Striking Nebulae in the Large Magellanic Cloud

Published in the April 2013 issue of the Rosette Gazette newsletter (Rose City Astronomers, Portland Oregon USA)

Bright Emission Nebulae and a Supernova Remnant

are Found in the Northeast Region of our Satellite Galaxy

The sky is getting darker at Uspallata Valley1, in central-west Argentina. Slowly, the Magellanic Clouds become visible in the Southern Sky. Hidden not too far from the heart of the Large Magellanic Cloud (LMC) an interesting complex of small nebulae resides. The question arises, how much you can see there with a common 8-inch telescope? Is this area of that galaxy impressive enough to observe and study with this kind of optical instrument?

I have tried to describe in this article all the details you can observe in this complex, in fact, one of the most interesting within our satellite galaxy.

The Southern Sky in summer. The Large Magellanic Cloud (right on the picture) is an astounding unaided eye object, together with the Eta Carinae Nebula (upper) and the Coalsack Nebula (middle left). Photo by the author.

I spent two nights, March 8 and 9 (2013), to observe a small region centered at R.A. 05h 39m  Dec. -67° 40', which corresponds to the “area 24” of my big observing project about this galaxy. Using an 8-inch telescope and an eyepiece that gave me 37x and a wide field I got a first view of the zone. At that moment, the galaxy was 48° above the horizon. The stars in the field mostly have visual magnitudes fainter than 11. The star HD 38616, with a visual magnitude of 7 (Figure 1), is the brightest one there. On the west edge of the eyepiece field, a nebulae complex is easily visible even without filters. It is, by far, the most conspicuous feature in the field.

The N59 Nebula

Figure 1. The region under observation is situated to the north of 30 Doradus 

(Tarantula Nebula). North is up.

Named LHa-1202 N59, and also known with the name of “Dragon’s Head Nebula”, this HII region is centered at R.A. 05h 35m 25s  Dec. -67° 35' 00´´, at the boundary with the structure known as LMC-43.

Focusing on this complex, three patches are visible at 37x. The brightest and biggest zone, known as N59A (see Figure 2), exhibits the shape of a fan with several filaments which may be ionization fronts, thus making it the third brightest nebula of the LMC after 30 Doradus and N11. It is composed of two regions or maybe just one big region elongated roughly west-east with a dark lane across dividing it into two parts of similar brightness. These two parts have NGC numbers, 2035 and 2032. The first one was discovered by James Dunlop in 1826. The other one, NGC 2032, was observed by John F. W. Herschel in 1834 but surely Dunlop observed it too because it is very similar to the other area discovered by him. “The dust lane seems to be mixed in with the nebular gas and the stars, suggesting a site where star formation may still take place. However, from the morphology revealed by those direct images, it is impossible to ascertain whether those nebulae are physically related or even, whether they are located at the same distance” (extract from the paper “Kinematics of the very young nebula N59 at the edge of the supershell LMC-4” M. Rosado et. al. 1998). N59A is closely related to the OB association4 LH 825, which covers an area of 3´x 6´ and virtually coincides with the nebula.

Figure 2. N59 complex. North is up

A third patch, round in shape through an 8-inch scope, that looks fainter than the other two, lies about 5 arc minutes to the East of the brightest part of the complex, in the region known as N59B (see Figure 2) which is, according to C. Armand, L. Deharveng and J. Caplan in their paper “The Stellar Content of the Large Magellanic Cloud HII Region N59A” (Astronomy & Astrophysics, 1992), a filamentary nebula that includes a photoionized region in the north, a supernova remnant in the south, and a Wolf-Rayet star. The photoionized patch I saw is known as NGC 2040, a diffuse nebula discovered by James Dunlop in 1826 using a 9-inch telescope.

