The Coddington`s Nebula

This Member of the Nearby M81 Group Shows an Intriguing Structure 

that Amateur Astronomers can Observe Through their Telescopes

Figure 1. IC 2574, in constellation Ursa Major. Photo by the author.

A summer night in the Northern Hemisphere, the sky looks good for observing deep-sky objects. However, it is important to say that the conditions were not the best at all. I consider important to mention this in case you want to compare your own observation of this faint galaxy with the report posted here. 

This article is devoted to IC 2574 (also  UGC 5666, DDO 81, and VII Zw 330), an interesting dwarf galaxy discovered by the american astronomer Edwin Foster Coddington on a photographic plate using the Crocker Photographic Telescope at Lick Observatory (University of California, USA), in 1898. This object is part of the M81 group which contains 30 members, being Messier 81, NGC 2403, and NGC 4236 the brightest ones (book "The Cambridge Photographic Atlas of Galaxies" by Michael Kônig Stephan Winnewies). M81 group is one of the nearest prominent groups in the vicinity of the Local Group. 

The IC 2574 galaxy is located at a distance D = 4.02 Mpc (1 arcsec = 19.5 pc) according to Karachentsev, Makarov & Kaisina (2013), paper "The Supergiant Shell with Triggered Star Formation in the Dwarf Irregular Galaxy IC 2574: Neutral and Ionized Gas Kinematics" O. V. Egorov,1‹ T. A. Lozinskaya,1 A. V. Moiseev1,2 and G. V. Smirnov-Pinchukov1 (2014).

Figure 2. IC 2574 and its surrounding field.

When you are ready to observe, in a site as dark as possible because we are talking about a faint object, aim your telescope to the region indicated on Figure 1, just north of the Big Dipper. This galaxy lies about 22 degrees from the well known star Polaris.

IC 2574 hosts many HI holes and also an interesting structure to be observed through big telescopes, a Supergiant Shell¹ (SGS) of ∼1000 × 500 pc in deprojected size (Walter et al. 1998; Walter & Brinks 1999; Cannon et al. 2005). The SGS, as well as many holes found in IC 2574, is surrounded with HII regions likely triggered by the stellar feedback related to the star-forming event that occurred in the hole center ∼25 Myr ago (Walter & Brinks 1999; Weisz et al. 2009). The SGS is located in the northwest region of IC 2574 and created by a significant burst of star formation in its center. It is likely responsible for triggering a ring of star formation around it (Walter et al. 1998; Walter & Brinks 1999; Pasquali et al. 2008) See paper "Hunting for Young Dispersing Star Clusters in IC 2574 ", Anne Pellerin, Martin M. Meyer, Daniella Calzetti, and Jason Harris (2012).

A few questions arise now, how much details can we see in this galaxy through an amateur telescope? Are the components of the supergiant shell visible?

This article was written based on observations I made using an 18" (45cm) f3.5 telescope. I first found this galaxy using low power (45x). The group of stars labeled with a circle on Figure 2 was useful to identify the surrounding field and to find the galaxy which was visible at this low power. With a visual magnitude of 8.2 HD 90820 is the brightest star in the 1 degree field of view. 

At 45x, IC 2574 looks like a "rather smooth nebulosity" elongated northeast-southwest with a small area appearing slightly brighter, even though is faint and round. This area is indicated with an arrow in Figure 2 and is the aforementioned supergiant shell. We are talking of a rather faint object even for an 18-inch telescope, at least under the sky conditions in central Oregon in 2018 summer, when this observation was made. It is important to say that the sky conditions were good enough for carrying out this observation but it was not an excellent sky, so maybe observers with the same kind of telescope under a darker and more clear sky might be abble to see this galaxy and its features a little better or easier.

Figure 3. Working with a DSS image I tried here to reproduce 
how the galaxy looked through the 18-inch telescope. Faint target, 
with the two "brighter" areas indicated with squares on the picture.

North is down. South is up.

At 61x the galaxy looks again smooth and clearly elongated, faint in brightness. Using averted vision two areas are slightly brighter than the rest (see Figure 3). However, the whole object is hard to see.

