Clear Skies On Demand - an astronomy blog

Update on Starobserver.eu

Hi all,

I have to apologize that I have not posted a lot in 2009, but due to some personal things, my time was very limited. I did however put a lot of effort in Starobserver.eu, my new website about observing stars and starclusters. Right now I have documented 24 objects which I have observed in the last year, with sketches and very detailed observing reports: 12 open clusters and 12 stellar objects. In the next few months a hope to add a group of asterisms. Very recently I added a "search engine" to Starobserver.eu and an article about my observing reports. Just have a look at my new site. Any tips and/or comments are of course appreciated.

And here's a sketch of M44 that made it into Astronomy Sketch of the Day:

Anyway, I hope to post a little more in my blog again in the next months.

Clear skies to all of you..........

Posted by Math on 11/30 at 03:27 AM | (0) Comments | filed in: Deepsky observing | Print

NGC 2420 in Gemini

Hi,

Just a quick update on my new website Starobserver.eu. I added another sketch to the open cluster section. Last winter I observed NGC 2420 in Gemini. This little cluster lies in the neighbourhood of the Eskimo Nebula, For a detailed observing report, some info on the discovery of this cluster, a finder chart and other interesting things on NGC 2420, please follow this link to NGC 2420 on StarObserver.eu

Enjoy!

Posted by Math on 08/14 at 12:18 PM | (0) Comments | filed in: Deepsky observing | Print

eta Persei

eta Persei is a bright double star, placed within a striking asterism. When I was writing my notes on this double, I found out the collecting the right data on individual stars is sometimes much more complicated than you think. I got some help from an Austrian astro-photograpeher, Peter Wienerroither. His image of eta Persei was a great help identifying all the components of eta Persei. To read the full report, just follow this link to StarObserver.

Posted by Math on 06/17 at 01:47 AM | (0) Comments | filed in: Deepsky observing | Print

NGC 6910 The Rocking Horse Cluster

NGC 6910, a small and compact open cluster in Cygnus. When observing this open cluster you see bright yellow stars, that are in fact B-stars. So they should appear white. What causes the yellowish appearance is explained in this article, where I got some great help from Professor James Kaler, author of some of the best books on stars, and Dr. Franz Gruber, who sent me a few magnificent deepsky images of the Cygnus area to illustrate the high degree of nebulosity in the Cygnus area. To read the full story, and have a look at the wonderful images of Dr. Franz Gruber, follow this link to StarObserver.eu

Image by Dr. Franz Gruber

Posted by Math on 06/10 at 12:30 AM | (0) Comments | filed in: Deepsky observing | Print

Xi Bootes in Little Cygnus

On the evening of May 9th 2008 Leo and I got together to observe a series of double stars in Bootes, inspired by an article in June's Sky and telescope (Binaries in your Bootes). In the period between the beginning of May and the end of July it doesn't get really dark at night, but for observing double stars or asterisms, this proved to be not a problem at all. We started at 23.00 hours local time (UT + 2hrs). In three hours time we observed and sketched about six doubles in Bootes and two asterisms, one in Bootes (Picot 1), the other in Ursa Major (Ferrero 6).

The highlight for me that night was Xi Bootes. This colorful double lies about 8 degrees east of Arcturus. The Yellow primary star shines at magnitude 4.8 and it's magnitude 7.6 orange companion lies at a position angle of 315°. The separation is 6.3". Through the 17mm Nagler the double looks fairly close (scale from "Double Stars for small Telescopes" by Sissy Haas). When looking at Xi Bootes through the 17mm Nagler, the double seems to be part of an asterism that looks like the constellation Cygnus, only much smaller. Xi Bootes is placed at the position of Deneb, the tail of the swan. We decided to call the asterism "Little Cygnus". On the sketch below the asterism is oriented West-East. At the tail you find Xi Bootes. Three white stars oriented north-south represent the wings of the little swan. A white star to the east (accompanied by a dimmer companion) is at the position of the head of the swan. The yellow star to the eastern edge of the field of view is just a bright field star. It is no part of the "Little Cygnus" asterism.