At 48x, the view is more detailed. In the brightest area divided by the dark lane, the eastern patch (NGC 2035) looks slightly smaller while the western patch (NGC 2032) appears bigger, showing two stars at its western edge. An extension of fainter nebulosity, which becomes narrower toward the West when seen through an 8-inch telescope, is visible at this power. I am speaking of NGC 2029 (see Figure 2). On the other hand, NGC 2040 was clearly seen, fainter than the other patches and with smooth brightness. With averted vision, a very small spot seems to lie very close. Maybe the two stars in the region of the supernova remnant? Read more below in this article.

Applying higher magnification (64x) I got a beautiful view of this complex. NGC 2032 and 2035 look very bright. Although both nebulae together are slightly elongated west-east, NGC 2032 specifically is a bit elongated north-south. Even if the overall shape of NGC 2040 is round, at this magnification some clues of irregular shape appear. The small and faint region known as N59C (see Figure 2) could not be visible at this magnification.

In the second observing night I applied UHC filter to this eyepiece to observe this complex. I started the observation at 10:35pm local time (UT-3hours) with the Large Magellanic Cloud at 47° of altitude in the sky. The view was very clear, with the patches NGC 2032 and 2035 obvious in the eyepiece. NGC 2029 is visible as a smooth nebulosity while NGC 2040 is more easily visible than the view with the other eyepieces. Through this filter, it looks slightly fainter than NGC 2032/35. With averted vision, a bright dot is visible within the nebula, maybe a star member of the OB association LH88 associated with NGC 2040. This filter improves the overall view of the complex, being especially useful for a better view of NGC 2029 that shows a triangular shape, getting narrower outwards of the brightest part of the complex. Although it was difficult, the view of N59C, a small, round, and faint nebulosity in the southeast part of the pair NGC 2032/2035 was possible at this power using this kind of filter.

Through an Orion UltraBlock filter N59 looks very well. Like the UHC filter, this one improves a little the view of the whole complex. However, it can be observed without a filter as well. This filter helped for the observation of the two faint nebulae NGC 2029 and 2040.

I spent most of the second night (March 9) observing these nebulae with higher magnification. At 120x, the view of N59 is more interesting and detailed. Each region or patch is clearly visible and identified. NGC 2040, which shows a similar brightness to NGC 2029, and fainter than the two main patches, shows some faint stars embedded in the nebulosity. It is surely the aforementioned OB association LH88 (Lucke & Hodge 1970).

Aiming the telescope to NGC 2032 & 2035, both nebulae look outstanding at this power. NGC 2035 looks round while NGC 2032 appears a bit elongated. C. Armand et. al. point out that the main star that excites the region N59A is an O5 spectral type they name “star 226” in their paper. I indicate it in Figure 2 with a small red circle. The detached black lane between the bright nebulae adds an interesting view to the region. NGC 2029 looks faint at this magnification, being better viewed using averted vision.

Figure 3. The [S II]  emission (yellow) defines the supernova

remnant. Picture from Smith et. al. 1999. North is up.

With a UHC filter, NGC 2029 and NGC 2040 show similar brightness. A slightly brighter region is visible within NGC 2029 (look Figure 2). For a brief moment, a star is visible within NGC 2040. On the other hand, N59C is still difficult to see even with this filter, being necessary averted vision.


An Extragalactic Supernova Remnant

A supernova remnant, known as SNR 0536-676, is situated in this complex. It was identified as such by Mathewson et. al. (1985). It appears to be a blow-out of the dense HII region N 59B around the OB star association LH 88 (Chu & Kennicutt, 1988).