While the structure to the south end looks smooth in brightness and bigger than the other one, the north patch appears round and smaller. Observing carefully, some star-like structures seems to be visible in this region. Figure 4 to the left is a picture taken from the paper  "The supergiant shell with triggered star formation in Irr galaxy IC 2574: neutral and ionized gas kinematics". O.V. Egorov , T.A. Lozinskaya , A.V. Moiseev , and G.V. Smirnov-Pinchukov. This picture shows the giant HII regions on the HST/ACS F658N image of the SGS area according to the list of Stewart & Walter (2000). Bottom panel on Figure 4: location of the star clusters on the same image. The clusters identified by Pellerin et al. (2012) are shown by blue. The red circles denote the clusters from Cook et al. (2012). The four largest green circles show the star clusters identified by Yukita & Swartz (2012).

121x. This is an intersting magnification to see IC 2574. It is a faint object so averted vision is always necessary to glimpse and identify its structures. A very challenging glimpse of a small nebulosity is possible for moments when observing carefully, I´m talking about [MH94a]³ IC 2574 203 and [MH94a] IC 2574 218, a small object composed of two HII regions. The bigger structure, to the south, looks again smooth (featureless). Although faint, the smaller northern feature is a little easier to detect, appearing slightly more detached against the surrounding stars. Some of the components on that zone (appearing star-like in shape) are barely visible. Using averted vision, PMC2012² 13z, the brightest component according with what can see on a DSS image, seems to be the "easiest" part to pick up visually. PMC2012 13z is a star-forming complex – an extended (∼ 450 × 320 pc) fine-filamentary HII region, located in the northern wall of the SGS. Yukita & Swartz (2012) identified the young star cluster C1 inside Region.

162x. At this power the small object composed of two HII regions

Figure 4. Credit O.V. Egorov et al. 

 is visible with averted vision (see Figure 5). It is a faint feature of the galaxy however. At this magnification the aforementioned areas of the galaxy seems to be connected by faint nebulosity, without a doubt part of the galaxy, appearing clearly elongated. Observing carefully, some components of the supergiant shell seem to jump to the view but it is not possible to see them clearly and discern and identify each one. The component of the supergiant shell, PMC2012 13z, an association⁴ of stars according to SIMBAD Database and the STScI Digitized Sky Survey web page is certainly visible appearing cuasi-stellar in size and with a hazy nature. The UHC filter slightly improves the view of the smaller patch of the galaxy. Even PMC2012 13z appears more nebulous.

Both the STScI Digitized Sky Survey web page and SIMBAD Database agree that CVL2009⁵ UGC 5666-3, the brightest nebula in the SGS, is an HII region that looks rather non-uniform and consists of a central nebula ≃ 120 pc wide, several more compact (≃ 10 − 20 pc) clumps that surround it, and two faint external shells southeast and northwest of the region with the sizes of ≃ 20 pc and 35 pc.

Figure 5. The supergiant shell and its main components.

Another association of stars, PMC2012 21z, is a region that has the form of a bright ‘halfshell’ whose eastern part adjoins the dense wall of the SGS, with a fainter filamentary inner part. The full size of the region is about 250 × 150 pc.

While some star-like structures seem to be visible briefly and with difficulty in this galaxy, as was mentioned above, the view is difficult and unclear, so I can not claim to have identified these last two features of the SGS visually. The only patch visible there seems to be the brightest one on Figure 5, PMC2012 13z. 

IC 2574, one of the many outstanding and enigmatic galaxies that we can find in a dark sky, is a good target to put your eyes and telescope under proof and see how much you can detect under ideal observing conditions.

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1_ SGS Irregular galaxies reveal giant HI supershells and holes with sizes as large as 1 – 2 kpc and lifetimes up to several hundreds Myr. Giant supershells and holes in some galaxies represent the dominant feature of the ISM. Such large structures are usually called supergiant shells (SGS), or giant supershells. Formation mechanisms of supergiant shells have been discussed extensively in recent decades

2_ [PMC2012] - (Pellerin+Meyer+Calzetti+, 2012)

3_ [MH94a] (Miller+Hodge, 1994)= (MH)as appears in SIMBAD Database

4_ The concept of a stellar association was originally introduced in 1949 by V. A. Ambartsumian, who later separated them into OB and T associations (Ambartsumian 1968). Morgan, Sharpless, & Osterbrock (1952) considered as a stellar association any loose group of stars within an area where bright OB stars exist and with evidence of a common origin.

