May 1, 2011 Observing Report – A Taste of Discovery

Posted on May 19, 2011 by Denis

There is a long record of astronomical discoveries credited to amateur astronomers.  Some have been serendipitous, while others were the result of sustained effort.  I am an experienced observer, but have no astronomical discoveries to my credit.  Although I have no burning aspiration to add my name to the list of astronomers who have discovered something new, I do apply myself seriously to the craft of observing, making sure I am accurate in recording my observations and paying particular attention to that which I cannot readily explain.

I was able to take advantage of two clear nights at Zephyr Ridge Observatory on April 29 and 30, 2011, one week after my previous report of two nights of observing there.  The vast majority of objects observed during these four nights in April were galaxies and galaxy clusters.  My recent habit in planning my observing campaigns is to print a map for each object using Voyager software.  I structure the field of view of these maps to match the field of view of my widest field eyepiece, a 26mm Televue Nagler.  In this way I am able to verify that I am observing the object on my list, and the maps also show other nearby objects that may be visible.

On the night of April 30 at 11:57 PM, I observed the galaxy NGC3982 in Ursa Major (see below for the official log).  After completing this observation, I noticed a pair of nearby galaxies on my map, NGC3972 and NGC3977, and so I took the time to observe these as well.  When I examined NGC3972, I noticed a suspicious star just off the northern side of the halo near the center of the galaxy.  This star was not shown on my Voyager map, and so I mentioned it in my log, noting that it could be a possible supernova.  Of course, there are many other possible explanations, with map error being the most common.  I have been fooled before by similar instances; in fact, on the the previous night I saw a very bright star within the halo of NGC4866 in Virgo that was also not on my map, and was so intrigued I felt compelled to check into it an hour or so later, only to discover that it was just a bright foreground star.

As it happened, I did not check on the suspicious star in NGC3972 until about a week later, when I found to my surprise that it is a supernova, SN 2011by, originally discovered on April 26, four days before my sighting!  I found out about the discovery via the internet, and here is a site that shows it on a list of recent supernova discoveries:  http://www.supernovae.net/snimages/

Zhangwei Jin and Xing Gao are credited with the discovery of SN 2011by, and I offer my congratulations to them.  Meanwhile, I am proud that I found the supernova as well, if a few days late.  My discovery was entirely accidental, and confirms that making careful notes of one’s observations is an important habit to cultivate.  My lone mistake is that I did not look into the suspicious star until much later.  What if I had chanced to observe NGC3972 during my previous trip to Zephyr Ridge Observatory the week before?  I might have seen it then, and if I had waited to check into it, I would have missed a dream opportunity to receive credit for a supernova discovery.

Visual discoveries of extragalactic supernovae are rare, and to have a reasonable chance of discovering one, observers must have a systematic plan of observation and the dedication to persist night after night.  Most are found by imaging methods these days, and some amateur astronomers are conducting automated imaging programs for this purpose, one of the better known being the Puckett Observatory effort (http://www.cometwatch.com/search.html).  I have been unable to find a precise count of the number of supernovae that have been discovered by visual methods alone.  One possible count can be made from the list of awards given for such visual discoveries by the American Association of Variable Star Observers (http://www.aavso.org/novasupernova-award).  From this list, I counted a total of 60 visual supernova discoveries since 1928, of which the majority were credited to Robert O. Evans (http://en.wikipedia.org/wiki/Robert_Evans_(astronomer)) who is undoubtedly the most famous visual supernova hunter of them all.

Perhaps some day I will join the ranks of those who systematically pursue supernovae.  For now, I take personal pleasure in knowing that I independently discovered SN 2011by, even if four days after the first discovery.  It is highly improbable that I will accidentally discover a supernova again, but I will keep my eyes open.  I hope you will do the same.  After all, you cannot win a lottery without buying a ticket.

Denis


Observations

In the remainder of this post I offer my observing notes from this latest mission to Zephyr Ridge Observatory.  I had a clear sky on both nights, albeit slightly less transparent than the very best nights out there.  Unihedron Sky Quality Meter readings averaged 21.41 on April 29 and 21.37 on April 30.

Note:  The first four observations were made with my 4” Borg refractor.  The remainder were made using my 20” Obsession reflector.

4/29/2011  10:08 PM
NGC3621 Galaxy  Hya  Mag 9.7
RA 11h18m16s  Dec -32°48’42”  Size 10’x6.5’

I used the 4″ Borg for this observation because the south wall of my observatory obstructed the Obsession.  Very low altitude view (about 11 degrees).  At 53x this galaxy was visible with direct vision, although averted vision was helpful.  It appeared as a fairly large (for this magnification) elongated hazy glow.  There were two field stars superimposed on the south side of the halo, and with averted vision I detected another star superimposed on the north side of the halo.  I did not see any central brightening.

4/29/2011  10:10 PM
M83 NGC5236 Galaxy  Hya  Mag 8
RA 13h37m00s  Dec -29°52’04”  Size 13.1’x12.2’

At 53x with the 4″ Borg, this galaxy was brighter than the previous galaxy (NGC3621) and appeared to be a face-on spiral.  It was fairly large and circular, with a brighter core area and stellar nucleus.  I did not see spiral arms, but the halo did appear mottled.  There is a flat triangle of three stars at the edge of the south side of the halo, and a fainter fourth star next to the triangle.  Again, this was a very low altitude observation (9.5 degrees).

4/29/2011  10:19 PM
NGC2251 Open Cluster  Mon  Mag 7.3
RA 06h34m42s  Dec +08°22’00”  Size 10’

I verified the location of this cluster with a map.  Using the 4″ Borg at 53x, this cluster appeared as a modest-sized, elongated collection of stars.  I resolved at least 10 stars amidst a glow of starlight suggesting a larger unresolved population.  There are two brighter stars on one side of the cluster that may or may not be actual cluster members.  Note that the cluster was only 15 degrees above the horizon during this observation.

