Interest Areas: Visual Observation

Pages

Visual Special Interest Group (VSIG)

Posted on January 28, 2020

Interested in visual astronomy?  Join the HAS Visual Special Interest Group.  Email me at [email protected] to be added to the VSIG email list to receive and send communications to and from all VSIG members.  Check back here for visual astronomy related content including monthly observing challenges and other articles. 

-Stephen Jones – VSIG moderator


Visual Challenge Object Jun 2021 - NGC 5466

Posted on July 29, 2021

June Challenge Object

NGC 5466 – Globular Cluster in Boötes

RA 14h05m27.3s Dec +28deg 32’04”

Size 9.0’ Vmag 9.2

 

As we head toward the summer months and begin looking back toward the halo of the galaxy, our skies become filled with many visual observers’ favorite class of objects: the globular clusters. The summer skies contain several interesting and very bright globulars, like M3 and M5 with their nice bright cores, or M4 with its easy resolvability and unique “bar” of stars in the center.  This month’s challenge target on the other hand does not look like those clusters. 

NGC 5466 was discovered on May 17, 1784 by William Herschel.  It is a very loose globular cluster, ranking class XII (out of XII) on the Shapley-Sawyer concentration class scale.  The individual stars in the cluster are rather faint, with the brightest of them around the 14th magnitude.  The combination of that fact plus the low concentration leads to a considerably low surface brightness, and therefore a considerable vulnerability to light pollution.  I first observed NGC 5466 on my very first night using my 16” Dob back in 2014.  My log entry is as follows:

8/23/2014 10:15 PM – 16” f/4.5 Dobsonian 46x-203x

Very difficult object.  Faint, fuzzy cloud.  Requires averted vision.  Cannot resolve into stars at 46x.  At 203x, now resolved very easily into stars at the limit of my scope's visibility.; Class XII

A year ago when I was one of the 15 or so souls that headed out to the Prude Ranch during TSP week  (no one else was going to be there, so easy to social distance), I made a point of reobserving NGC 5466 in the 16”, and logged the following:

5/20/2020 10:28 PM – 16” f/4.5 Dobsonian 61x

Incredible how much easier this one is here versus Columbus; clearly visible with direct vision; even resolving somewhat; very loose globular, Class XII

My observing skills have improved somewhat since my original observation as well, so I would not suspect today that NGC 5466 is quite as difficult as I made it sound, but nonetheless the striking difference with my observation from West Texas indicates just how much even a slightly brighter sky can have an effect on low surface brightness objects.  NGC 5466 is in a relatively blank area of sky between the constellation Boötes and M3.  The best way to find it is probably just to triangulate its location with ρ and ε Boötis (see first chart below) and then zero in on its precise location looking for the stars near it as shown in the second chart below.   In smaller telescopes it will probably require averted vision to see at all, so noting the field stars is definitely important. 

              

 

The HAS VSIG would love to hear about your own visual observations of NGC 5466.  Send them to the VSIG list server.  To get on the VSIG email list server, contact me at [email protected].

 


Visual Challenge Object - May 2021

Posted on May 12, 2021

NGC 4449 – Irregular Galaxy in Canes Venatici

RA 12h28m11.4s Dec +44deg 05’40”

Size 6.1’x4.3’ Vmag 10.0

This month as we continue through galaxy season we’re going to take a look at one of the most unusual-looking deep sky objects in the sky.  NGC 4449 was discovered by William Herschel in 1788.  It is an irregular galaxy, very similar in morphology to our galaxy’s companion the Large Magellanic Cloud. It is also known to be undergoing a large amount of star formation, likely triggered by whatever disruption caused its extremely distorted appearance. Curiously, John Herschel actually thought (mistakenly of course) that he had resolved the galaxy into its individual stars. 

NGC 4449 is a pretty bright galaxy, comparable in brightness to the fainter Messier galaxies.  The challenge this month is not necessarily in seeing the galaxy, but in seeing just how much of the crazy distorted shape you can make out.  I actually have three different logged observations of this galaxy because every time I look at it, I see something different.  Here’s my log from the last time out:

4/11/2021 1:55 am – 16” f/4.5 Dobsonian 131x

Such a weird galaxy; it's elongated E-W; on the E end it looks like it's splitting apart; on the S there's a little detached section, almost square looking or pixelated; on the N there's a straight filament; between these is just a dark area; it's more put together on the W end.  No bright nucleus of any kind, but it's overall quite bright. 