A recent definition of a stellar association (Kontizas et. al. 1999) refers to it as a single, unbound concentration of early-type luminous stars, embedded in a very young star forming region.

5_ [CVL2009] - (Croxall+van Zee+Lee+, 2009)as appears in SIMBAD Database

N79 & N83 Complexes in LMC

A Visual Observation of Interesting Structures in the Large Magellanic Cloud. Researchers Say one of Them Could be a Rival of 30 Doradus Nebula

Figure 1. The Complexes under observation

Early March, it is dark enough now (around astronomical twilight), so the Large Magellanic Cloud looks amazing, high in the southern sky. I am ready to aim the telescope (8-inch in diameter) to the west region of this galaxy, where the arm W is situated, to find and observe in detail other interesting complexes of our nearby galaxy (i.e. LHa120¹-N79 and N83). The extent of these regions are outlined in Fig. 1b in the paper "Ultraviolet and Optical Observations of OB Associations and Field Stars in the Southern Region of the Large Magellanic Cloud", Joel WM. Parker  et al. (2000). In the 1° field of view (Figure 1) the white-blue star HD 31518 (magnitude 7.2) is the brightest one. Near the center, LHa120-N79 is visible along with its companion LHa120-N83, both are small regions of nebulosity with N79 appearing more prominent and "wide". These complexes reside in a bigger structure named Shapley VII, one of the giant stellar and gaseous groupings of the LMC that has an angular dimension of 48x25 arc min (PA 90°). Shapley VII lies in an even bigger structure named SGS² 7 that has an angular dimension of 55x55 arc min. In the field of view, toward the East of these complexes, a region showing a higher concentration of very faint stars embedded in subtle nebulosity, elongated East-West, can be detected. We are talking about LHa120-N94 which includes the OB association³ LH⁴8, which encloses, in turn, the cluster of stars NGC 1767, discovered by John Herschel. A few brighter stars are superimposed in that region. This region seems to be connected to the two main nebulosities by very subtle nebulosity.

N79 is an irregular HII region, roughly 17x14 arc min in size, that contain the OB associations LH1 (also NGC 1712) and LH2. Its coordinates are R.A. 04h 52m 00s Dec. -69° 22` 30" (J2000.0). This region has a star formation efficiency exceeding that of 30 Doradus by a factor of ∼ 2 as measured over the past 0.5 Myr. The first observation of this object was made at low magnification (42x). The animation below showing the N79 complex (Figure 2) was made using a DSS image to show what I think it could be nicknamed the "Magellanic Horsehead Nebula" because it resembles, in my opinion, the profile of a horse. That section of the complex is called LHa120-N79E and is the most prominent one (see Figure 4), appearing as a rather elongated nebulosity E-W. Using averted vision the nature (as a nebula) of this object is more obvious, appearing somewhat wider and more contrasted. Some of very subtle nebulosity seems to lie in a small area southwest of LHa120-N79E. Higher magnification and nebular filters will surely help for a more detailed description of this area.

Figure 2. Zoom in  into LHa120-N79, a complex in LMC.

Using the same magnification we move to the complex N83, situated about 15 arc min northeast of N79.  Henize (1956) identified four ionized gas regions lying in that direction (N83A, B, C, D). Lucke & Hodge (1970) detected an OB association (LH 5) spanning over 16 square minutes (3600 square pc) around N83. It contains 26 blue stars (Lucke 1974) the brightest of which is Sk-69◦30 (Sanduleak 1970), a G5 Ia with a visual magnitude of 10.18 so it is the easiest star to see of three that are visible there (see paper "HST study of the LMC compact star-forming region N83B" by M. Heydari-Malayeri et al.). Another one of the three stars looks like a small roundish nebulosity where a star is visible within it when using averted vision. Actually, that star, Sk -69 25, is the main exciting object of the mentioned nebulosity which is known as N83A, also NGC 1743 (seeFigure 6). 