4/29/2011  10:30 PM
NGC2324 Open Cluster  Mon  Mag. 8.4
RA 07h04m12s  Mag +01°03’00”  Size 7’

This is a very faint cluster at 53x with the 4″ Borg (at less than 15 degrees altitude).  I used a map to find the precise location, aided also by a reference to a Y-shaped asterism of seven stars that sits nearby.  I found the Y asterism, and the cluster appeared next to it.  The cluster was a very dim hazy patch and I could resolve only two stars in the midst.  I attempted to increase the power, but by the time I installed the eyepiece and refocused, the cluster had dipped below the west wall of my observatory.

4/29/2011  10:55 PM
NGC3610 Galaxy  UMa  Mag 10.8
RA 11h18m25s  Dec +58°47’11”  Size 3.2’x2.5’

(Now using 20” Obsession.) At 363x this galaxy is fairly small but bright, with a slightly elongated halo and a small, bright core.  There is a field star to the SE just off the halo, and another a little further away to the west of the galaxy.

4/29/2011  11:06 PM
NGC3631 Galaxy  UMa  Mag 10.4
RA 11h21m03s  Dec +53°10’11”  Size 4.6’

At 363x this appeared to be a face-on spiral, with a circular halo that was obviously mottled, suggesting spiral structure even though I could not explicitly see spiral arms.  The core is bright and compact, and averted vision revealed a stellar nucleus.  A very nice galaxy.

4/29/2011  11:19 PM
NGC3665 Galaxy  UMa  Mag. 11.6
RA 11h24m44s  Dec +38°45’45”  Size 3.2’x2.6’

Although the wind had picked up and jostled my scope, I was able to make a reasonable observation at 363x.  NGC3665 has a bright core and stellar nucleus.  The moderate-sized halo is slightly elongated.  A faint field star sits north of the halo.  There is a companion galaxy, NGC 3658, located to the SW, which required that I slew a short distance to see.  This galaxy is smaller and not quite as bright.  It has a prominent stellar nucleus and a circular halo.  Three bright field stars surrounded the galaxy in an approximate equilateral triangle.

4/29/2011  11:32 PM
NGC3675 Galaxy  UMa  Mag. 11
RA 11h26m08s  Dec +43°35’09”  Size 5.9’

The wind continues to buffet my scope.  At 363x this is a fine galaxy.  It is large, and has a substantially elongated halo – a nearly edge-on spiral – and the core is also elongated and had a lumpy appearance.  The halo is oriented N-S, and the east side of the halo appeared to be pinched-in, suggesting a possible dust lane.  Two field stars bracket the halo just off the southern tip, one west and one east.  Beautiful galaxy.

4/29/2011  11:42 PM
NGC3813 Galaxy  UMa  Mag 11.7
RA 11h41m18s  Dec +36°32’47”  Size 2.3’x1.2’

At 363x this galaxy appeared as an oval haze with gradual brightening towards the center.  I suspect an elongated core, but am not certain.  There is a nearby field star off the eastern tip.  Another pair was seen off the western tip.  There is also a field star just south, and another to the NNE that was a little further away.

4/29/2011  11:54 PM
NGC3877 Galaxy  UMa  Mag 12
RA 11h46m08s  Dec +47°29’41”  Size 5.4’

At 363x, this is another fine edge-on spiral.  It had a large elongated halo that appeared mottled.  The core was fairly small and averted vision revealed a stellar nucleus.  There is a bright equilateral triangle of stars NNE of the galaxy and the halo protrudes towards the center of the triangle.  Nice.

4/30/2011  12:08 AM
NGC4665 Galaxy  Vir  Mag 12.4
RA 12h45m06s  Dec +03°03’20”  Size 4.2’x3.5’

Observed at 363x.  This galaxy had a slightly elongated halo and a bright core.  I intermittently glimpsed a stellar pinpoint in the center.  There is a bright nearby field star just SW of the halo, and another bright one to the NE.  Two faint stars nearly overlap the halo on the NW.

4/30/2011 12:16 AM
NGC4697 Galaxy  Vir  Mag 9.3
RA 12h48m36s  Dec -05°48’02”  Size 6’x3.8’

At 363x, this is another fine Virgo galaxy.  It is quite bright, with a bright and slightly elongated core.  The slightly elongated halo was a diffuse glow that dissipated gradually into the background so that the boundary was uncertain.  There is nearby field star just NNW of the core.  Another is ENE of the core.

4/30/2011 12:25 AM
NGC4699 Galaxy  Vir  Mag 9.6
RA 12h49m02s  Dec -08°39’52”  Size 3.5’x2.7’

At 363x, this is a nice bright galaxy with a tiny, nearly stellar core and a small halo that was slightly elongated.  There are three nearby field stars, a faint one to the south and two to the east, the further eastward star being the brightest.

4/30/2011 12:31 AM
NGC4753 Galaxy  Vir  Mag. 9.9
RA 12h52m22s  Dec -01°11’58”  Size 5.4’x2.9’

At 363x, this galaxy is a moderately large oval, with a small core and nearly stellar nucleus.  There is a little mottling in the halo near the core, and moving away from the core the halo gradually faded into the background.  There is a field star to the west just off the halo.  A pair of stars was also seen to the NE of the galaxy.

4/30/2011 12:37 AM
NGC4781 Galaxy  Vir  Mag 12.8
RA 12h54m24s  Dec -10°32’12”  Size 3.5’x1.8’

Observed at 363x.  This galaxy is a moderate-sized elongated cloud with an irregular border.  I saw no central brightening.  There are two nearby field stars to the west, one overlapping the halo and one just off the halo, and a third field star was further away to the west.  To the SE there is a small companion galaxy, NGC4784, which had a rather small, elongated halo and a brighter core with a stellar nucleus.  NGC4784 sits in between two bright stars, one to the west and one to the north.  Returning to NGC4781 and slewing westward, I found NGC4760, which lies between two bright stars, one NE and one SW.  NGC4760, while not particularly bright, exhibited mild halo elongation and core brightening.

4/30/2011  12:48 AM
NGC4845 Galaxy  Vir  Mag 12.9
RA 12h58m01s  Dec +01°34’34”  5’x1.6’

At 363x, this galaxy is quite elongated, with a mottled halo.  There is only a little brightening of the core.  Averted vision revealed two stellar pinpoints within the galaxy, one centered in the core and one east of the core.  There is a pair of field stars just south of the halo and another star sits just north of the eastern side of the halo.