I invited my friend Carlos Gutierrez to observe this elusive object using a 16-inch telescope. A first observation at 106x made possible to identify two very faint stars situated in a key position to try to delineate the shape and size of the supernova remnant. They are indicated with the red arrow in Figure 3. After that, we tried to see some nebulosity in the region immediately to the South and West of NGC 2040. However, it was impossible to view at this magnification and under the observing conditions that night. Using a UHC filter with this eyepiece, an extremely faint, elusive, and small nebulosity could be glimpsed in the region indicated by the ellipse in the picture, which is coincidental with the brightest portion of the supernova remnant. The view was very difficult and it was close to a “retinal torture”.
This elusive nebulosity is also visible in the DSS image in Figure 2. There it looks a little brighter than N59C but it was harder to see even through this bigger telescope. The nebulosity labeled with the square in Figure 3 was also visible using averted vision for both of us. Carlos stated that it has a triangular shape, narrowing toward NGC 2040. According to the picture, this nebulosity seems to be not a part of the supernova remnant, but an extension of the NGC 2035 region.

Figure 4. N70 nebula. North is up

At 144x, the two stars are clearly visible and another star (to the North) is also detected. The small patch close to the stars is visible for some moments. The zone enclosed by the square shows a faint star within (visible in Figure 3). With a UHC filter, the view is similar to that at 106x.

The N70 Nebula

Also known as DEM L6 301, it is one of the most outlying bright emission-line objects, located in an isolated region of the disk, far from supergiant shells (Meaburn 1980), H II regions, and bright diffuse H-alpha emission, a textbook example of an isolated superbubble. “It is an especially prominent bubble of line-emitting gas which appears to be powered by a population of hot massive stars in its interior” (paper, "Emission-Line Properties of the LMC Bubble N70", B. Skelton et. al. 1999). To observe this object you need a very dark sky, good dark adaptation, and patience to detect the faint nebulosity situated 45 arc minutes to the southeast of N59.

Figure 5. The cluster NGC 2053 (left). North is up.

At 37x, the view of this nebula was interesting. It looks faint on DSS (Digitized Sky Survey) images and it is extremely faint when you try to see it visually under a dark sky. It can be hardly glimpsed even without a nebular filter through an 8-inch telescope. A good way to find it is to identify the triangle of stars (lower edge in Figure 4), and then to move about 15 arc minutes to the North. Once there, you will be able to identify a close pair of stars with visual magnitudes 10.8 and 12.5 (white arrow in Figure 4). Very close to it, a faint nebulosity can be glimpsed using averted vision. Two stars within the nebulosity are also visible, one of them looks like a defocused faint star and is coincidental with the position of the OB association LH 114. This is an association consisting of at least nine stars of type B0 or earlier (Oey 1996a).

At 48x, I could clearly identify the double star. Observing in the area of this nebulosity, a very small and compact stellar group is detected where LH 114 lies. This compact group appears surrounded by a faint and smooth nebulosity, N70.

At 64x, in the central zone within the faint nebulosity, a sort of “defocused star” can be glimpsed. For a moment, and using averted vision, 2 or 3 stars very close to each other seem to lie in the zone. At this magnification and using a UHC filter, N70 looks a little more detached from the surrounding sky, but it is a very faint object. Averted vision suggests its round shape, showing a smooth and faint brightness. At the center of the nebulosity, the small region slightly brighter is easily distinguishable.

Through an Orion UltraBlock filter, the view is very similar. The stellar nature or content of the small central region embedded in nebulosity can be confirmed.

How does N70 look using 120x? Well, the stellar configuration mentioned above is easily identified in the eyepiece field and the faint nebula can be glimpsed, showing smooth brightness and engulfing the stars there. LH 114 appears like a small and compact stellar group, and some members can be spotted using averted vision. The view with a UHC filter is not very different.

In the outskirts of the complex N59, to the northeast, two small hazy spots are visible. Averted vision helps to see them better. According to the DSS image one of them, indicated with a red arrow in Figure 5, is a group of 3 stars surrounded by faint nebulosity. At low power (37x) and using averted vision it looks nebular and a little elongated, suggesting the 3 stars in a raw. Higher magnification is necessary to see it in detail. I personally don´t know if these stars are members of the OB association LH 92. I could not find detailed information about this association, but the DSS image obtained from http://archive.stsci.edu/cgi-bin/dss_form shows the area of the three stars as the place of LH 92. The other one is the open cluster NGC 2053 (see Figure 5) discovered in 1837 by John Frederick William Herschel, an object with a magnitude of 12.2 according to the NGC/IC Project web page and the Wolfgang Steinicke's Revised NGC and IC Catalog. The zone of the two objects seems to be connected with faint nebulosity. The three stars are in the region known as DEM L 250. The DSS image of this nebula shows the three stars at the center.