At the same magnification a nebular filter, like UHC, improves the view of both complexes. N79E is visible, with averted vision, as a rather elongated nebulosity where a couple of stars are glimpsed for moments. With a similar configuration of that in N83 complex, three stars can be detected in the N79 area, to the south of N79E. One of them looks actually like a star embedded in a small and round nebulosity, this object is MCELS⁶-L25 (see Figure 4), while the other ones are the 10.7 magnitude blue supergiant HD 268718 and the 8.5 magnitude HD 31722. The whole area seems to be engulfed by very subtle nebulosity. 

Back in N83, the component N83A looks like a small nebulosity while the entire star-forming region seems to be engulfed by some nebulosity also.

Figure 3. The object H72.97-69.39.

Picture courtesy of Bram B. Ochsendorf.

Taken from the paper "The Star Forming

Complex N79 as a Future Rival of 30 Doradus" 

written by him and his team and included here

with his permission. 

The so-called high excitation blob⁵ N83B (also NGC 1748) which lies about 2.5 arc minutes north-east of N83A (Figure 6), and is around 25 light years in diameter, probably represents the most recent massive starburst in the giant HII complex N83 and the OB association LH 5. Heydari-Malayeri et al. (1990) discovered a compact HII region toward N83B. This object, which they named N83B-1, turned out to be a member of the so-called high-excitation blobs (HEBs) in the Magellanic Clouds. The brightest blob is the compact HII region N83B-1.

The zone of LH8 shows, through a UHC filter, smooth nebulosity, being more obvious toward the edge of the eyepiece field and less visible (maybe absent at all) in the zone between it and the complexes under study.

Now, a view of MCELS-L25, situated close to the 11.8 magnitude star RMC 54F (according to SIMBAD Database), with higher magnification (78x), shows a very small and detached hazy patch that looks brighter toward its center. N79E looks like an elongated structure where some stars, members of the OB association LH2 (NGC 1727), are embedded and associated with the nebulosity. Averted vision improves the view of this section.

Through this eyepiece, giving 78x, only N83A appears like a roundish object, compact, and with a hazy appearance. Some of nebulosity is hard to detect in the area where the object MCELS-L55 lies. 

Applying a UHC filter, the view of N79 and, in particular, N79E is very interesting. N79E is, by far, the most prominent feature there, where faint stars member of LH2 can be glimpsed using averted vision. For moments, and of course using averted vision again, the component N79D can be barely seen, very faint and round in shape. The star cluster KMHK 187 is associated with this nebulosity according to SIMBAD Database. MCELS-L25, through this magnification and filter, looks like a small hazy spot with a star-like brightness at the center.


H72.97-69.39, a precursor to the R136 cluster in 30 Doradus? 

At the heart of the large-scale complex N79 lies an extremely luminous object which immediately draws parallels to the central cluster of 30 Dor, R136 (Nayak et al.) (See Figure 3). Bram B. Ochsendorf and his team refer to it as ‘H72.97-69.39’ (I indicate it with red letters in Figure 4). This object is more luminous than any MYSO⁷ or compact H II region discovered with large-scale IR surveys of the LMC and Milky Way (read more in the paper "The star-forming complex LMC-N79 as a future rival to 30 Doradus" by Bram B. Ochsendorf et al. 2017). So, if you observe this region of the Large Magellanic Cloud with your telescope, remember that a peculiar and intriguing object resides there.

Figure 4. LHa120-N79 components

At this magnification (78x) and UHC filter, N83A is clearly visible being the most conspicuous feature (in brightness) of the whole complexes. It looks, as with lower magnification, like a round and small nebulosity with its star at the center. A very challenging object, difficult to see, is MCELS-L55, appearing like a ghostly round patch using averted vision.

There is a good view of the nebulosity in N79E using the Orion Ultrablock filter. Through this filter the stars associated look a little more clear. N79D is an elusive object and it could not be clearly visible at this magnification and this filter. On the other hand, MCELS-L25 appears like a small patch of nebulosity close to the 11.8 magnitude star RMC 54F.

In the complex N83, N83A is visible with not difficulty appearing more bright and nebulous than its counterpart in N79 complex. N83A reminds me a kind of small and bright planetary nebula. MCELS L-55 is elusive and a challenging object through this filter also. It seems to show up very briefly but I can not assure it is visible. It is, without a doubt, a good test for rods in your eye.

Using higher magnification...

Figure 5. N83B detailed image
Credit: M Heydari-Malareri & NASA/ESA.