4/30/2011  12:56 AM
NGC4866 Galaxy  Vir  Mag 11.2
RA 12h59m27s  Dec +14°10’14”  Size 6.5’x1.5’

At 363x, this galaxy was very interesting.  It is an edge-on spiral with a compact core and stellar nucleus.  The halo is thin and of moderate length.  There is a bright star overlapping the halo to the west of the core, perhaps 2/3 of the way from core to western tip.  The star sits a little north of the halo’s primary axis.  This star is not shown on my map, and so I immediately wondered whether this could be a supernova.  But – alas! – later research showed the star in many photographs found online.

4/30/2011  1:05 AM
NGC4900 Galaxy  Vir  Mag 11.5
RA 13h00m39s  Dec +02°30’06”  Size 2.3’x2.2’

363x.  A moderate-sized, roughly circular cloud.  It had a tiny core that was only slightly brighter than the halo, and a stellar pinpoint was evident in the center using averted vision.  A bright field star is superimposed on the south edge of the halo.

4/30/2011  1:16 AM
NGC4958 Galaxy  Vir  Mag 10.5
RA 13h05m49s  Dec -08°01’14”  Size 4.1’x1.4’

363x.  A rather small elongated streak.  There is a bright core that was slightly elongated along the major axis.  There is a field star just to the west of the galaxy.  There is a companion galaxy, NGC4948, to the WNW and just outside the field of view with this eyepiece.  I slewed to it, and it appeared much fainter than the main galaxy, with an elongated halo and no brightening in the core area.  A pair of field stars sits to the south, just off the tip of the halo.

4/30/2011  1:22 AM
NGC4995 Galaxy  Vir  Mag 11
RA 13h09m41s  Dec -07°50’01”  Size 2.5’x1.7’

At 363x, this galaxy is a ghostly glow.  The halo is slightly elongated, and averted vision revealed a stellar nucleus without much accompanying central brightening.  There is a very bright field star just to the north of the galaxy, and a much fainter star just east of the bright star.

4/30/2011  1:30 AM
NGC5054 Galaxy  Vir  Mag 11.7
RA 13h16m58s  Dec -16°38’07”  Size 5’x3.1’

363x.  This galaxy was at low altitude and I may have been partially obstructed on the SW corner of the building.  The galaxy appeared quite dim, and seemed to be a nearly face-on spiral.  The halo is slightly elongated and mottled.  There is some central brightening in the core area, but it was subtle.  Two field stars are just off the NW edge of the halo, and two other field stars sit just east of the core and possibly overlapping the halo.  My map shows a faint companion galaxy overlapping the north edge of the halo, but I did not see it.

4/30/2011  1:39 AM
NGC5248 Galaxy  Boo  Mag 10.2
RA 13h37m32s  Dec +08°53’08”  Size 6.5’

363x. This is a nice galaxy.  It has a fairly large oval-shaped halo, with a moderately bright core that seemed a little elongated.  There is a field star within the halo NNE of the core.  The halo is mottled and suggested spiral structure, although I could not explicitly trace arms.  There is another field star just off the halo to the SSW.

4/30/2011  1:45 AM
NGC5897 Globular Cluster  Lib  Mag 9.5
RA 15h17m24s  Dec -21°00’37”  Size 11.0′

At 212x, this appeared as a fairly large, loosely organized globular cluster.  Unlike most globulars, this cluster does not have a focused core region. There is an overall large region of unresolved haziness suggesting a rich collection of stars.  I could resolve about 25 stars, approximately.  Without the expected central concentration, I would expect this cluster to have a high value for the concentration class.  I estimate 10 or 11.  (Note:  Uranometria 2000, Vol. 3, gives a value of 11.)

4/30/2011  10:37 PM
NGC3158 Group Galaxy Cluster  LMi  Mag 11.8
RA 10h13m51s  Dec +38°45’53”  Size 2.3

A little breezy, and the sky transparency seems only so-so – clear, but I have seen better nights here.  Lots of afternoon clouds may have left some moisture content.  I used a map to confirm this group and aid in the tour, performed at 363x magnification.  NGC3158 is fairly small with a bright core and small, nearly circular halo.  Moving WSW, there is a field star, and just north of the field star I saw a very faint fuzzy spot, which I identified as galaxy PGC2135428.  Extremely faint, but visible.  Returning to the main galaxy and moving directly north, there is a faint streak located just north of a field star.  This is NGC3160; it appeared as just a faint elongated streak with no apparent central brightening.  Moving west from this galaxy, I was able to detect another very faint smudge that only appeared nonstellar with averted vision.  This is NGC3152 – another extremely faint galaxy that is only barely visible and is very small; there is a field star just ENE of this fuzzy spot.  Returning to the main galaxy, I now slewed southward towards another local grouping.  I found a row of three galaxies with a field star just south of the center of the row.  The row is oriented E-W.  The westernmost galaxy, NGC3159, appeared as a small fuzzy glow that had brightening in the core.  The halo looked roughly circular.  The center galaxy, NGC3161, was a smaller circular glow with just a hint of core brightening.  The easternmost galaxy in the row, NGC3163, also appeared circular and had a stellar nucleus.  Now, I slewed slightly west of this row of three and encountered a pair of field stars whose connecting line is oriented WSW-ESE.  In between these two stars, I saw two very faint galaxies oriented roughly N-S, NGC3150 and NGC3151.  Both were barely discernable, although the southernmost, NGC3151 had some visible core brightening.  Just to the east of NGC3151, I also saw a very faint point of light that had a little fuzziness around it, which I identified as PGC2131950, an extremely faint galaxy.  This concludes my survey of this galaxy cluster.

4/30/2011  10:50 PM
Hickson 46 Galaxy Cluster  Leo  Mag 12.3
RA 10h22m02s  Dec +17°48’54”  Size 3.6’

Observed at 363x and the location was precisely determined with reference to a detailed map from Voyager software.  This grouping is at the limit of my instrument and eyes this evening.  I was able to see a row of three hazy spots, best seen by gently slewing the telescope and using averted vision.  I could see that the central member was larger than the outer two.  My map shows there are two galaxies at this central location, but I could not distinguish the two, and evidently could only see the combined light from both merged into one larger glow.  A difficult group.

