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9. the Double Double (Epsilon 1, and 2 Lyrae, quadruple star)
Constellation Lyra (Lyre), magnitude AB 5.4 / 6.5 and CD 5.1 / 5.3, separation AB 2.6” and CD 2.3”, position angle AB 357° and CD 94°, RA 18h44m DEC +39°40’. The Double Double was the first double/multiple star system I observed with my 8-inch Klevtzov in 2001, and until now the views I got that particular night were the best I ever got from this celestial gem. It was late in august and it had been a very hot and humid day. Around midnight, the outdoor temperature was still above 20 degrees Celsius. There was absolutely no wind and during the daytime, the sky had looked milky-white. During the evening, the air felt heavy and around midnight, the night-sky looked hazy, somehow covered in high cirrus clouds. It seemed useless to get the equipment out for observing, but I just got my new telescope and I couldn’t wait to give it a try. When I pointed the 8-inch TAL at the Double Double, I was stunned by the view. At 166x I saw four bright white stars, of almost equal magnitude, grouped in pairs, two by two. The image looked like the stars where frozen in their position. There was absolutely no movement, no shimmering stars. Both doubles were split perfectly. Later I realized that for observing close double stars, the conditions must have been nearly perfect that night. I observed the Double Double again and again over the last few years, but I never managed to get the same wonderful views I got on that hot night in august 2001.

10. Albireo (Beta Cygni, double star)
Constellation Cygnus (Swan), magnitude 3.1 / 5.1, separation 34”, position angle 54°, RA 19h31m DEC 27°58’. In 1978 I followed a course “Astronomy for beginners” at the local astronomy club. The course started in the last week of august and after every lesson, we would go outdoors and look at a few objects through a 4.5-inch reflector. I remember looking at the Andromeda Galaxy, the Double Cluster in Perseus, M13 and ………. Albireo. Until then I had never seen a double star through a telescope, let alone a colored double star! Ever since, I have been looking at Albireo on every possible occasion, with all binoculars and telescopes I ever owned, and I still love to observe this simply beautiful object, even after all these years. Through my 8-inch at 66x the primary, a type-K star, looks golden or yellow. The secondary, a type-B star, looks blue. The contrast, color and brightness of both stars is striking, and this magical double star should be at the top of everyone’s observing list. It is one of the easiest doubles to find and, for me personally, the most beautiful to look at.

11. Omicron 1 and 2 Cygni (31 and 32 Cygni, multiple star for binoculars)
Constellation Cynus (Swan), magnitude 3.9 / 3.9, separation 1°, RA 13h6m DEC +46°44’ (coordinates for Omicron 1). Now this is my favorite multiple star (or group of stars) for binoculars. Through my 15x80, Omicron 1 and 2 Cygni look like two bright orange stars, separated about 1° from each other and of almost equal magnitude. Omicron 1 (31) Cygni is a visual triple itself. About 5’ to 6’ away to the northwest of the orange primary, at a position angle of 323°, I see a bluish (magnitude 4.8) companion and about 100” to the south I see a white (magnitude 6) star at a position angle of 173°. Together, Omicron 1 and 2 Cygni form a wonderful group of four stars to observe with binoculars.

12. 61 Cygni (Struve 2758, double star)
Constellation Cygnus (Swan), magnitude 5.2 / 6.1, separation 30”, position angle 150°, RA 21h07m DEC +38°45’. This is a wide double, which can be separated even in small telescopes and binoculars. Because of their more or less equal brightness, I managed to split 61 Cygni with my 7x50 Bresser mounted on a mirror mount. I never managed to split Albireo in my 7x50, although the angular separation of Albireo is wider (34”), than from 61 Cygni. This is probably caused by the magnitude difference. While Albireo’s components differ about two magnitudes, the brighter A component overpowering the fainter B component, the difference between the 61 Cygni components is only 0.8 magnitude, making it easier to “see” both the primary and secondary as separate stars at low powers. In my 15x80 both the primary and secondary of 61 Cygni look chrome-orange, with a hint of red. Again another celestial gem that shouldn’t be missed!



Image from SkyTools2 by Capellasoft, click to enlarge!
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6. Epsilon Boötis (Struve 1877, Mirak or Izar, double star)
Constellation Bootes (Herdsman), magnitude 2.9 / 4.9, separation 2.8”, position angle 339°, RA 14h45m DEC +27°04’. In Bootes and the neighboring constellation Corona Borealis I observed quite a few double stars, but Epsilon Boötis, nicknamed Pulcherrima (in Latin: the beautiful) by F. Struve in 1829, is definitely my favorite. Through my 8-inch TAL at 166x this wonderful double has a bright yellow primary and the secondary is white with a slight hint of blue or green. I cannot decide on the color of the secondary. Which color do you see?