106x is a good magnification to see the whole structure in the field containing the two complexes under study. Now the association LH2 and the associated nebulosity is visible in more detail. The star CTIO85 263 (visual magnitude 12.4 according to SIMBAD Database), is the brightest one visible in that association through an 8-inch telescope (indicated with an arrow in Figure 4). N79D is barely detected using averted vision, appearing seemingly round in shape. At this power, N83A looks now like a small and compact stellar cluster.

Through a UHC filter N79E looks faint, hazy, and without stars. The nearby structure N79D can be detected using averted vision but still elusive, faint, and challenging. It appears like a round structure separate from N79E by no nebulosity.

N83A looks bright, nebulous, and rather round in shape.

Figure 5 is a composite image of the region N83B taken by HST/WFPC2. The brightest blob is the compact HII region N83B-1 and the fainter one below it (∼100 in size) is N83B-2. The small arc-nebula further south, centered on a relatively bright star, is N83B-3.

Figure 6. LHa120-N83 components

A final observation of the complexes using 166x allowed me to see even more details. The component of N79, MCELS L-25, seems to be composed by two "star-like" objects, like two slightly defocused stars. N79E is visible with more detail, showing several stars embedded in faint elongated nebulosity. N79D is again visible, round, faint, and displaying smooth brightness. Averted vision is necessary.

N83A is clearly visible showing some faint nebulosity in its outer part. The section named MCELS L-55 is hard to see, challenging and faint. A few stars seem to be glimpsed embedded in extremely faint nebulosity.

Orion Ultrablock filter and averted vision make it possible to see two objects associated with nebulosity in MCELS L25. The view of N79D through this filter seems to get worse with respect to that obtained without any filter.

Another stunning formation in our satellite galaxy awaits to be seen by observers with telescopes during a clear night in the southern hemisphere summer.

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1_  LHa-120 N- This is the full name of an entry in the Henize catalogue of LMC emission nebulae. "L" refers to the Lamont-Hussey Observatory of the University of Michigan; "Ha" means the Hydrogen-alpha emission line, the key signature line used in the survey; "120" refers to the plate number (objective prism plate) for the LMC; "N" labels the object as a nebula, as distinct from a star (label "S").

2_ SGS are the supergiant shells, the largest of complex filamentary structures in irregular and spiral galaxies, indicative of a violent ISM, with diameters approaching 1 kpc (Goudis & Meaburn 1978). SGSs are thought to be formed by the fast stellar winds and supernova explosions of multiple OB associations.

3_ OB Association: The concept of a stellar association was originally introduced in 1949 by V. A. Ambartsumian, who later separated them into OB and T associations (Ambartsumian 1968). Morgan, Sharpless, & Osterbrock (1952) considered as a stellar association any loose group of stars within an area where bright OB stars exist and with evidence of a common origin.

A recent definition of a stellar association (Kontizas et al. 1999) refers to it as a single, unbound concentration of early-type luminous stars, embedded in a very young star forming region.

4_  LH is a catalogue of OB associations in the Large Magellanic Cloud compiled by Lucke & Hodge.

5_ The compact HII regions called High-Excitation Blobs (HEB) constitute a rare class of ionized nebulae in the Magellanic Clouds. They are characterized by high excitation, small size, high density, and large extinction compared to typical Magellanic Cloud HII regions. These objects are tightly linked to the early stages of massive star formation.

6_ MCELS means "Magellanic Cloud Emission Line Survey". This is a joint project of Cerro Tololo Inter-American Observatory (Chile) and the University of Michigan using the CTIO Curtis/Schmidt Telescope.

7_ MYSOs stands for Massive (>8 Msolar ) young stellar objects.