4/30/2011  10:57 PM
Markarian 421 Galaxy/BL Lacertae Object  UMa  Mag 13.4
RA 11h04m27s  Dec +38°12’23”  Size 0.3’x0.23’

This blazar (blazing quasi-stellar object) is a BL Lacertae object located approximately 400 million light years away.   At 363x it was easy to find because it is located right next to two very bright stars, the brightest being 51 Ursa Majoris (mag. 6).  Markarian 421 appeared as a moderately faint field star in the presence of the glare from the two bright stellar neighbors.  I slewed the scope so that the field stars were outside of the field of view, and then Markarian 421 appeared a tiny bit fuzzy.  However, I am not certain whether this is due to my being able to see its true nature or if this fuzziness was an optical artifact from having the object so close to the edge of the field.  In any case, the blazar is certainly visible.

4/30/2011  11:09 PM
NGC3801 Group Galaxy Cluster  Leo  Mag. 12.1
RA 11h40m17s  Dec +17°43’40”  Size 3.2’

Observed at 363x.  I was able to see most of the members of this group.  The main galaxy, NGC3801, has a moderate-sized and slightly elongated halo with mild brightening in the core.  Just to the south, I saw NGC3802, an elongated streak, with the eastern tip pointing to a field star.  Moving further north, I saw an extremely faint and elusive glow that required slewing the scope and using averted vision, which I identified as NGC3803.  Continuing north and a little west, there is a pair of field stars, and proceeding further to the WNW from this pair, I was able to detect another extremely faint glow, again requiring averted vision and gently slewing the telescope to see at all; I identified this galaxy as PGC36178.  Returning to the main galaxy and slewing westward, there is a triangular asterism of three stars, and to the WNW of the brightest star in this group I saw a small galaxy with an elongated halo and a stellar nucleus.  My map shows the galaxy PGC36189 near the southernmost member of the star triangle, but I was unable to see it.  Returning to the main galaxy and slewing to the east, there is another triangular asterism of three stars, the southernmost member being quite bright.  Moving north from this asterism, I saw another extremely faint galaxy, which is barely visible with direct vision once detected.  This is NGC3807, and it appeared as a hazy spot that was a little larger than the other members of this group, with the exception of the main galaxy, NGC3801.

4/30/2011  11:22 PM
NGC3938 Galaxy  UMa  Mag 10.4
RA 11h52m49s  Dec +44°07’13”  Size 5.4’x4.9’

At 363x, this galaxy is obviously a face-on spiral.  Overall it is not particularly bright, but is easy to see.  The circular halo was mottled and had an irregular border, and there was a hint of spiral structure even though I could not clearly trace arms.  The core region was brighter and occasionally I glimpsed a stellar pinpoint in the center.  There is a field star to the SE of the galaxy.

4/30/2011  11:29 PM
NGC3941 Galaxy  UMa  Mag 11.3
RA 11h52m55s  Dec +36°59’10”  Size 3.8’x2.5’

At 363x, this galaxy had a very bright, elongated core (oval-shape).  Averted vision improved the extension of the core, making the oval even more apparent.  The halo is fairly small and also elongated.  There is a field star just off the halo to the east.

4/30/2011  11:34 PM
NGC3949 Galaxy  UMa  Mag 11
RA 11h53m42s  Dec +47°51’29”  Size 3’x1.8’

Observed at 363x.  This galaxy has an oval-shaped halo and is moderately bright.  It had only slight brightening in the core that resolves to a stellar pinpoint in the center.  Just outside the core area I saw a little mottling, suggesting dark regions in the halo right next to the core.

4/30/2011  11:45 PM
NGC3953 Galaxy  UMa  Mag 10.1
RA 11h53m49s  Dec +52°19’36”  Size 6.6’

Nice!  At 363x, this is a fairly large galaxy with an elongated halo and a bright core that was a bit elongated. Careful inspection revealed that the main axis of the core is slightly off-axis relative to the halo.  The halo is a little mottled, especially in the vicinity of the core. There are two field stars overlapping the halo near the core.  One is roughly NNE of the core, and the other is roughly west of the core.

4/30/2011  11:57 PM
NGC3982 Galaxy  UMa  Mag 11.7
RA 11h56m28s  Dec +55°07’29”  Size 2.5’x2.2’

At 363x, NGC3982 appeared as a small, roughly circular cloud with a stellar nucleus.  I saw some mottling near the core, suggesting that this could be a small face-on spiral.  There is a fairly bright pair of field stars to the south of the galaxy.  This galaxy has a couple of nearby companions to the north (requiring me to slew the scope a short distance), which fit comfortably together in the field of view of this eyepiece.  The southernmost member, NGC3972, is a fairly large elongated streak with no apparent central brightening.  There is a rather bright field star just off the center of the halo roughly to the north (in the direction of the companion galaxy) which is not shown on my map (makes me wonder – possible supernova?).  The companion galaxy, NGC3977, is a rather faint, roughly circular hazy ball with gradual and subtle brightening towards the core.

Note:  On 5/9/11 I searched online concerning NGC3972 and found that the mysterious field star just off the center of the halo to the north is indeed a supernova, discovered on April 26, 2011!  It is designated PSN J11554556+5519338 on the IAU Central Bureau for Astronomical Telegrams (http://www.cbat.eps.harvard.edu/unconf/tocp.html) and has been designated SN 2011by, as reported in the AAVSO Alert Notice 438. ( http://www.aavso.org/aavso-alert-notice-438).

5/1/2011  12:14 AM
NGC4026 Galaxy  UMa  Mag 12
RA 11h59m25s  Dec+50°57’42”  Size 5.1’

Observed at 363x.  This is a nice edge-on spiral with a bright, compact core and an extended thin halo that responded well to averted vision, which increased the extension.  There are some attractive nearby field stars. The closest is just east of the southern tip of the halo.  Some brighter stars are further south from there.  There is another field star just east of the northern tip of the halo.

