Category: Deepsky observing

Friday, August 14, 2009
NGC 2420 in Gemini


Just a quick update on my new website 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



Posted by Math on 08/14 at 12:18 PM | (0) Comments | filed in: Deepsky observing | Print
Wednesday, June 17, 2009
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
Wednesday, June 10, 2009
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


Image by Dr. Franz Gruber

Posted by Math on 06/10 at 12:30 AM | (0) Comments | filed in: Deepsky observing | Print
Thursday, June 05, 2008
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 ( ). 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
Saturday, July 14, 2007
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.

Posted by Math on 07/14 at 10:54 AM | (0) Comments | filed in: Deepsky observing | Print
Friday, June 09, 2006
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.

Posted by Math on 06/09 at 11:34 AM | (1) Comments | filed in: Deepsky observing | Print
Monday, May 29, 2006
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”.

Posted by Math on 05/29 at 07:42 PM | (0) Comments | filed in: Deepsky observing | Print
Saturday, May 20, 2006
My 20 favorite double and multiple stars, part 3: summer
8. Delta 1 and 2 Lyrae (double star)
Constellation Lyra (Lyre), magnitude 5.6 / 4.2, separation 630”, position angle 243°, RA 18h54m DEC +36°55’. Lyra is, like Bootes and Corona Borealis, a treasure trove for observers of double and multiple stars. Delta 1 and 2 Lyrae are a very wide pair of stars that can be observed with handheld binoculars, and in my 15x80 binoculars (mounted on a mirror mount) I can see a bluish-white delta 1 Lyrae and an orange delta 2 Lyrae surrounded by 10 ten fainter stars, forming a star cluster called Stephenson 1. I love to look at this, 16’ wide, open cluster using my 4-inch refractor. At a magnification of 80x to 100x I see about 15 stars. Delta 1 Lyrae and Delta 2 Lyrae are true physical members of this small open cluster.

Posted by Math on 05/20 at 10:33 AM | (0) Comments | filed in: Deepsky observing | Print
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