The NGC 3256 Group

A Tidally Disturbed Galaxy, a Galaxy with a Double Nuclei, and Other Distant Members are a Group of Enigmatic Galaxies in the Southern Skies to be Explored by Amateur Observers

Figure 1.Pointing toward the zone where the galaxies are situated, in constellation

 Vela

In the eastern part of constellation Vela (the Sail) a group of faint galaxies (at least for an 8-inch telescope) can be found. March is a good month to observe this constellation because it is at a very good altitude as soon as the sky gets dark, so you can observe objects there for several hours during the last nights of the summer in the Southern Hemisphere. To find the area where this galaxies lie is easy because you can use one of the bright stars of Vela, the 2.7 visual magnitude m (mu) velorum,  a class G (G5) yellow-white giant. From there we can move to the stars HD 92139 and HD 91504 (visual magnitudes 3.8 and 5 respectively) to finally find the faint pair of stars of magnitudes 5.7 and 5.9 that are visible from any site that offers dark skies. Once there, the field of interest (centered at R.A. 10h 29m 25s  Dec. -44° 20`32") is roughly 52 arc minutes northwest of the mentioned pair. The galaxies are distributed roughly South-North (see Figure 3 below). Some researchers state that two groups of galaxies lie there, NGC 3256 and 3263, but are difficult to distinguish from each other spatially. However, many researchers consider at least 15 galaxies to be members of a single large group spread over roughly a few degrees that is called the "NGC 3256 group of galaxies". According to a group of researchers led by Jayanne English, "The most spectacular HI feature in the NGC 3256 Group is a galaxy-sized intergalactic HI cloud (English 1994), which we will refer to as “the Vela Cloud.” The structure, as projected on the sky, is not clearly associated with an individual galaxy but appears to be part of the group" (see the paper "The Vela Cloud: A Giant HI Anomaly in the NGC 3256 Group" (2010).

At low magnification (42x) the field does not show any bright and conspicuous galaxy. Focusing on the southern edge of the field of view (see Figure 3) a very faint hazy patch, somewhat elongated, can be glimpsed. Four stars in a row or a chain seems to lie there, among the galaxy. One of them seems to be the core of the galaxy (see Figure 2). Averted vision is necessary for a better detection. That is the  barred galaxy NGC 3261, discovered in 1836 by John Herschel. An historical identification by Dreyer is "faint, small, round, among stars". SN 2008fw, a supernova of type Ia, was discovered in this galaxy in 2008.

Figure 2. NGC 3261
Credit: The Carnegie-Irvine Galaxy Survey (CGS)

Moving about 15 arc minutes due north another galaxy very small in size (1.90 x 0.5 arcmin , PA: 135 ) resides, NGC 3256B, a  type SBbc galaxy with a magnitude of 13.0 (Data from Wolfgang Steinicke's Revised NGC and IC Catalog). It was not visible through this instrument at the different magnifications used during the observing session (from 42x to 266x). 

Moving farther north, another 18 arc minutes, we find a tidally disturbed galaxy, NGC 3263 (m_v: 11.1mag , SB: 11.8mag per square arcmin), included in category 7b "Jets from Spirals" in the Catalogue of Southern Peculiar Galaxies and Associations by Arp & Madore. At this magnification the galaxy is extremely difficult to detect visually. A very faint hazy structure seems to be there when viewing with averted vision. A close companion, NGC 3262, was not visible.

Reaching the northern edge of the field of view we find, at least on nice deep astrophotos, a couple of galaxies (i.e. NGC 3256 and 3256C), see Figure 3. The last one was not detected at this magnification. Although it is a faint galaxy, NGC 3256 (also AM 1025-433) is the "easiest" member of the group in the field appearing round and rather smooth in brightness when using averted vision. A. J. Mulia et al.  in their paper "Star Cluster Formation and Destruction in the Merging Galaxy NGC 3256" (2016) state that NGC 3256 is a merging pair of galaxies ≈ 36 Mpc away and the most luminous LIRG¹ in the local universe.  The main body of NGC 3256 contains a dense population of clusters, many of which are embedded in the galaxy’s dusty interstellar medium. This galaxy shows two long tidal tails in optical photographs (e.g., Sandage & Bedke 1994).

Figure 3. DSS image of the galaxies in the field

These are, without a doubt, faint galaxies to be observed with an 8-inch telescope at low magnification, being only NGC 3261 and 3256 glimpsed in such a condition. Higher power is necessary for a more fruitful analysis of these distant objects.

At 78x, NGC 3261 is visible faint but with direct vision. It is situated among three stars (see Figure 2 above). Using averted vision, NGC 3261 looks rather round in shape. A small structure, slightly brighter, seems to lie in its interior.

NGC 3263 is a faint member detected using averted vision that makes possible to see it rather elongated with its central zone somewhat brighter.