 

This was definitely the first time the word “pixelated” ever occurred to me while making a visual observation of a galaxy.  I can certainly understand why an observer such as John Herschel lacking current scientific knowledge of the object would think he had resolved it into stars.  NGC 4449 is not especially difficult to locate.  Just look for the stars of Canes Venatici south of the Big Dipper; 4449 is around 1.5 degrees NNW of β Canum Venaticorum.  See the chart below for further reference.

 

The HAS VSIG would love to hear about your own visual observations of NGC 4449.  Send them to the VSIG list server.  To get on the VSIG email list server, contact me at [email protected].

 


Visual Challenge Object April 2021 - Hickson 44

Posted on April 8, 2021

Hickson 44 – Compact Galaxy Group in Leo

RA 10h18m05.7s Dec +21deg 49’57” (position is for NGC 3190)

NGC 3190: Size 4.4’x1.2’ Vmag 12.1

NGC 3193: Size 2.0’x2.0’ Vmag 11.8

NGC 3187: Size 3.6’x1.6’ Vmag 13.4

NGC 3185: Size 2.3’x1.5’ Vmag 13.0

 

Galaxy season is upon us, so this month we will look at a small but interesting group of galaxies in Leo.  These 4 galaxies form the 44th galaxy group in Paul Hickson’s 1982 catalog of compact galaxy groups.  The individual galaxies themselves were discovered much earlier, however.  The two brighter galaxies were both discovered by William Herschel on March 12, 1784.  The fainter two galaxies were discovered by Lord Rosse’s assistant Johnstone Stoney with Lord Rosse’s telescope in January 1850.  A portion of the cluster (particulary 3190 and 3187) was also included in Halton Arp’s catalog of peculiar galaxies as Arp 316. 

The two Herschel-discovered galaxies 3193 and 3190 are bright and should be visible easily in medium-sized scopes.  3187 is easily the most difficult to observe of the 4 galaxies; while 3185’s listed magnitude is almost as faint, its higher surface brightness makes it a good bit easier to observe. Interesting note on 3187: charts show the galaxy’s direction of elongation as perpendicular to that of 3190, but when you observe it you may perceive it to be parallel! The reason for this is that 3187 is a barred spiral, with the bar significantly brighter than the heavily disrupted arms.  The elongation noted on the maps takes the full shape of the galaxy into account; the bar itself is indeed parallel in PA to 3190, and you, like me, may only be seeing the bar.  My log entry is as follows:

4/15/2018 9:57 pm – 16” f/4.5 SCT 131x

NGC 3190 is very bright, elongated; definitely presents as edge-on; NGC 3193 is slightly brighter; more compact, round with stellarish nucleus; NGC 3185 is visible with direct vision, but amorphous; some detail visible with averted; hard to tell what it is, just distorted; NGC 3187 is faintest; requires averted vision to see at all; then only central bar is visible; arms not visible at all

If you’re feeling challenged reading this so far, I do have a bit of good news for you… it’s not particularly difficult to find.  Hickson 44 is located almost exactly in between ζ and γ Leonis in the neck of the Lion (very slightly closer to ζ).  The charts below should get you right there.

                                                                          

 

The HAS VSIG would love to hear about your own visual observations of Hickson 44.  Send them to the VSIG list server.  To get on the VSIG email list server, contact me at [email protected].


Visual Challenge Object March 2021 - NGC 2818

Posted on April 8, 2021

NGC-2818 – Planetary Nebula in Pyxis

RA 09h16m01.5s Dec -36deg 37’37”

Size 93.0”x55.0” Vmag 11.9

 

This month’s challenge object is another off-the-beaten-path object in the southern skies.  NGC 2818 was discovered by James Dunlop in 1828.  It is a planetary nebula nestled within an open cluster, much like the more famous example of M46 and NGC 2438.  Interestingly, the cluster is not listed in the NGC as a separate object, but simply mentioned in the description of the nebula (“in a large cluster”).  Many atlases list both objects as NGC 2818, or one of them as NGC 2818A, but this is not technically correct.  Oddly, when I observed this object myself I made no note of the cluster at all; this may be because I was using the HAS observatory C14 so I may have been at sufficiently high magnification not to even notice the surrounding cluster as a cluster.  The nebula itself is of the two-lobed type like the Dumbbell Nebula M27, though much more “flattened” in shape.  My log is as follows:

4/2/2016 11:22 pm – 14” f/11 SCT 150x

Somewhat faint but still easily visible with direct vision; larger in size; elongated N-S; looks like two long streaks with a dark bar across the middle.  Strong response to both UHC and OIII filters; no central star visible.