5/1/2011  12:24 AM
NGC4036 Galaxy  UMa  Mag 10.6
RA 12h01m27s  Dec +61°53’44”  Size 4.5’

At 363x, this is another nice edge-on spiral with a bright core and stellar nucleus.  The halo was moderate-sized, but did not extend quite as far as the previous galaxy I observed (NGC4026).  After careful study, I suspect a possible dust lane on the south edge along the main axis, where it looked a little pinched-in, especially near the core.  It’s subtle, and so I am not certain of this assessment.

5/1/2011  12:29 AM
NGC4041 Galaxy  UMa  Mag 11.2
RA 12h02m12s  Dec +62°08’15”  Size 2.8’x2.7’

Observed at 363x.  This galaxy is located just NNE of NGC4036, observed just before.  NGC4041 has a small, circular halo that diffuses gradually into the background.  There is gradual brightening towards the core and I would assess the core as rather large.  There is a field star off the halo to the NE.

5/1/2011  12:41 AM
NGC4102 Galaxy  UMa  Mag 11.8
RA 12h06m23s  Dec +52°42’39”  Size 3.2’x1.9’

At 363x, this is an interesting galaxy.  It is of modest size and had an oval-shaped core with a stellar nucleus.  The halo is also elongated, and the long axis is oriented SW to NE.  The SW side of the halo seemed more disturbed, especially more towards the south.  It seemed more mottled/broken-up in that direction.  On the SW edge of the halo there is a bright field star.  Just off the NE end is another field star, which is not quite as bright and a little further away from the galaxy.

5/1/2011  12:48 AM
NGC4005 Galaxy Cluster  Leo  Mag 14
RA 11h58m10s  Dec +25°07’19”

I toured this group at 363x.  This group is anchored by a very bright star (HD103913, mag. 8.27), and the main galaxy, NGC4005, is SE of that star and immediately south of a much fainter field star.  NGC4005 is not particularly bright, although easy to see, with an oval halo and mild central brightening.  Returning to the bright star and moving westward, I saw NGC4000, which is a very faint elongated streak.  Now I slewed back to the SE to located NGC4011 (ESE of NGC4005 by my map), but after careful inspection, I was unable to see it (Voyager software gives it mag. 15.75).  So, I slewed past these, continuing SE and found NGC4015 and NGC4023.  NGC4015 is faint, although conspicuous, with a roughly circular halo, and mild core brightening with a stellar nucleus.  NGC4023 is smaller and elongated, with no central brightening.  At this point exhaustion and irritability stopped my progress, as I was perched in an awkward position on the ladder and my controlling hand was getting frozen!  So, I stopped here, even though other galaxies remained according to my map.

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April 23, 2011 Observing Report

Posted on May 2, 2011 by Denis

I enjoyed two clear nights at Zephyr Ridge Observatory (ZRO) on April 21-22, and in this post I will discuss my observations.

I recently purchased a Unihedron Sky Quality Meter (http://unihedron.com/projects/darksky/), a device that measures sky brightness.  I measured the sky brightness at ZRO several times during each night, and intend to continue taking and tracking these measurements.

For those who are unfamiliar with the idea of measuring sky brightness, I suggest reading this excellent article by Brian Skiff:  http://www.astropix.com/HTML/L_STORY/SKYBRITE.HTM According to Mr. Skiff, a sky that is completely free of man-made light pollution would obtain a sky brightness reading of 22 mag/arcsec2.  He also suggests that a “true-dark” site is one that achieves a reading of 21.5 mag/arcsec2 or higher.

On April 21, I visually judged the sky to be decent, but perhaps a notch below the best I have experienced at ZRO.  The average meter reading I recorded that night was 21.40 mag/arcsec2.  This is the average of nine measurements taken over the course of the night, all taken with the meter pointed to the zenith.  I excluded three readings taken just after the 77% gibbous moon had risen; these readings averaged 20.78 at zenith, showing the deleterious effect the moon has on the sky even when at the horizon.

On the next night the sky looked better visually, and I judged it to be on par with the better nights I have experienced at ZRO.  I was pleased that meter agreed with my assessment, this time achieving an average of 21.53 mag/arcsec2.  I will continue to report my experiences with this device in future posts.

On to my observations!  The majority of my observations were of galaxies and galaxy clusters.  With my 20” Obsession, I am able to enjoy the varieties of shapes and features that are often invisible in smaller instruments, and I endeavor to carefully record these nuances.  I provide a list below, but would like to call attention to some notable objects.

First, I recommend NGC4038/4039 in Corvus, the so-called Antennae Galaxies.  These galaxies should be visible in smaller instruments, and it is well worth the effort.  This is an impressive interacting pair of galaxies, although I did not actually see the long filaments that account for the name.

Another bipolar gem is the Planetary Nebula NGC2371 (or NGC2372) in Gemini, also bright and suitable for smaller instruments.  I had observed this before, but not at ZRO, and so treated myself to another view of this fine object.  Catch it while you can, as Gemini is receding in the western sky.  By the way, NGC4361 in Corvus is another excellent Planetary Nebula.

Lastly, I successfully observed the Proto-Planetary Nebula known as Frosty Leo.  Here is a link to a nice article about such objects:  http://www.schoenball.de/astronomie/projekte/ppn/ppn_en.htm Frosty Leo is considered a challenging visual object, but with my 20” Obsession and dark sky I was able to see it without difficulty.

I would be interested to hear from readers about your experiences with these or other objects in the April (and May) sky.  April is “galaxy month” in the northern hemisphere, as there are many fine galaxies in prime position.  I hope you have seen or will see some of these distant “island universes.”

Denis

4/21/11  10:15 PM
NGC2371/2372 Planetary Nebula  Gem  Mag 13
RA 07h25m35s  Dec +29°29’36”  Size 1.23’x0.9’

Calming wind and clear, but some moisture content in the air reduced my transparency rating one point below “perfect.”  At 363x this PN is clearly bipolar.  The SW lobe seemed to have a condensed core region – like the core of a galaxy – and this made it a little brighter than the NE lobe, which appeared more diffuse.  In between the lobes I could see the central star.  Averted vision revealed it, and once I was able to see it with direct vision after spotting it with averted vision.  There is a smattering of stars nearby.  An apparent double star appears on the north side of the nebula.  Very nice object.