NGC 3256C, a SBcd type galaxy, was not visible at this magnification. Its magnitude is 12.6, SB: 13.2 (mag per square arcmin).

The galaxy NGC 3256 is visible with direct vision at this magnification. Averted vision of course helps for a better detection. It looks round with a brighter core.

An observation at 106x shows NGC 3261 clearly distinguished from the surrounding stars. It is round and wider than NGC 3256. Toward its center the brightness increases and for moments a star-like structure shows up when observing carefully.

Figure 4. NGC 3263
Credit: The Carnegie-Irvine Galaxy Survey (CGS)

NGC 3263 and its companion NGC 3262 (which is not visible at this power) are visible on the picture to the left. NGC 3263 looks elongated for moments when is observed with averted vision and its brighter zone within it is again visible.

NGC 3256C is not visible while the nearby companion, NGC 3256, is easy to see at 106x, round and with a bright core.

A new analysis of the galaxies using even higher magnification was carried out. At 166x NGC 3261, which looks faint and round, shows a small "granulated" structure when using averted vision. Two stars, very faint and elusive, are visible there for moments.

NGC 3263 is still a faint and elusive galaxy, better viewed using averted vision. At 166x its elongated shape was not clearly discerned.

Figure 5. NGC 3256
Credit: The Carnegie-Irvine Galaxy Survey (CGS)

Is NGC 3262 visible through an 8-inch scope? 

You know that a faint galaxy, a challenging object for a given type of telescope, can be hard to see or glimpsed. The degree of difficulty will depend on how dark, steady, and clean is the sky when you are observing. According to an optimum detection method, an observer under a 6.2 limiting magnitude sky should detect this small galaxy, a companion of NGC 3263 (see Figure 4), using around 100x. Even if it was not a clear image at all, a very small hazy patch, round, seems to be barely seen for moments using averted vision. I was very careful identifying the nearby stars surrounding that target to realized if the gosthly image I glimpsed is the small lenticular companion of NGC 3263. It was also barely visible at higher magnification (266x). Observers with 8-inch telescopes are encouraged to observe this galaxy and get their own conclusion about its visibility. Even though NGC 3256B has the same magnitude than NGC 3262, it was not detected through an 8-inch telescope that night. Maybe the reason is that NGC 3256B is a little bigger in angular dimension (1.90 x 0.5 arcmin). NGC 3256C, with its magnitude of 12.6 and surface brightness 13.2 (mag per square arcmin) should be visible in an 8-inch scope, but for some reason it was not visible during the entire observing session. 

NGC 3256 is clearly visible showing its bright core that for a moment looked offset (maybe suggestion of the more expanded structure of the galaxy visible upper left on Figure 5?). NGC 3256 is included in Category 15 "Galaxies with Tails Loops of Material or Debris" in the Arp-Madore Catalogue of Southern Peculiar Galaxies & Associations. This galaxy also has a peculiar feature, a double (northern and southern) nuclei. Presence of an AGN² at the optically obscured nucleus has been suspected for a long time. AGNs are often found among LIRGs.

Figure 6

A final observation of NGC 3261 at 266x makes possible to see the two aforementioned faint stars in the central region of the galaxy which looks round and smooth in brightness.

NGC 3263 looks, with averted vision, elongated. Brighter areas in the galaxy briefly jump to the view.

The central zone of the merging galaxy NGC 3256 looks rather smooth in brightness. Fainter structure of the galaxy is visible surrounding its core.

In the silence of the vast Universe, these galaxies await being observed by amateur astronomers from sites far away from big urban centers.

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1_ LIRG (Luminous Infrarred Galaxies)are galaxies with luminosities above 10¹¹ L_☉. These galaxies emit more energy in the infrared portion of the spectrum, not visible to the naked eye. LIRGs are more abundant than starburst galaxies. Infrared galaxies appear to be single, gas-rich spirals whose infrared luminosity is created largely by the formation of stars within them. However, some galaxies' luminosity comes from an active galactic nucleus or AGN.

2_ AGN (Active Galactic Nuclei) are galaxies where the nucleus (or central core) produces more radiation than the entire rest of the galaxy. Current theory suggests that there is a supermassive black hole (millions of times the mass of the sun) at the center of AGN.