 

NGC 2818 is in a bit of a dead area of sky, devoid of many particularly bright stars.  The nearest particularly bright star is ζ Puppis, which is quite some distance away.  However, the nearer stars β Pyxidis, ε Antliae and ψ Velorum are easily visible naked eye from the HAS Dark Site and should provide good starting points for star hopping using a good chart. 

 

The HAS VSIG would love to hear about your own visual observations of NGC 2818.  Send them to the VSIG list server.  To get on the VSIG email list server, contact me at [email protected].

 


Visual Challenge Object February 2021 - NGC 2292/3/5

Posted on April 8, 2021

NGC-2292 – spiral galaxy in Canis Major

RA 06h47m39.3s Dec -26deg 44’47”

Size 3.5’x2.8’ Vmag 11.8

 

NGC-2293 - spiral galaxy in Canis Major

RA 06h47m43.3s Dec -26deg 45’19”

Size 4.2’x3.3’ Vmag 12.3

 

NGC-2295 – spiral galaxy in Canis Major

RA 06h47m23.7s Dec -26deg 44’07”

Size 2.1’x0.6’ Vmag 13.6

 

For the last several months this challenge object column has featured objects that are still relatively bright, perhaps with some challenging details.  This month we’re going to go a little deeper, for a bit fainter, but quite rewarding trio of objects.  These 3 galaxies were discovered by John Herschel in 1835.  The brighter two galaxies are very close together, and are known to be interacting with each other; in deep images the galaxies can be seen to share an outer halo.  The third galaxy NGC 2295 is also physically associated with the interacting pair, and is much closer to edge-on from our vantage point.  The galaxies are roughly 100 million light years from Earth.  My log is as follows:

1/7/2021 10:50 pm – 16” f/4.5 203x

lovely group; NGC 2292/3 is an interacting pair of galaxies very close together; very bright nuclei with small halos; NW-SE of each other; the NW galaxy (2292) is brighter; halos are definitely touching; both direct vision.  To the NW is NGC 2295; very elongated NE-SW; fainter but still direct vision; no obvious nucleus but some superimposed stars; fairly evenly bright and thin

 

This group of galaxies is located in the Southern portion of Canis Major.  I star-hopped to it from Epsilon Canis Majoris (Adhara).  The charts below should help you get there.  The brighter pair of galaxies should be visible in an 8-10 inch telescope from the Dark Site; the fainter NGC 2295 make take a little bit larger scope or darker skies.  If you can’t locate them at first, keep at it!  Challenging yourself can be highly rewarding in this hobby. 

The HAS VSIG would love to hear about your own visual observations of NGC 1365.  Send them to the VSIG list server.  To get on the VSIG email list server, contact me at [email protected].


Visual Challenge Object January 2021 - NGC 1365

Posted on April 8, 2021

NGC-1365 Barred Spiral Galaxy in Fornax

RA 03h33m35.9s Dec -36deg 08’16”

Size 11.3’x6.6’ Vmag 9.3

NGC 1365 is a barred spiral galaxy in the Fornax galaxy cluster, 56 million light-years from Earth.  It was first noted by Australian astronomer James Dunlop (the Southern Hemisphere’s version of Charles Messier) in his 1827 catalog.  It is one of the brightest and largest members of the Fornax cluster.  In my recent investigation of the Fornax cluster for the AL Galaxy Groups program, I observed 1365 last, and found that I had inadvertently left the best for last.  My log is as follows:

11/16/20 12:30 am – 16” f/4.5 203x

Wonderful view; bright round nucleus, with a fainter central bar going roughly NW-SE, a spiral arm coming off the SE end curling back to the north, with a foreground star right in between the arm and nucleus.  The arm coming off the NW end is fainter but also easily seen; both arms are brighter than the bar.  Lovely galaxy.

 

I was so impressed by my view of 1365 on that night that I even bothered to make a sketch of it, which is something I don’t usually enjoy doing.  The primary reason I made the sketch was to verify when I got home that I was really seeing the details I was seeing.  It was quite thrilling to find, upon looking up photos of the galaxy, that my visual impression was spot-on. 

 

Though NGC 1365 is located within the borders of Fornax, it is most easily located from the figure of Eridanus.  It is found just to the west of a triangle of unlabeled 5th-magnitude stars just “downstream” from Upsilon4 Eridani.  See the chart below for further reference. 

 

While you’re in the area, you might as well investigate the rest of the Fornax cluster, as it is actually the next-richest nearby cluster of galaxies in the sky after the great Virgo cluster.  While no galaxy in the cluster is quite as impressively detailed as NGC 1365, several of the other galaxies are at least fairly bright and shouldn’t be too difficult in a moderately-sized scope.  A chart highlighting the brightest members of the cluster including 1365 is below. 