At 48x, the three stars are better viewed very close to each other. NGC 2053 looks, with averted vision, as a small hazy spot of smooth brightness. I got the same view of this open cluster at a little higher magnification (64x), appearing round in shape. At 120x, this cluster looks faint but appears relatively big in the field of this eyepiece. Averted vision improves the view. At this power, the three stars were clearly visible and no nebulosity was glimpsed there.

At 64x, I saw a “star” that looked faint and surrounded by a kind of very small nebulosity, appearing as a defocused star. You can see it does not show the point-like appearance of the stars if you compare it with the nearby (only 2.5 arc minutes away) 9.3 magnitude star HDE 269804. Observing this area with 120x, I could see a very small group of 2 or 3 stars very close to each other. Later, when I checked the DSS image, I identified the three faint stars on the picture (see the small panel on the right hand of Figure 5).

Once again, I am amazed how small details and faint objects can be observed with an 8-inch telescope when they are carefully observed using good charts, deep-sky images (DSS for example), and having a peaceful and dark place to observe from.

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1_ It is situated about 75 miles to the west of Mendoza city, in Los Andes mountains. It is a good place to observe the skies. Geographic coordinates, 32° 36´ 32” S 69° 21´ 18” W.

2_ LHa-120 N- This is the full name of an entry in the Henize catalog 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").

3_ LMC4 is a kpc-sized ring of H II regions in the Large Magellanic Cloud.


4_ 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.

5_ LH is a catalog of OB associations in the Large Magellanic Cloud compiled by Lucke & Hodge.

6_ DEM is a catalog of 357 nebulae in the Large Magellanic Cloud and 167 nebulae in the Small Magellanic Cloud that was published in 1976 by R.D. Davies, K.H. Elliot and J. Meaburn. The LMC catalog is DEM L and the SMC catalog is DEM S.

N11 Complex in LMC

Published in the April 2010 issue of the Rosette Gazette newsletter (Rose City Astronomers, Portland Oregon USA)

The Observation of the Second Largest HII Region

 in the Large Magellanic Cloud

The northwest corner of the Large Magellanic Cloud (LMC) is home of many different kinds of deep-sky objects including bright nebulae, open and globular clusters, and supernova remnants. Several of these objects are visible within the range of average size amateur telescopes.

But more than this, the northwest region hosts the second largest HII region of our satellite galaxy, the N11 complex. I began the observation of this interesting formation from an observing site at Uspallata Valley (Latitude -32.5° Longitude 69.3W 2,000 meters above sea level) at 01:25am (04:25am UT) on February 14, 2010, when the LMC was at 40° high in the sky. This is a circumpolar object at this latitude and it reaches about 53° of altitude when it transits. At the lowest altitude (inferior transit) it is visible at 13° above the South Horizon. Taking this into account, the best season to observe this galaxy is during the southern summer months (December, January, February, & March) when it is high in the sky.

The N11 Complex and Its OB Associations

N11, whose parts are known with the more familiar numbers in the NGC catalog, lies about 4.75° to the northwest of the 30 Doradus complex (Tarantula Nebula) and can be, according to Y. Nazé et. al. in their paper “XMM-Newton Observations of the Giant HII Region N11 in the LMC”, a more evolved version of this latter nebulae. Observing our nearby satellite galaxy through common and average size binoculars (e.g. 10x50) N11 is one of the most prominent features that are clearly visible among others, like the 30 Doradus Complex, the conspicuous off-center bar-type structure (see picture above), and the stellar arcs in the northeast part of the galaxy where Shapley´s Constellation III (one of the most enigmatic structures in the Local Universe: a coherent semicircular arc spanning several hundred parsecs, composed of thousands of bright young stars and tens of star clusters) in the LMC41 region lies. 