4/21/11  10:25 PM
NGC2811 Galaxy  Hya  Mag 11.3
RA 09h16m11s  Dec -16°18’47”  Size 2.7’x1’

Possible partial obstruction with wall on SW corner.  At 212x this galaxy appeared to be an oblique or edge-on spiral. It is fairly small and has a bright and tightly condensed nonstellar core that yields abruptly to a diffuse elongated halo.  There is a bright star just to the west of the core.  There is a faint star – seen more easily with averted vision but sometimes also directly – just off the halo on the NE side of the galaxy.

4/21/11  10:33 PM
NGC3962 Galaxy  Crt  Mag 10.6
RA 11h54m40s  Dec -13°58’31”  Size 2.9’x2.6’

At 212x this is a small, fairly bright fuzzy.  It has a bright nonstellar core, and direct vision showed a rather small halo.  With averted vision, the extent of the halo was much greater, although the glow was rather subtle.  The halo was slightly elongated.  There is an arc of 4 stars that places a bound on the south side of the galaxy; the two western stars of the arc are bright and the two eastern stars are fainter.

4/21/11  10:48 PM
NGC4027 Galaxy  Crv  Mag 11.1
RA 11h59m31s  Dec -19°15’59”  Size 3’x2.3’

At 212x this is a large and diffuse galaxy, with a roughly circular halo that gradually brightened towards the center.  The halo is rather large, and there is a faint field star overlapping the halo on the east side, and another faint star just off the halo to the west.  A bright pair of stars appeared to the north.  I did not see the companion NGC4027A.

4/21/11  10:55 PM
NGC4038/4039 Galaxies  Crv  Mag 10.7
RA 12h01m53s  Dec -18°51’54”  Size 3.4’x2’

Very interesting.  At 212x this quite clearly looked like two interacting galaxies.  The initial impression is of a V-shaped region of nebulosity, or, put another way, two intersecting lobes separated by a dark area in between, with the intersection occurring at the ends of the lobes at an angle.  The two lobes seemed to be elongated and mottled with no obvious central brightening.  The northernmost lobe, NGC4038, is shorter and wider, and the stellar material seemed denser. The southernmost galaxy, NGC4039, is longer and thinner.  With averted vision I could pick up stellar pinpoints towards the center of each lobe.  There is a star just off the halo of NGC4038 to the north.  I did not see the antennae protrusions visible in photographs.

4/21/11  11:08 PM
NGC4361 Planetary Nebula  Crv  Mag 10.9
RA 12h24m31s  Dec -18°47’05”  Size 1.9’

Quite nice.  At 212x this appeared as a moderate-sized gray disk, roughly circular with a mottled appearance.  The central star is obvious.  Using an OIII filter, the blotchy/mottled appearance was accentuated and the object now seemed a little elongated.  One of the better PNs.

4/21/11  11:31 PM
IRAS 09371+1212 Frosty Leo Planetary Nebula  Leo  Mag 10.5
RA 09h39m54s  Dec +11°59’00”  Size 12″

At 212x this nebula was easy to spot just to the east of a field star, and I confirmed the location with a map.  It was a faint, small glow visible with direct vision.  At 363x I was able to see a slight bit of elongation, but the wind had picked up during this observation and the seeing may have degraded, as I preferred the view at 212x.  Central star was not visible.  I did not see lobes or other structure; perhaps on a better night?  Inserting an OIII did not help; in fact, I was unable to see anything at all.

4/21/11  11:44 PM
NGC2654 Galaxy  UMa  Mag 11.8
RA 08h49m12s  Dec +60°13’14”  Size 4.3’

At 363x, a nice elongated streak.  Clearly an edge-on spiral.  Fairly large, with a bright elongated core.  I could glimpse a stellar pinpoint nucleus with averted vision.  The extended halo was fairly bright and easy to see.  There are nearby field stars, most of which were near the SSE side of the galaxy.

4/21/11  11:55 PM
NGC2681 Galaxy  UMa  Mag 10.3
RA 08h53m33s  Dec+51°18’49”  Size 3.8’

At 363x this galaxy is quite bright, with a bright, small core and stellar nucleus.  The halo is roughly circular and offers a fainter contrast to the bright core.  There is a very bright star to the SE of the galaxy, just outside the field of view.  Within the field, there is a pair of bright stars roughly west of the galaxy, with another bright star north of the pair.  Approximately east of the galaxy there is a wider pair of bright stars.

4/22/11  12:04 AM
NGC2787 Galaxy  UMa  Mag 10.8
RA 09h19m19s  Dec +69°12’11”  Size 3.4’

At 363x this galaxy is fairly bright, with a large, elongated core and an elongated halo.  I noticed a possible field star within the halo, and another star just off the halo to the SE.  Also, there were two field stars roughly west of the halo and another to the NW.

4/22/11  12:17 AM
NGC2841 Galaxy  UMa  Mag 9.3
RA 09h22m03s  Dec +50°58’35”  Size 8.1’

A fine object.  At 363x it appears as an oblique spiral, with a large bright core.  The halo is also large, and on the NE side of the galaxy the halo seemed a little pinched in as compared to the SW side of the galaxy, and so I suspect a possible dust lane on the NE side.  (There is also a bright star off the NE side of the galaxy.)  There are bright stars towards the NW tip of the galaxy – three bright ones and one fainter one – and one of these four stars appears contained with the halo.

4/22/11  12:28 AM
NGC2859 Galaxy  LMi  Mag 10.7
RA 09h24m19s  Dec +34°30’49”  Size 4.8’x4.2’

At 363x this galaxy has a bright nonstellar core with an approximately circular halo.  On first impression the halo seemed small, but with patience and averted vision I could see more extension.  Photos show an inner halo and a separate outer ring; I did not see this separation, but I speculate that perhaps with averted vision I was picking up some of this outer ring.  My map showed a superimposed field star on the northern side of the halo, but I did not see it.  There is a bright field star off the WNW side of the galaxy.

4/22/11  12:38 AM
NGC4179 Galaxy  Vir  Mag 10.9
RA 12h12m52s  Dec +01°18’01”  Size 4.2’x1.2’

At 363x this galaxy was a nice elongated streak. The core was bright and had a stellar nucleus.  The halo was rather small.  There is a field star on the NW tip that is clearly embedded within the halo.  There are also field stars NE of the center of the galaxy – a pair of faint ones close in and a wider pair of brighter stars further out on this side.