The HAS VSIG would love to hear about your own visual observations of NGC 1365.  Send them to the VSIG list server.  To get on the VSIG email list server, contact me at [email protected].


Visual Challenge Object December 2020 - NGC 891

Posted on April 8, 2021

NGC-891 Spiral Galaxy in Andromeda

RA 02h22m33.4s Dec +42deg 21’03”

Size 14.3’x2.4’ Vmag 10.8

NGC 891 is an edge-on spiral galaxy located 30 million light years from us, within the local supercluster.  It was discovered by William Herschel in 1784.  It is one of the brightest and best-known edge-on galaxies, exceeded in impressiveness only by the Sombrero galaxy M104, and NGC 4565.  However, when I first viewed it several years ago I found it to be a bit more difficult to see than I expected from such a well-known galaxy.  Nonetheless, once it is located it isn’t too hard to see even in a smaller telescope.  I first observed it in 2014 in my 10” dob at 48x and I descibed it simply as “thin streak, with a dark lane in the middle.”  I re-observed it in my 16” just weeks ago at 131x and logged “much lower surface brightness than anticipated, but easily seen direct vision; long and thin, tapering to the points from the central bulge; very obvious dust lane directly down the center; no bright central nucleus; pretty much uniform in brightness; a few stars superimposed.”  NGC 891 can be seen in considerably smaller telescopes than these, though it will be more challenging, and clear dark skies certainly help (both of my quoted observations here were from the HAS dark site).  Key details to notice include the long thin overall shape, and the dark dust lane bisecting the long axis of the galaxy. 

NGC 891 is fairly easily located between Gamma Andromedae (Almach) and Beta Persei (Algol), closer to the former.  It may be even easier to locate if you find the bright open cluster M34 first, as 891 is located almost directly between M34 and Gamma And. 

If you have a large telescope and want a greater challenge while you’re in the neighborhood, just to the SE of 891 on the other side of a 5th magnitude star is the galaxy cluster Abell 347.  This cluster has around 10 members brighter than 15th magnitude. 

The HAS VSIG would love to hear about your own visual observations of NGC 891.  Send them to the VSIG list server.  To get on the VSIG email list server, contact me at [email protected].


Visual Challenge Object November 2020 - NGC 7006

Posted on April 8, 2021

NGC-7006 Globular Cluster in Delphinus

RA 21h01m29.5s Dec +16deg 11’15”

Size 3.6’ Vmag 10.6

NGC 7006 was discovered by William Herschel in 1784.  It is a globular cluster in the outer reaches of the Milky Way’s halo, nearly 135,000 light years from Earth.  Due to its great distance, it appears very small, though it is very bright for its size due to the high concentration of stars.  I first observed it in 2014 with the 12.5” f/7 that used to reside in the HAS observatory.  Though that scope was generally great at resolving globulars, my log entry for 7006 read “small, round, fuzzy; no resolution, very round and fairly concentrated.”  Further research indicates a pretty good reason for the difficulty in resolving it: the cluster’s brightest individual star shines at 15.6 magnitude and most of the stars are fainter than magnitude 18!  Still, thanks to the combined light of the thousands of suns therein, the cluster should be easily visible unresolved even in fairly small telescopes.  Can you bag it?

The HAS VSIG would love to hear about your own visual observations of NGC 7006.  Send them to the VSIG list server.  To get on the VSIG email list server, contact me at [email protected].


Visual Challenge Object October 2020 - NGC 6946

Posted on April 8, 2021

NGC-6946 Spiral Galaxy in Cepheus

RA 20h34m52.3s Dec +60deg 09’14”

Size 11.5x9.8’ Vmag 9.6

NGC 6946 is a face-on spiral galaxy roughly 8 megaparsecs from Earth.  This places it outside the Local Group of galaxies but within the local Virgo Supercluster.  It was discovered by William Herschel in 1798.   In recent years the galaxy has been popularly nicknamed the “fireworks galaxy” because more supernovae have been observed in NGC 6946 than in any other galaxy – 10 supernovae in 100 years.  This galaxy is located fairly close to our galactic plane and is obscured from our view somewhat by gas and dust from our galaxy.  I first observed 6946 in my 16” about 6 years ago in my second night using that scope.  My log read “Faint glow, very low surface brightness.  Oval in shape I think; Can sort of get a hint of some spiral structure with averted vision, but hard to make out. Transparency is getting worse.”  I suspect under better conditions I could probably observe more detail but I haven’t gotten a chance lately to re-observe the object recently.  What do you guys see?