I have indicated all these features in the picture above taken by Australian astrophotographers. If you come to the Southern Hemisphere to observe the sky have in mind that N11 is one of the bright extragalactic nebulae to be included in your observing program. The 4.8 magnitude star θ (Theta) Doradus, which is clearly visible to the naked eye from a dark sky site, can be a good starting point to find N11 (see the first picture in this article). This HII region lies about 1.8° west-northwest of this star. 

A first view at low magnification (42x) shows a prominent nebulae complex about 15 arcminutes wide in PA2=234°. It is clearly visible even with direct vision and without a filter, containing some patches with different angular sizes and shapes. As mentioned in the paper above, it harbors some associations2 of massive stars: LH9, LH10, LH13, and LH14 (Lucke & Hodge 1970) and even a supernova remnant, N11L, which is included in another observing project I am carrying out with a bigger mirror (16 inches).

The pattern of three stars indicated with a red circle in Figure 1 helped to find one of the hazy patches in the complex, NGC 1773, the smaller of the three most conspicuous components there. It is situated halfway between the stars HD 32427 (visual magnitude 9.2) and GSC-8889-0432 (visual magnitude 10.7), indicated with letters A and B respectively in Figure 1. You can also use those stars to find it. At this power, NGC 1773 shows a star-like bright center surrounded by a faint and small round nebulosity (see Figure 2). The bright core looks off-center within the nebula. Higher magnification is necessary in order to get a more detailed view of its structure.

An open cluster, NGC 1776, with a magnitude of 13 and about 1 arc minute in size (according to the Wolfgang Steinicke's Revised NGC and IC Catalog) lies close to the star B but I could not see it at this magnification. One of the two brightest patches of the complex, NGC 1769 (indicated in Figure 2) looks round with a symmetric nebulosity surrounding a bright stellar-like core. If you observe this nebula carefully for several minutes, using averted vision, its overall shape is better viewed.

The other brightest nebula, NGC 1763, is also indicated in Figure 2. It is a structure with a brightness similar to that of NGC 1769 and elongated approximately East-West. A more detailed observation at the same magnification (42x) made possible the detection of a stream of faint stars within this hazy structure, the bigger one.

The zone labeled C, which is outlined with a blue line in Figure 1, is visible as several faint stars very close to each other and embedded in faint nebulosity. The brightest part is coincidentally in the area where nebulae NGC 1760 and NGC 1761 are situated in the eyepiece field (in the southwest part of the complex).

After the observation and identification of the whole complex, I decided to use the UHC nebular filter to observe each patch again using the same magnification. NGC 1769 and NGC 1763 appeared smooth in brightness through this filter and more contrasted against the background sky. On the other hand, NGC 1773 looked sharper and the nebulosity in the region labeled C more obvious, with a detached small spot in the south edge, surely NGC 1760.

Using an eyepiece that gives a little higher magnification (78x) two stars appear in NGC 1773 (also N11D) surrounded by a faint nebulosity (see Panel A). Embedded in the nebulosity lies LH 14, the least studied of the four OB associations3.

NGC 1769, at this magnification, shows the star-like core and the surrounding circular nebulosity with more detail. Mentioned above, there are some OB associations in the N11 complex. LH 13 lies in this bright component, also known as N11C. LH 13 contains two compact stellar clusters, Sk−66◦41 and HNT. The ages of the two clusters suggest there is no association between them (Heydari-Malayeri et. al. 2000). I think the stellar core I saw through my 8-inch telescope is actually Sk−66◦41, according to its position in NGC 1769 (see Panel B).

