and the galaxy hosted a supernova in 2010 (SN 2010jn). NGC 2929 was moderately bright, elongated 3:1 NW-SE, 0.9 x 0.3', slightly brighter bulging core.
NGC 2930 is a blue emission-line galaxy (WAS 1) less than 3 north of NGC 2929 and was also the site of a recent supernova (SN 2005M). I found it the faintest in the trio with NGC 2931 and noted as fairly small, roundish, 30" diameter, low even surface brightness.
PGC 27435, located 5.6' E of NGC 2929, was extremely faint (V = 15.6), fairly small, elongated 2:1 ~E-W, ~25"x12. It was often visible at 225x (10mm ZAO) and 375x (6mm ZAO), but I couldn't hold it steadily for a significant length of time. PGC 27434 was marginally glimpsed 1.2' ESE of PGC 27435. I probably only noticed the slightly brighter central region (~10") and it was too ephemeral (V = 16.1) to notice a shape.
This blue dwarf is located in the northern end of the obscure constellation Caelum and resides at a distance of roughly 55 million light years. At 200x I found a faint, moderately large, glow that was slightly elongated. The surface brightness was very low and there was only a very weak concentration with no core or nucleus. It was difficult to estimate the size but extended roughly 1.6'x1.3. Bumping the power to 282x, a slightly brighter central region was more evident but there was no additional features. A triangle of mag 12-13 stars is directly east.
UGC 1817 = FGC 280
This late-type superthin spiral appeared as a very faint, ghostly sliver, ~10:1 NNW-SSE, ~1.2'x0.1', slightly brighter central region but overall very low surface brightness, fades out at the tips. There was no central bulge at all. Although often visible, I couldn't hold UGC 1817 continuously as it popped in an out of visibility. The bright star in the image is 3 southwest and mag 10.3. A fainter mag 12.5 star is 1.6' NE. UGC 1817 is part of the NGC 877 group, centered 55 NW.
This galaxy is included in Alvin Hueys Observing Flat Galaxies guide (faintfuzzies.com/Files/FlatGalaxies%20v2.pdf). With his 22-inch, Alvin described UGC 1817 as a "Very faint thin glow with ill-defined edges. Lower than expected surface brightness, goes to show how misleading the listed magnitude can be. But that is all we got when it comes to listed data. Practically disappears at 306x. PA = 150° and 1.6 long. Nearby galaxies, MCG+2-7-1, is very faint, round glow with ill-defined edges. Even surface brightness. About 0.2 across. A couple very faint 16th and 17th magnitude stars lies on the south and north edges respectively.
UGCA 114 is a chaotic barred spiral in Lepus, situated 5° south of 2nd-magnitude Saiph (Kappa), the star marking the southeast vertex of the main outline of Orion. At 200x I found a fairly faint and fairly large glow, slightly elongated, roughly 1.8' diameter but with an ill-defined outer edge to the halo. I only noticed a broad, weak concentration but without a well defined core or bar. The galaxy is bracketed by a mag 12.4 star 1.4' WNW of center and a mag 12.9 star 1.2' ESE of center. Using 282x, the diameter appeared 2'-2.5' with a mag 14.6 star on the west edge. The surface brightness was uneven with a slightly brighter central region. MCG -02-15-012 = PGC 17985, a tiny glow 5.6 SE was extremely faint and small, just 12"-15" diameter. The redshift of this galaxy is over 13x that of UGCA 114, so it lies far in the background.