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HTT-Skyguide 2012   -   part 3:  Deep Sky / Overview
  Information  CZ / E / D

Observation Tips  +  finder charts

The milky way at Jessnig's sky. The sky was slightly brightened because of the summer twilight (July 15th). For photographing we used a reducer which gave a focal lenght of 9 mm at our Canon camera. So we could shot a large area of the sky and the milky way at once.

The constellation Swan is a rich source of deep sky objects. This image, for which we also an invertierted version, shows all the stars necessary for finding many of the show pieces. This photograph shows clearly the region around the North America nebula and the Cirrus nebula. Many objects can be found in the center of the Cygnus. These are referenced in the folloowing map:

comparision photograph - map... The map was created with the help of the Uranometria 2000.0 by Andreas Schnabel.

Deep sky observers should take a special look at the region around gamma Cygni with the Gammy Cygni nebula IC 1318 and other H alpha regions. We recommed the use of nebula filters at very good observing sites. The visual observation is not easy because of the lots of faint milky way stars, which may shine out the dim nebulae. Our eyes are less sensitive for the red color of the most nebulae.
                              If you don't like to search for such hard core object you may simply wander through the Cygnus-Aquila-Scutum region. There you can bath your eyes in lots of stars.

There are different opionons about the 'real' Northern coalsack. We believe that only the region to the north of NGC 7000 can get this attribute. Other astronomers came to the same result, e.g. Dr.Paul Ahnert, Rudolf Brandt, Bernd Mueller, Eberhard Splittgerber and Ronald Stoyan. The dark region around Gamma Cygni is much les opaque. This can be seen easily under a real dark sky. If you know the real (southern) coalsack, you know how dark it ist. Only the region between the North America nebula and the Cephes region is of comparable darkness. To illustrate this we show two photographs: A 120 years old image under the very dark sky to this time and a new one, which was made at the 10th HTT.
The summer milky way: Two images in a historical comparision

The comparision of Wolf's photopraphs with contemporary images "Made in Southern Brandenburg" shows that you don't see the technical abilities of our photographers, but the outstanding quality of the sky at our observing site. Ouside of the Alpes you find such conditions in some regions in Poland, the Czech republic, Croatia and Mecklenburg. You see not only the bright star clouds of the Milky way but subtle dust filaments. Look for these especially in the bottom third of the image.
[for more information: here and here].

Click at the image for a larger version with more information.

Let's now look at a real large area of the sky, the Great rift. It starts in the heart of Cygnus and divides the Milky way in two parts. During it's course to the horizon it gets wider. We see here a giant dark nebula, the dark band of our own galaxis. An outer view would give an apparition like the one at edge on galaxies - e.g.
NGC 3628 in the triplett in Leo.
If you collect more light by longer exposition time you see that the great riff is not complete black. The dust cloud are lightened by embedded stars. Large areas which are really black are both of coalsacks - the southern in the near of the Southern cross and the northern between Cygnus and Cepheus. Please look at these photogrphs with different exposure times:

       Great Rift (with intermediates exposure time): Dust areas are still black.   © Ralf Hofner.

       Enhanced exposition: Some of the dark areas show brightness, mostly in brown hues.   © Michael Möckel.

       Cutting from the image at the top of the page. Using maximal exposure time the bright star clouds start to burn out and the dark rift changes in light brown star
       clouds with much of young stars in it.   © Ralf Hofner

It is interesting to see that the dark areas which are in front of the inner part of the Galaxy remain black. You can see this effect at the Northern coalsack and at B168 near the Cocoon nebula. Here we see that the region norther of NGC 7000 deserves the name "northern coalsack" most. It is the darkest region in the northern milky way.
The Great rift can be seen best with naked eye. The different degrees of opacity can be seen if the real is very transparent with very less additional light.
Please pay atention to the other links to the HTT 2012 skyguide:
Planets, asteroids, comets
Zodiacal light bridge + morning sky
DEEP SKY 2 (Details)                                                                        ... And here back to Skyguide Overview 2012.
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