At 78x, the stream of stars in the elongated patch NGC 1763 (also N11B) is clearly visible on its south edge (Panel C). These stars belong to the OB Association LH 10 which is the youngest cluster of the N11 complex containing several O3 stars and, according to Nazé et. al. 2001, is still embedded in its natal cloud but its most massive components have already begun to blow bubbles around them.

Finally, the region indicated with C in Figure 1 looks very interesting at this higher magnification, with several stars easier to observe in hazy background. This group of stars I saw is the LH 9 association (indicated in Figure 1), whose action on its surroundings has triggered a burst of star formation in the periphery leading to the birth of the three other OB associations (Rosado et. al. 1996).

At 106x, using a UHC nebular filter, a very faint and smooth nebulosity with an irregular shape is visible in the zone where NGC 1760 lies (see Figure 1). The view I had of NGC 1760 was not as detailed as shown in the DSS image (Figure 3).

The Surrounding Field of N11

Other objects are situated close to the N11 complex. If we move about 25 arc minutes to the southwest we find the brightest star in the 1° field, HD 31754, a 6.4 visual magnitude reddish star. Very close to it lies the faint (magnitude 13.3) open cluster NGC 1733. I tried to observe it but it was not visible at 42x.

Three galaxies reside to the West of the N11 complex, the pair of PGC galaxies (16243 & 16244) were not visible at low magnification (42x). The same occurred with the galaxy LEDA 89996, not visible even at higher magnification (106x).

To the south of these galaxies lies NGC 1731 (see Figure 1). According to Wolfgang Steinicke's Revised NGC and IC Catalog and software Skymap Pro 6, this is a cluster with nebulosity. Through my 8-inch telescope, it looks like a faint luminosity engulfing the 10.7 magnitude star TYC 8889-619-1, indicated with letter D in Figure 1. The nebula extends toward the direction indicated by the blue arrow there.

Our nearby galaxy is home of several interesting nebulae complexes and group of stars. It is rich in objects to explore through telescopes, thus discovering the wonderful structure and content of this companion, along with the Small Magellanic Cloud, of our Milky Way.

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1_ Nebulae complex to the north of 30 Doradus and to the east of

Theta Doradus).

2_ PA= Position Angle

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.

V633 Cassiopeiae

OBSERVING REPORT

V633 CASSIOPEIAE - HERBIG Ae/Be STAR in Cassiopeia 

HERBIG HARO OBJECTS 161 and 164 in Cassiopeia

Date: September 19, 2014
Time: -
Telescope: 20" (50cm.) f/3.55

Observer: Leo Cavagnaro

   

Click on the image to enlarge

 Finder chart

 How to find it,

 About  0° 25' to the southeast of the 2.3 visual magnitude star Caph (β Cassiopeiae).  

 Stars in map up to visual magnitude 6.0

Herbig Ae/Be stars, first identified by Herbig (1960), are now commonly accepted to be intermediate-mass premain-sequence stars. They are associated with nebulosity and are surrounded by circumstellar material resulting from their formation process. V633 is one of those kinds of stars with the Herbig-Haro objects HH 161 and HH 164 forming parts of the Horseshoe-shaped loop emanating from it. 

At 222x the star V633 Cassiopeiae looks slightly "out of focus" or like a small hazy star. Using averted vision I was able to notice some of faint nebulosity very close, in fact connected with the star to the east. V633 Cassiopeiae along with the Herbig-Haro objects associated with it are easy to find because they lie roughly 25 arc minutes to the southeast of the bright 2.3 magnitude star Caph (β Cassiopeiae), one of the components of the famous constellation Cassiopeia. To the west in the field, the reflection nebula vdB1 engulfs three stars.

At 296x, V633 Cassiopeia looks embedded in a faint nebula, little contrasted against the background sky.

