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
Tuesday, May 09, 2006
My 20 favorite double and multiple stars, part 2: late spring – early summer
5. Polaris (Alpha Ursa Minoris, the North Star, the Pole Star, double star)
Constellation Ursa Minor, (Little Bear), magnitude 2.0 / 8.2, separation 18.4”, position angle 218°, RA 02h32m DEC +89°16’. This star is without question one of the best-known stars in the sky, but I wonder how many people know that Polaris is also a very nice double star. Through my 8-inch TAL at 133x, the primary looks yellow and the much fainter secondary looks white. Use medium to high magnification (at least 100X) to split the faint secondary from the bright primary. At low magnifications the secondary is lost in the glare of the primary. If you have an equatorial mount, you might find it difficult to get Polaris into view. You should polar align your mount exactly, or simply turn your polar axis about 90 degrees to the east or west, using your mount more or less as an alt-azimuth mount, and it shouldn’t be too difficult to get Polaris in the centre or the eyepiece. I use the exact polar align method.

Posted by Math on 05/09 at 07:25 PM | (3) Comments | filed in: Deepsky observing | Print
Sunday, April 30, 2006
My 20 favorite double and multiple stars, part 1: early spring
During the last few years I “re-discovered” a group of objects that is not as badly affected by light- and air pollution as other deepsky objects: double and multiple stars. Many hundreds if not thousands can be observed from my own suburban backyard, and almost every time I point my telescope on a double or multiple star for the first time, I am in for a big surprise. There are a lot of different factors that can turn a double or multiple star into a true celestial gem. Their components often have beautiful contrasting colors or they show a huge difference in the magnitude. But also a very close couple or group of stars of the same color and/or almost equal magnitude can look simply stunning.

There is no way to catch the telescopic views of double and multiple stars on a photograph, without destroying the aesthetic beauty of these truly sparkling stellar gems. On photographs stars turn into more or less disk-shaped blurry blobs of light. Gone are the sparkling colors, the point-like star-images and the stunning differences in magnitudes. So no matter where you live, whether in the city, somewhere in the suburbs or in a rural area, go out and observe them with your own eyes, using binoculars or a telescope. Only then you will “see” the real beauty that this often neglected group of deepsky objects has to offer.
Posted by Math on 04/30 at 10:06 AM | (5) Comments | filed in: Deepsky observing | Print
Monday, March 27, 2006
Double rainbow
Just after dinner we saw a double rainbow right above the street where we live. I rushed outside to find the pot of gold at the end of the rainbow, but once I was outdoors, I decided that the view was too beautiful to be ignored. I quickly grabbed my camera and shot a few images and after that, I simply enjoyed the view. The new telescope will have to wait a littlle longer (sigh).

image image
Click to enlarge!
Posted by Math on 03/27 at 02:12 PM | (0) Comments | filed in: Atmospheric optics | Print
Friday, March 24, 2006
Lunar fact sheet
In the last few weeks I collected some basic lunar data from different online resources and books. I allways find it handy to have this kind of related data grouped together. Click on the image below to enlarge. Of course you are free to download and print the fact sheet. Just click on this link to download the PDF.


Click to enlarge

Posted by Math on 03/24 at 05:41 AM | (0) Comments | filed in: Lunar basics | Print
Thursday, March 23, 2006
Searching this blog, posting comments and register for my newsletter
I just had my blog updated by Mel from "emtwo webstudios". There were a few minor (security) problems with the blog, and I'm glad that they everything is working fine again. Maybe this is the good time to tell you how to search my blog and how to post comments, because both features have been updated. At the end of the article you will find how to register for my newsletter.

Searching items in Clear Skies On Demand
There are three ways to search certain items in my blog. All three options can be found in the sidebar of the blog: Categories, Archives and Search. I will try to explain the differences between the different search methods.
Posted by Math on 03/23 at 05:30 PM | (0) Comments | filed in: About this blog | Print
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