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26th / 27th of September 2003: Observing session at Emberger Alm, Austria, ITT 2003


(Objects observed M16, M17, M18, M24, M22, M8, M11, IC 4756 and NGC 6633, NGC 253, NGC 247, NGC 188, NGC 891)


I started my observing session on Friday the 26th of September 2003 at the Emberger Alm in Austria (46.46N 13.12E) at 19.30 UT. The sky was very clear in all directions except for the lower parts in the south. The visual magnitude was between 5.7 and 5.8. The milky was visible overhead, spanning the sky from the east to the west. Parts of the milky way like NGC 7000 (The North America Nebula) and the Scutum star cloud were visible to the naked eye. Sagittarius was already deep in the southwest. When I turned my telescope into this direction I immediatly noticed several fuzzy blobs in my 7° viewfinder. I decided to give it a try.

Below you will find a map giving an overview of the area I visited first, with the Messier objects you can find in this part of the sky.


Sagittarius

Credit and © Software Bisque, “TheSky for Macintosh”


M16 (Eagle Nebula and star cluster)


The first object I centred into my eyepiece proved to be M16 in Serpens Cauda, a large star cluster (NGC 6611) and emission nebula (IC 4703), The Eagle Nebula. This nebula is also known as “The Ghost” (O'Meara) and “The Star Queen Nebula” (Burnham). M16 lies at a distance of 6.500 light years in the Sagittarius-Carina spiral arm. In my 32mm eyepiece with a true field of view of 46′, the cluster and the nebulosity lie at the end of an S-shaped asterism of stars, which can be identified easily. The open cluster has a diameter of approximately 20′, and has a visual magnitude of 6.0. Its brightest star has a magnitude of 8.2.

M16

Credit and © Software Bisque, “TheSky for Macintosh”


The Eagle Nebula can be found in the northern half of the S-shaped asterism (see image above, South is up. West is to the left, red circle is FOV 32mm Televue Plossl) . It can be detected without a filter, but an O-III filter enhances the view. M16 is very well known since the famous image the Hubble Space Telescope took from its centre, “The Pillars of Creation”, where star formation is occurring. Through my telescope the eagle-shaped nebula could be detected very easily, using the OIII filter. The nebula is about 120′x 25′ but I could only detect the central part, an area of 10′x 15′ at maximum.


M17 (Omega or Swan Nebula and open cluster)


Only 2° to the southeast of M16, I found M17, a vast H II region in Sagittarius. Like in M16, star formation occurs in this region. M17 is visible as a small hazy patch of light in my 8 x 50 finder scope. This beautiful object, a combination of an emission nebula (NGC 6618) and open cluster (also NGC 6618), was discovered by Chesaux in the spring of 1746, before it was rediscovered by Messier in June of the same year.

M17 lies at a distance of approximately 5000 light years. It's a very bright nebula, measuring 20′x 15′. Except for M42, M17 is the brightest galactic nebula visible on the northern hemisphere. Again the OIII filter brings out the details. It looks like a big number “2” or like a swan. There is a big rectangular bar with a sort of hook at the end. When I put the nebula on the edge of the field of view, and switch of the telescope's clock-drive, it looks like a big white swan drifting through the eyepiece. This object shows almost as much detail as M42, the Great Orion Nebula. It takes medium and high magnifications very well. The black and white image below should give you an idea of what M17 looks like through the eyepiece. It comes very close to what I have seen. South is up, West is to the left.


M17

Credit and © William C. Keel


M18 (O' Meara's Black Swan)


This small (and often neglected) open cluster can be found 2° south of M17 and 2° north of M24, the Small Sagittarius Star Cloud. It was discovered by Messier in 1764. M18 is a galactic cluster of magnitude 6.9. It's diameter is 5′ and it lies at a distance of 4.000 light years. With my 12mm eyepiece (166x, True FOV 12′) I counted 20 to 25 stars in M18.

As O' Meara describes in his book “The Messier Objects”, the outline of M18 indeed looks like a “Black Swan”.


M18

Credit and © Software Bisque, “TheSky for Macintosh”


On the image above (South is up, West is to the left, red circle is FOV 12mm Vixen Lanthanum) you see the swans “neck” on the left, and on the right you see the big black “wing” of the swan. So here we have a black swan (M18) and a white swan (M17) just 2° apart from each other.


M24 (The Small Sagittarius Star Cloud)


Our own solar system lies at the inner edge of the Orion Spiral Arm. When we look into the direction of Sagittarius, we are looking in the direction of our galaxy's centre. Across the interarm void we see the Sagittarius-Carina Spiral arm, which is rich in open clusters and nebula like M8, M17 and M20. Through a window in the Sagittarius-Carina Arm we see M24, a section of the Norma Spiral Arm, a far interior spiral arm of our galaxy. Just over the Sagittarius-Carina arm you find the Great Sagittarius Star Cloud, a part of the galactic hub itself.