4/22/11  12:46 AM
NGC4273 (and others) Galaxy  Vir  Mag 11.9
RA 12h19m56s  Dec +05°20’38”  2.3’x1.5’

This galaxy is located in a nice field of several other galaxies, and I used a map to navigate among these.  At 363x, NGC4273 appeared fairly large with a somewhat elongated halo with only slight brightening towards the center.  I saw a stellar pinpoint near the center; whether this was the nucleus or a field star is uncertain.  Just off the halo to the east I saw a faint smudge that is just north of a field star, which I identified as NGC4277.  Returning to NGC4273 and moving SSW, I saw NGC4268, which was easy to see, with a bright core and elongated halo.  There is a nearby field star to the NW of this galaxy.  Returning to NGC4273 and slewing roughly ENE, I found NGC4281, which was bright with an elongated core, stellar nucleus and elongated halo – looked like an edge-on spiral.  Returning to NGC4273 and slewing north from there, I found NGC4270, which appeared as another elongated halo with a slightly brighter core and stellar nucleus.  Moving further north there are a pair of very bright stars, and just south of the westernmost member of this pair I was able to pick up (with averted vision) a very faint elongated fuzzy, which I identified at NGC4266.  There are even more galaxies I could have hunted in this field, but I decided to stop here.

4/22/11  12:59 AM
NGC4527 Galaxy  Vir  Mag 10.4
RA 12h34m09s  Dec +02°39’11”  Size 6.3’x2.3’

The moon has now risen in the eastern sky.  At 363x this galaxy is elongated and has a brighter core area and with averted vision I glimpsed a stellar nucleus.  The halo had a filmy appearance that gradually diffused into the background.  There is a field star roughly west of the galaxy.

4/22/11  1:04 AM
NGC4536 Galaxy  Vir  Mag 10.4
RA 12h34m27s  Dec +02°11’15”  Size 7.4’x3.5’

I confirmed the location of this galaxy with a map.  At 363x this galaxy appeared as a large hazy glow – rather faint – with no real brightening towards the core.  I did see a stellar nucleus.

Next night:

4/22/11  9:52 PM
NGC2373/2375/2379 Galaxy Cluster  Gem  Mag 14
RA 07h26m37s  Dec +33°49’26”

Very good conditions this evening.  Excellent transparency and good seeing.  At 363x, these galaxies do not quite fit into the field of view.  The smallest of the group is NGC2373, which appeared as a tiny fuzzy spot just to the SW of a fairly bright field star.  Moving eastward and directly south of another field star, I found NGC 2375 which appeared as a larger cloudy haze that did not seem elongated, nor did it have any apparent central brightening.  Moving ESE and arriving just ESE of a relatively bright star is NGC2379, which is another fairly large, circular cloud, but this one had a stellar nucleus.

4/22/11  10:04 PM
NGC2385/2388/2389 Galaxy Cluster Gem  Mag 15
RA 07h28m28s   Dec +33°50’16”

At 363x, the westernmost galaxy is NGC2385, which is located in a lonely area and is quite faint.  I could barely see it with direct vision; averted vision improved the view, but in either case it was a very small faint hazy spot.  Moving to the east, the next galaxy is NGC2388, located SW of a field star.  This is also a faint galaxy, although a little larger and brighter than the previous member, and with a slightly elongated halo.  The last galaxy, NGC2389, is directly south of a fairly bright star, and is of similar brightness overall to the previous galaxy (at least in the halo), but this one had a little bit of core brightening.  Averted vision revealed a slightly elongated halo.

4/22/11  10:36 PM
NGC2872/2873/2874 Galaxy Cluster  Leo  Mag 13
RA 09h25m43s  Dec +11°25’56”

Observed at 363x.  This is a very tight grouping, and I was only able to see two main members, and my map showed all three so close together that I was unclear as to the identities of what I saw.  I saw two fuzzy areas.  One had a bright compact core and a slightly elongated halo.  The second was larger and more elongated, with core brightening – although less bright than the first – and averted vision revealed a stellar nucleus.  I could not distinguish a third galaxy, so it was either too faint, or overlapped the first two.

4/22/11  10:52 PM
NGC2943 Group Galaxy Cluster  Leo  Mag 14
RA 09h38m33s  Dec +17°01’53”

I toured this group at 363x.  The main galaxy, NGC2943, is SW of an apparent double star, although my map shows it as a star with a galaxy next to it.  NGC2943 is a fairly large, slightly elongated glow with a brighter core area.  Just to the west of this galaxy is NGC2941, which is more difficult to see, but was visible as a small, dim fuzzy spot with little central brightening and a slightly elongated halo.  Moving westward, I found NGC2933 located just north of a pair of stars, one of which is quite bright.  NGC2933 is very faint and quite elongated, a thin spindle.  Moving further west, I found NGC2928, which is also very faint – almost invisible – and averted vision revealed some elongation and no apparent central brightening.  Returning to NGC2943 and slewing eastward, I found NGC2946, which is just north of a row of 3 N-S stars.  This galaxy was also extremely faint, with a tiny bit of central brightening yielding to a dim, diffuse halo that seemed a little elongated.  Next I slewed to the SE to find NGC2949, and despite using a map to pinpoint the location, it was too faint to see.  So, I ended this tour with five confirmed galaxies.

4/22/11  11:15 PM
NGC2950 Galaxy  UMa  Mag 11
RA 09h42m35s  Dec +58°51’04”  Size 3.2’x2.1’

At 363x this modest-sized galaxy was bright, with a bright, tight core and a nearly stellar nucleus.  The halo was relatively small and slightly elongated.  There is a bright star to the west of the galaxy, and between this star and the galaxy, just off the halo, there is an arc of three much fainter stars.

4/22/11  11:28 PM
NGC3003 Galaxy  LMi  Mag 11.7
RA 09h48m36s  Dec +33°25’17”  Size 5.9’

At 363x this galaxy is fairly large and quite elongated; it seemed to be a nearly edge-on spiral.  The central core area was only slightly brighter than the halo and was also elongated.  The halo seemed to have an irregular shape, and the eastern side seemed wider or more bulged-out than the western side.  Near the western edge of the halo, I was able to detect with averted vision a faint field star superimposed on the halo.  Also, to the west of the halo, I saw a curving arc of four stars.