The sketch of "Little Cygnus " and Xi Bootes was made using the 300mm f/5.3 Dobson and a 17mm Type4 Nagler. The magnification is 94x and the field of view is 52'. At the telescope I made a sketch on white paper using a HB led-pencil. This sketch was scanned and processed in Photoshop. I colored the double star (and the field star to the east) using the tutorial described on the website of Jeremy Perez ( http://www.perezmedia.net/beltofvenus ). This is the first time I experimented with this technique, and I am very pleased with the result. It produces a realistic image and resembles what you see through the eyepiece. In the future I will try to use this technique for sketching more double and multiple stars.

Posted by Math on 06/05 at 09:42 PM | (0) Comments | filed in: Deepsky observing | Print

Observing hidden treasures.........

Last night it was clear between 11 and 1 o clock (local time) and I had a quick look at some deep-sky objects with just to test my new eyepiece, the 21mm Denkmeier. In my dob, the 65-degree eyepiece gives a magnification of 76x and a true field of view of 51'. I pointed the eyepiece at M 27 and although it wasn't really dark (grey nights during the May-July period), it was quite an impressive sight. M 27 is really big, even at low powers, and with the UHC filter the Dumbbell shape is very obvious at first sight. The 21mm Denkmeier seems to be very "transparent", letting through much more light than the 20mm and/or 25mm Vixen Lanthanum. The stars where sharp right to the edges although I think that there is a little pincushion distortion along the edges. What I really love about this eyepiece is the generous 20mm eye-relief. Even with my glasses on, I can take in the whole field of view at once.

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The second object for the night was M 13, the big globular cluster in Hercules. The 21mm showed too much of the grayish sky, but M 13 was already resolved very well. The best view I got with the 7mm Pentax XW (230x). The cluster was completely resolved, even under these mediocre conditions. There were a lot of long streams of stars extending from the bright core. It looked more or less like a big spider. The three dark diverging lanes, which should look like a propeller, stayed invisible again. Probably I need a better seeing and a darker sky for this.

After M 13 I turned the dob toward NGC 6210 (Hidden Treasure 78 from Stephen J. O'Meara's book, Hidden Treasures). Already at the lowest magnification (76x) with the 21mm Denkmeier, this planetary Nebula looks like a deep-blue little disk. Using higher magnifications up to 230x made it look a lot bigger, still blue, but not so blue as with the lowest power. The seeing didn't allow higher magnification, so I could not go for the real details. According to Phil Harrington (The Deep Sky: An Introduction) this planetary takes high magnifications well, and is at its best 150x or more.

I ended my little tour with two objects I had never observed before, Hidden Treasure 94 (The Flying Unicorn Cluster) and Hidden Treasure 18 (The Ghost of the Moon) from the Additional list from O'Meara's latest Deep-Sky Companion. HT94 (NGC6709, Collinder 392), the Flying Unicorn Cluster, is a wonderful open cluster in Aquila. At low powers (78x) the triangular shaped cluster is very obvious, with some very nice groupings of (colored) stars. Although high magnification (230x) revealed more stars, I liked it most in the 12mm Nagler with a magnification of 133x. The cluster was nicely framed, some 40 to 60 stars with some "space" left around it. The colors came out even better than with the low power view, and I could detect quit a few "double-stars" or groupings of several stars; a very nice object, which I will definitely visit again under better conditions.

HT 18 (NGC 6781) from Appendix C (Twenty additional hidden treasures is) is a magnitude 11 planetary, about 2' in diameter. Without filters this big planetary is not so easy to see, but with the UHC filter in place it is a perfectly round, very bright and easy object. There should be some details visible at higher magnification, but because of the bad viewing conditions I did not try this last night, but again a very interesting object, which was completely unknown to me. At the moment this hidden treasure list is my favorite a perfect alternative for those who have done the Messier and Caldwell catalog. I will be back with more observing details on these interesting deep-sky objects, but I will need a darker and more stable sky. Until then, Clear Skies to all of you!

Oh, and the Denkmeier eyepiece is a perfect match for my 300mm f 5.3 dob. If you wear glasses or want a good eye-relief for any other reason, I can highly recommend this relatively small and compact eyepiece.