M24, a section of the Norma Spiral Arm, lies 2° south of M18. When I looked through my 32mm eyepiece (True FOV 46′) I immediately noticed that this object is far too big for my telescope. It measures about 1 x 2° (eight full moon's!!), an ideal object for rich field telescopes and big binoculars. But still it is an impressive sight, when you consider looking at a part of the Milky Way, lying at a distance of 9.500 light years away from us. There are hundreds of bright stars to be seen, embedded in a glow of unresolved background stars. I'm waiting for my new big binoculars, so next time I hope to observe M24 as one big object instead of observing only parts of it.


M22


Next stop was M22, a globular cluster. It lies about 2° north east of 22 Lambda Sagittarius (Kaus Borealis). In my finder scope it looked like a real big fuzzy patch of light. The first view through my 32mm eyepiece knocked my socks off! M22 is a really big globular cluster. The biggest I have observed until now. It filled more than one third of the field of view, about 17′. It's full diameter (as seen only on photographs) is 32′. M22 is the fourth biggest and third brightest globular cluster, as you can see in the table below:


Name Constellation Diameter Magnitude
NGC 5139 (Omega Centauri, Caldwell 80) Centaurus 55′ 3.7
NGC 104 (47 Tucanae, Caldwell 106) Tucana 50′ 3.95
NGC 6121 (M4) Scorpius 35′ 5.4
NGC 6656 (M22, Great Sagittarius cluster) Sagittarius 33′ 5.2
NGC 6397 (Caldwell 86) Ara 31′ 5.3
NGC 6752 (Caldwell 93) Pavo 29&prime 5.3
NGC 5904 (M5) Serpens Caput 22′ 5.7

I tried different magnifications, but the view through the 32mm was the most spectacular. M22 is even better than M13. I could not resolve the core in my 8-inch telescope, but the halo showed a lot of well-resolved stars. This object will definitely be on my observing list the next time I visit a more southern observing location again.


M8 (The Lagoon Nebula and open cluster)


My last stop in Sagittarius was M8. The emission nebula (NGC 6523) and the open cluster (NGC 6530) lie about 8° west of M22. With the help of the OIII filter, the lagoon nebula was impressive, and easy to observe. The nebula is very big (90′x 40′) but I could only detect the centre. I did not examine the open cluster. Because of the fact that M8 was very low in the sky at the moment of observing, I did not stay with it too long. I left Sagittarius and started observing objects a little higher in the night sky.



M11 (The wild duck cluster)


This open cluster in Scutum is very easy to locate. I always start at 17 Zeta Aquilae. From there I go south for 18° in a straight line. When moving my telescope in the southern direction, I always keep looking in my 7° finder scope until I notice a more or less half circle of bright stars: 14, 15, 16 and 12 Aquilae (see image below, South is up, west is to the left, the red circle is the 7° FOV finder scope). I then prolong the imaginary half circle along 12 Aquilae into Scutum. At the end of this extended line I find M11, the Wild Duck Cluster.


M11

Credit and © Software Bisque, “TheSky for Macintosh”


M11 is one of the richest and brightest open clusters. It has a magnitude of 5.8 and contains about 500 stars brighter than magnitude 14; its diameter is about 13′. In the finder scope and at low power magnifications, M11 looks like a globular cluster, but when you increase magnification, the cluster starts to resolve into individual stars. In my telescope at 133x M11 looks round, but when you look more carefully, you can detect a more or less triangular shape. That's probably the reason why admiral Smyth called M11 the Wild Duck Cluster. The form resembles a flight of wild ducks. In the centre shines a lonely star of the 8th magnitude. At 166 times I can see about 150 stars, grouped in clumps and strings, with dark lanes meandering through the cluster. With increasing magnification more stars become visible. M11 should be on everyone's list of favourite deep sky objects.


IC 4756 and NGC 6633


It is about 22.00 hrs UT when I take my first brake from the telescope. After a few minutes I got out my binoculars. I took a final look at M11, before sweeping the night sky with it. About 10° north of M11 I found two small groupings of stars with my 7 x 50 binoculars. I switched to my friends Vixen binoculars (12 x 80) with a TFOV of 4.5°. They showed two bright clusters of stars in the same field of view. I checked my star map, and it proved to be IC 4756 in Serpens Cauda and NGC 6633 in Ophiuchus. This was the first time I observed these two objects. They are ideal for observing with big binoculars. The map below should give you an idea what you see in a 7 x 50 binocular (North is up. East is to the left). The limiting magnitude is about 9 to 9.5 and the big red circle represent a field of view of 6.1°. IC 4756 is on the left and NGC 6633 is on the right.


IC 4756 and NGC 6633

Credit and © Capella Soft, “SkyTools2”


IC 4756 is the bigger of the two. It has a diameter of 52&prime. It contains about 80 stars ranging from the 8th to 11th magnitude. About 3° to the northwest, just over the border of Ophiuchus, lies NGC 6633. This open cluster is smaller than IC 4756. NGC 6633 has a diameter of 27′ and contains some twenty stars from magnitude 7 and fainter. Two very interesting open clusters which look very different.