NGC 6334, 6357, & Pismis 24

In the well-known constellation Scorpius lie a lot of conspicuous deep-sky objects. It is not new if we talk about the open cluster NGC 6231, also known as the “Scorpius Jewel Box”, the globular cluster Messier 4, one of the nearest globular clusters to us, or the open clusters Messier 6 (Butterfly cluster) and Messier 7 (Ptolemy´s cluster), both visible to the naked eye. If you want to take a step ahead and observe other objects also situated in this constellation you can, for example, to try to find a couple of nebulae often nicknamed “Cat´s Paw” (NGC 6334) and “War and Peace” (NGC 6357). Within the last one, we found a peculiar open cluster cataloged as Pismis 24, containing interesting massive stars as members.

On July 4, 2009, I had a chance to drive toward the northwest and to reach the Andes mountains with the idea of observing those nebulae. I set up my telescope in a place named Paramillos (latitude –32° longitude 69° W), at 2700 meters above sea level and about 25 km (16 miles) from Uspallata Valley. 

Photo of the constellation Scorpius taken by the author. The white ellipses show the zones where IC 4628 and NGC 6334 & 6357 are situated.

The Southern Hemisphere winter is a good time to observe the region of the sky toward the Milky Way center, with constellations Scorpius and Sagittarius very high in the sky. I made the observations that night under a very clear and steady sky.  On the picture I took, I indicate with a big white ellipse the zone where these nebulae can be founded. You should include these objects in your own observing program if you have in mind to trip to the Southern Hemisphere to explore the southern constellations.

Before observing the two main nebulae in the observing program I aimed my 8-inch telescope to the south region of the constellation (smaller ellipse on the picture above), near the open clusters Collinder 316 and Trumpler 24, both of them part of the Scorpius OB1 association, with the idea of identifying and observe in detail a nebulosity known as “Prawn nebula” (IC 4628).

THE IC 4628 NEBULA

IC 4628 is situated about 1.5 degree North from the well-known cluster NGC 6231 and on the north side of the open cluster Trumpler 24. In fact, several stars in the field are members of this wide and sparse cluster. After identifying the starry field surrounding this nebula I observed it with low magnification (42x). At that moment the nebula was very high in the sky, roughly 79 degrees of altitude. It was visible like an elongated and faint nebulosity in a rich starry field with some stars forming short chains. You can improve the view using a UHC filter. With this kind of filter, the nebula looks wider, more contrasted, and more elongated east-west.

IC 4628 and surrounding deep-sky objects.

A few bright stars are visible surrounding the brighter part of the nebula, outlining it (the only part I can see with my telescope and filters). Fainter stars are visible embedded in the nebulosity.

A more contrasted, round, and small patch is also visible (number 1 on the picture to the left). A bright narrow filament connects that patch with the main part of the nebula. IC 4628 is a big nebula, for that reason it is not a good idea to use high magnifications if you want to observe the whole object, or at least the brighter and more detectable part.

I used an eyepiece that gave me a little higher magnification (53x). Using the UHC filter again the view was still very interesting. Some dark structures were visible in the nebula, especially in its west end. A narrow dark lane seems to cross through the middle of the nebula. Taking the UHC filter off, zone 1 shows a short line of faint stars very close to each other and embedded in a faint nebulosity.

Observing IC 4628 with the same low magnification but this time working with an OIII filter the contrast is maybe a little worse. In my opinion, the UHC filter definitively works better.

According with several deep-sky observers around the world, the H-beta filter works well in a very few objects only, like the California Nebula (NGC 1499) or the Cocoon Nebula (IC 5146). However, it was interesting to use it to observe this emission nebula. I was amazed because, in this case, this filter worked very well. Using low magnification (42x) and this kind of filter the image was very good, with good contrast. Some dark structures within the nebulae were visible also. Beyond the usefulness of the OIII and H-beta, the UHC was the best filter to use at the moment of observing this diffuse nebula.