4/22/11  11:38 PM
NGC3184 Galaxy  UMa  Mag 9.8
RA 10h18m17s  Dec +41°25’27”  Size 6.9’

At 363x this appeared to be a large, face-on spiral.  The galaxy seemed to have low surface brightness overall, but I could discern some of the spiral structure.  I could make out most of one outer arm, which circled around the west side and ended towards the north edge, where there is a bright field star that overlapped the end of the arm.  I was unable to trace another arm completely, but the rest of the halo exhibited a broken character, with knots, gaps and a swirling character that suggested spiral structure.  The nonstellar core was only a little brighter than the halo.

4/22/11  11:50 PM
NGC3198 Galaxy  UMa  Mag 10.4
RA 10h19m55s  Dec +45°33’00”  Size 8.3’

Observed at 363x.  This galaxy is substantially elongated, with an irregular perimeter to the halo.  The core is fairly large and only slightly brighter than the halo.  The halo was mottled and the two tips of the halo did not taper smoothly, but had a ragged appearance.  The SE portion of the halo seemed to bulge out more than the opposite end.  Just to the north of the galaxy there is a bright star.  A pair of fainter stars appeared to the SE.

4/23/11  12:02 AM
NGC3310 Galaxy  UMa  Mag 11.1
RA 10h38m46s  Dec +53°30’12”  Size 3.6’x3’

At 363x this galaxy gave a peculiar impression.  There is a dominant core, which was large, bright and circular and also exhibited mottling.  The halo protrudes only a small distance outward from the core.  The impression I got was of two objects superimposed, as if there was a bright blob superimposed on something larger and fainter.  There are a few field stars north of galaxy, one faint one nearby, then a brighter one, and a few others further away from the galaxy.

4/23/11  12:10 AM
NGC3486 Galaxy  LMi  Mag 10.3
RA 11h00m24s  Dec +28°58’32”  6.9’x5.4’

Observed at 363x.  Nice.  This galaxy had a mottled core surrounding a stellar nucleus.  The fainter halo dissipated gradually into the background, and averted vision revealed more extension than the initial direct vision impression.  Careful examination suggested slight elongation to the halo, a mild oval shape.

4/23/11  12:30 AM
NGC4365 (and others) Galaxy  Vir  Mag 11.5
RA 12h24m28s  Dec +07°19’04”  Size 6.2’x4.6’

At 363x, NGC4365 had a bright concentrated core and a moderate-sized halo which was slightly elongated.  There are several other galaxies nearby.  Slewing NE, I found NGC4366 which is a very faint haze.  Moving further NE, I found NGC4370, which was a bit brighter, with an elongated halo and somewhat brighter core.  Two bright stars were located SE, and there is supposedly another faint galaxy near one of these stars, but it was too faint to see.  Returning to NGC4365 and slewing to the SW, I saw four more galaxies, all easily visible, but I decided not to describe each in detail.

4/23/11  12:48 AM
NGC4526 Galaxy  Vir  Mag 9.6
RA 12h34m03s  Dec +07°41’58”  Size 7.2’x2.3’

At 363x this appeared as a nice, bright, edge-on spiral, with a large, bright core that seemed to be a little lumpy.  The halo was quite elongated and extended.  There is a field star just off the center of the galaxy to the south.

4/23/11  12:53 AM
NGC4535 Galaxy  Vir  Mag 10
RA 12h34m20s  Dec +08°11’51”  Size 6.8’x5’

At 363x this appeared to be another face-on spiral galaxy.  It was large with rather low surface brightness, and I could see 6 stellar pinpoints superimposed on the halo, one of which seemed centered and so could have been the nucleus of the galaxy.  The remaining 5 were undoubtedly superimposed field stars.  The halo exhibited structure, including knots and gaps and an overall swirling character, but I could not explicitly trace spiral arms.

4/23/11  1:01 AM
NGC4546 Galaxy  Vir  Mag 10.3
RA 12h35m30s  Dec -03°47’37”  Size 3.5’x1.7’

Observed at 363x.  This galaxy is quite bright, with a bright concentrated core and a nearly stellar nucleus.  The halo was moderate in size and elongated.  There is a pair of field stars to the SE and another star to the NW.

4/23/11  1:10 AM
NGC4570 Galaxy  Vir  Mag 10.8
RA 12h36m54s  Dec +07°14’46”  Size 4.1’x1.3’

At 363x this is an appealing edge-on spiral.  It has a bright compact core and a stellar nucleus.  The halo is thin and long, oriented SSE to NNW and the NNW tip point towards a bright field star.  A nice spindle-shaped galaxy.

4/23/11  1:16 AM
NGC4636 Galaxy  Vir  Mag 9.6
RA 12h42m50s  Dec +02°41’16”  Size 6.2’x5’

At 363x this has the appearance of a nearly face-on spiral.  It has a large, broad nonstellar core and the halo diffuses gradually into the background.  Averted vision increases the extension of the halo.  I saw some mottling in the halo but no other evidence of spiral structure.  The halo was brighter on the south side of the core compared to the north side of the core.  The south and north sides of the halo are bracketed by two bright stars.  A faint star borders the west side of the halo and a brighter star borders the east side of the halo.

4/23/11  1:23 AM
NGC4643 Galaxy  Vir  Mag 10.6
RA 12h43m20s  Dec +01°58’39”  Size 3.4’x2.7’

At 363x this galaxy has a bright nonstellar core with a small elongated halo.  There is a bright star off the NW edge of the galaxy.

4/23/11  1:28 AM
NGC4660 Galaxy  Vir  Mag 10.9
RA 12h44m32s  Dec +11°11’25”  Size 2.8’x1.9’

At 363x this galaxy exhibited a compact core with a nearly stellar nucleus and a small elongated halo.  It was quite bright, mostly due to the core.  I was unable to see the companion galaxy, IC3711, possibly because by now the 67% gibbous moon had just begun to rise.

 

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