NGC 253 (The Great Sculptor Galaxy, Caldwell 65) and NGC 247 (Caldwell 62)


After observing IC 4756 and NGC 6633 I turned my binoculars in the direction of the constellation Sculptor. I was looking for NGC 253 (Collinder 65), the Great Sculptor Galaxy, which was discovered by Caroline Herschell, the sister of William Herschell, in 1783. She discovered NGC 253 from the south of England, at 51.3 Northern Latitude (Datchet near Windsor Castle). I live at latitude of 50.5 North, but the obstructed views and the severe air- and light-pollution make it impossible for me to locate an object that comes only a few degrees above the horizon. So I decided to give it a try in Austria, at latitude of 46°.

I took Diphda, or 11 beta Ceti in Cetus as a starting point. This star is also known as Deneb Kaitos, from the Arabian “Al Dhanab al Kaitos al Janubiyy”, the “Tail of the Whale towards the South”. NGC 253 can be found about 7 to 8° to the south of this 2nd magnitude star. When I scanned the area with my 7 x 50 I immediately detected NGC 253 as a faint smudge of light. I switched to the telescope and within seconds the galaxy was centred in my 8 x 50 finder scope. I put my 32mm eyepiece into the diagonal and there it was! Although the southern horizon looked like “milk”, and there where only a few stars visible due to the moist air in this direction of the sky, it was a spectacular sight. NGC 253 is 30′x 7′, with a visual magnitude of 7.6 and a surface brightness of 13.2.

In my eyepiece it seemed to be 20′x 5′(approximately). There where definitely some dark and bright areas visible. I also saw two bright stars to the southwest of the centre of the galaxy. With averted vision I could detect one or two foreground stars, superimposed on the outer edges of NGC 253. A breath-taking view!


NGC 253, Great sculptor galaxy

Credit and © Software Bisque, “TheSky for Macintosh”


In my star atlas I noted that between NGC 253 and Deneb Kaitos there is another big galaxy situated, NGC 247 (Collinder 62). This galaxy, like NGC 253, also belongs to the Sculptor Galaxy group, the closest group of galaxies to our own local group. NGC 247 is very easy to locate. I moved my telescope about 5° to the North, in the direction of Deneb Kaitos. While moving the telescope, I kept looking through the finder-scope. NGC 247 showed up at the position the star atlas indicated, 3° south-southeast of Deneb Kaitos. This galaxy, which lies within the borders of the constellation of Cetus, is 20′x 6′and has a visual magnitude of 9.2. Its surface brightness is 14.1.

In my telescope NGC 247 looked faint, about 10′x 2′. It is oriented north south, while NGC 253 is oriented northeast to southwest. There is a star visible at the southern tip. I could not detect any details.


NGC 188 (Caldwell 1)


In my own backyard buildings and trees, especially in the Northern direction, obstruct the view. There is an open cluster, NGC 188 that lies only 4° from Polaris, in the constellation of Cepheus. So again, this was the place to give it a try. The cluster is 15′; in diameter and contains 120 stars, but in an 8-inch telescope you can only see about 10 to 12 stars of the 12th and 13th magnitude.

It was a hell of a job to point my telescope with its equatorial mount in the right direction. The closer you get to the north celestial pole, the harder it gets! After fiddling around for ten to fifteen minutes, I finally found NGC 188. It wasn’t a real spectacular sight, but still I managed to get it into the telescopes field of view. NGC 188, a very old open cluster (estimated 5 billion years old), showed only 10 to 20 faint stars. I could not detect the glow of unresolved stars.


NGC 891 (Caldwell 23)


From there I went to another region that is hard to navigate, the zenith. I was going for NGC 891, an edge-on galaxy in Andromeda. It was around 01.00 hours UT and Andromeda was right above me in, in the zenith. To find NGC 891, you have to locate two objects, M34 (open cluster) in Perseus and the yellow-blue double star Gamma Andromedae. With my viewfinder, that has a TFOV of 7°, this was fairly easy. Both objects fitted in one field of view. They are separated by a little more than 6°. NGC 891 lies halfway between M34 and Gamma Andromedae. I centred the finder-scope in a sort of trapezoid, formed by four stars (magnitude 6 to 7). NGC 891 lies inside this trapezoid, just to the northwest of the most eastern star (on the image below, South is up and West is to the Left).


NGC 891

Credit and © Software Bisque, "TheSky for Macintosh"


On the night before I had looked for NGC 891 for more than an hour, but I could not detect it. Tonight I had a little more luck. I immediately detected a sort of silver needle, about 10′long and maybe just 1.5′to 2′wide. This object is not as easy to detect, as I thought it would be. In my own backyard I only once got just a glimpse of it. Its magnitude is 9.9 and its surface brightness is 13.7. The dust lane is absolutely not visible. But still NGC 891 was a very satisfying object to end my long night of observing with. Most of the time NGC 891 is invisible in my suburban backyard.

At 02.00 hours UT, after more than 6 hours of observing, I packed up my telescope. It had been a very rewarding night.





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