NGC 6334, THE “CAT´S PAW” NEBULA 

This nebula, also known as “Bear Claw Nebula”, is one of the most prominent sites of massive star formation. The central region consists of a long filament with seven sites of massive star formation. At a distance of about 5500 light-years, it is visible in a rich starry field when you observe it through a telescope. In the same eyepiece field, the dark nebula Barnard 257 (B257) was barely visible at low magnification. The identification of a stellar configuration situated to the West of the dark cloud (to the right on the picture below) helped to find it.

Focusing the attention on NGC 6334, three hazy patches come to the view at low magnification and without any filter. These nebulosities surround stars which are visible within them. Some nebulosity is visible in the area indicated by number 1 in the picture below. To the West (right on the image) there are some very faint stars very close to each other and embedded in faint nebulosity.

The Cat`s Paw Nebula. North is up.

The most conspicuous and bigger nebulosity is that surrounding the star of magnitude 9.4 HD 156738 (number 2 on the image here). The nebula is also visible to the East of the star, always showing a smooth appearance.

The patch indicated by number 3 is also visible without a filter. Between nebulosities 1 and 3, some of nebulosity is detected, embedding the stars situated there. The east end is more contrasted and easier to see visually.

The Observation with UHC filter

This kind of filter allows you to see more contrasted nebulosity in zones 1,2, and 3. The zone in 2 is again the brighter one visible in the field. More structures are visible in this nebula when you use nebular filters. For example, with the UHC filter, you can see the elongated nebulosity marked by the white ellipse in the picture above. I also observed this nebula with an OIII filter but the view was not so sharped and contrasted. Even if the nebulosity 2 is clearly visible through this filter, some other structures begin to fade and they become more difficult to see.

The H-beta filter also works to see this nebula, at least to see its three brighter patches, but it is not the best option when you want to observe NGC 6334. In my opinion, the best filter was the UHC, followed by the OIII filter. H-beta was the last option to choose.

THE NGC 6357 NEBULA & THE OPEN CLUSTER PISMIS 24

DSS image of NGC 6357 and Pismis 24. North is up

About 3 degrees from the bright star Shaula, one of the bright stars in the tail of Scorpius, we found the diffuse emission nebula NGC6357, usually known as “War and Peace nebula”, discovered by John Herschel on June 8, 1837.

The first attempt to see this nebula was using my 8-inch telescope without a nebular filter. After aiming the telescope to that region of the sky, the identification of the surrounding field was easy because there exist four bright stars with magnitudes of 6 and 7 forming a straight line. Actually, they are the brighter stars in the eyepiece field. An open cluster can be found within the nebula, Pismis 24. After having the accurate position of this star cluster among the stars (see comments below) I began with the observation of it and the associated nebula NGC 6357.

There is an interesting story about this open cluster,

NGC 6357 is classified as an emission nebula. The whole nebula was not visible at all. However, the brighter part of it is easily visible even without using a nebular filter. That brighter part, indicated by the red circle in the DSS image above, is better viewed as a small patch of nebulosity, using averted vision. Very close to it, the small open cluster Pismis 24 is clearly visible. According to the software Skymap, this stellar group has a magnitude of 9.6 and its Trumpler classification is IV,2,p,n, thus indicating associated nebulosity. If you use low magnification, you will see a sort of defocused star (the brighter in the cluster) and two fainter stars forming a line with that one. Some very faint stars are visible between that stars and the nebulosity. Using low magnification but this time with a UHC filter, you can get a more detailed view of the nebulosity. This looks better, showing an elongated shape becoming wider toward the direction where the cluster lies. The elongated shape of the nebula is more obvious using a little higher magnification and the same filter.

I used more power (156x) to see the cluster in detail. At this magnification, I could see four stars that remember me a very small version of the constellation Sagitta (The arrow) in the northern sky.

At this magnification I could clearly see the bright star Pismis 24-1 (indicated on the DSS image at the top of this section) and also the star Pismis 24-17 (immediately to the left of Pismis 24-1 on the image). Pismis 24-17 is also a member of the cluster. 

As you can read, awesome nebulosities inhabit the marvelous constellation Scorpius, in the southern skies.