The Denkmeier 21mm eyepiece compared to the T4 12mm Nagler

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Posted by Math on 07/14 at 10:54 AM | (0) Comments | filed in: Deepsky observing | Print

My 20 favorite double and multiple stars, part 5: winter

17. Rigel (Beta Orionis, Struve 668, double star)
Constellation Orion, also known as the Hunter), magnitude 0.1 / 6.8, separation 9.5”, position angle 202°, RA 05h14m DEC -8°.12’. The primary star, the class B8 supergiant Rigel, is the seventh brightest star in the sky, and it is the brightest star in Orion. In my 8-inch Klevtzov it looks white, but in my 85mm Zeiss reflector, I definitely see a hint of blue. The secondary, using the 8-inch Klevtzov at 166x, also looks bluish-white.

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18. Trapezium (Theta Orionis, multiple star)
Constellation Orion (also known as the Hunter), magnitude AB 6.7 / 7.9 and CD 5.1 / 6.7, separation AB 8.8” and CD 13.4”, position angle AB 31° / CD 241°, RA 05h35m DEC -5°23’. This group of blazing young stars, known as the Trapezium, doesn’t need an introduction. The trapezium is a group of four bright white stars at the heart of the Orion Nebula. Even in my 85mm refractor at 30x I can see them as four individual stars, forming a trapezium. The magnitude 5.1 C component stands out from the other three fainter stars in the 85mm reflector. Under a real dark sky, I have seen the E and F component in my 8-inch TAL 200K using medium to high magnifications. This group of stars is just wonderful through almost every telescope.

19. Beta Monocerotis (triple star)
Constellation Monoceros (Unicorn), magnitude 4.7 / 5.2 / 7.1, separation AB 7.3” and BC 2.8”, position angle AB 132° and BC 106°, RA 06h29m DEC -07°02’. Sir William Herschel discovered Beta Monocerotis in 1781, and called it “one of the most beautiful sights in the heavens”, and I can only agree with him. I have been observing this wonderful triple in Monoceros on every possible occasion, just enjoying the view: three almost equally bright stars with the same blue-white color. The A, B and C component form a narrow triangle, and I never found another group of three stars that are so close together, equally bright and of exactly the same color. With my 8-inch telescope I use a magnification of 166x to get a real nice split.

20. Castor (Alpha Geminorum, Struve 1110, triple star)
Constellation Gemini (Twins), magnitude 1.9 / 2.9 / 8.8, separation AB 4.0” and AC 72.5” , position angle AB 68° and AC 164°, RA 07h34m DEC +31°53’. In fact, Castor is a system of six stars. Three of them are visible through amateur telescopes, the A,B and C components. Each of the three visible stars is itself a spectroscopic binary. The faint c-component is in fact a pair of red dwarfs orbiting each other, an eclipsing binary (variable star) designated YY Geminorum. Through my 8-inch telescope at 200x all three components look white.

Image from SkyTools2 by CapellaSoft, click to enlarge!

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Posted by Math on 06/09 at 11:34 AM | (1) Comments | filed in: Deepsky observing | Print

My 20 favorite double and multiple stars, part 4: autumn

13. Eta Cassiopeia (S)truve 60, double star)
Constellation Cassiopeia, magnitude 3.4 / 7.5, separation 12.9”, position angle 317°. RA 00h49m DEC +57°49’. This beautiful double was discovered first by William Herschel in 1779. At the moment, both components of Eta Cassiopeiae are separated 12.9”. Calculations based on observations show that the separation varies from 5” (in 1890) to approximately 16” in 2150. The period of the apparent orbit is somewhere between 480 and 520 years. In different observing reports the colors of both components are reported as gold or yellow for the primary and orange or red for the secondary. I only observed it once, under mediocre circumstances, with the 8-inch Klevtzov-Cassegrain. To me they both looked “golden”.

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Posted by Math on 05/29 at 07:42 PM | (0) Comments | filed in: Deepsky observing | Print

Category: Deepsky observing