7. Ras Algethi (Alpha Herculis, double star)
Constellation Hercules, magnitude 3.5 / 5.4, separation 4.7”, position angle 107°, RA 17h15m DEC +14°23’. This beautiful double in the lower right part of Herculis is again a really good example of the simple beauty of double stars. Through my 8-inch TAL at 133x the primary is orange and the secondary looks white with a hint of green. Now, I know that there are no “green stars”, but it’s just the way the secondary of Alpha Herculis looks to me through the eyepiece. Color perception depends on a lot of different factors, the contrasting colors of stars being one of them. But also the equipment, the local seeing, and last but not least the observer, and the condition he is in, have an influence on color perception. I noticed during star parties and observing sessions with other observers from the local astronomy club, that observing star colors is a very subjective, personal matter. What looks green to one person looks blue to the other. You get the same discussion with yellowish stars. Some see them just as plain white, others as yellow, golden or orange, and some even see them as red.

I can only give you the advice to record the colors what you observed yourself, no matter what others claim to “see” . Write down your own perception in your observing log. Again, seeing colors is a very subjective thing. You best remember your observation, if you write down what you saw, not what others tell you they saw.



Image from SkyTools2 by CapellaSoft, click to enlarge!

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Anyway, I always have been a visual observer of the deepsky, and I just love these little gems for their aesthetic beauty. So here is my personal top 20 of double and multiple stars (until now), including basic data (constellation, magnitude of all components, separation, position angle, the RA/DEC (right ascension / declination coordinates), some background information, what to expect at the telescope and or binoculars, and of course finder charts for all 20 stars.

I present my 20 favorite double / multiple stars in five consecutive articles, for every time of the year a separate one, starting with early spring constellations and ending with winter constellations. The articles will be published in this blog within the next 6 weeks, starting today. So if you are interested in observing some wonderful double and multiple stars, hop in every now and again to read or print out the series of articles. With this first article, you can start observing double and multiple stars tonight. Clear skies!

My 20 favorite double stars part 1: early spring

1. Iota 1 Cancri (Struve 1268, double star)
Constellation Cancer (Crab), magnitude 4.2 / 6.6, separation 30.5”, position angle 307°, RA 08h54m DEC +28°46’. Cancer is a very faint constellation, but it holds some great open clusters and double stars. Most of you will know M 44, the beehive cluster and M 67, another fine open cluster in Cancer. But at the northern end of the crabs figure you can find iota Cancri, my favorite object in this barely noticeable constellation. Iota Cancri is a magical double, and it could easily be called the “Albireo” of spring. In my 8-inch at 100x it is an striking golden-blue pair of stars. Wonderful! A hidden treasure of the night sky that should be on everyone’s deepsky observing list.

2. Algieba (Gamma Leonis, Struve 1424, double star)
Constellation Leo (Lion), magnitude 2.2 / 3.5, separation 4.4”, position angle 127°, RA 10h20m DEC +19°51’. The name of this star could be from the Arabic “Al Jabha”, the forehead or from the latin word “iuba(e)”, the manes (of the lion). Algieba is the brightest star in the lion’s mane. It consists of a very close pair of stars, but I split the double at 133x with an 8-inch telescope easily. Both the primary and secondary look yellow to me. If you have a small telescope and find it difficult to split this close double, try it in twilight or with moonlight. This often seems to help with splitting bright close pairs, because the glare of the star is reduced. I even read a report from a German observer who got the best results by observing Algieba in a clear blue autumn sky in broad daylight, using a 63mm telescope. To be honest, the only star I ever saw in daylight was the Sun, so maybe I should give it a try.

3. Cor Caroli (Alpha Canum Venaticorum, Struve 1692)
Constellation Canis Venatici (Hunting Dogs) magnitude 2.9 / 5.5, separation 19.4”, position angle 229°, RA 12h56m DEC +38°19’. Cor Caroli, the Heart of Charles, marks the position of one of the two hunting dogs, Chara. Beta Canum Venaticorum marks the other dog, Asterion. Cor Caroli is a fine double and very easy to split in small telescopes. In my 4-inch refractor (TAL) at 83x I definitely see two white stars of unequal brightness. Others report two yellowish stars. Which colors do you see? If you’re not sure, turn the focuser slightly until the stars are out of focus, looking more or less like disks, making color detection easier.

4. Mizar and Alcor (79 Zeta Ursae Majoris and 80 Ursae Majoris, double star)
Constellation Ursa Major (Great Bear) magnitude 2.4 / 4.0, separation 708”, position angle 71°, RA 13h24m DEC +54°56’. Alcor and Mizar both can be seen with the naked eye from my suburban backyard, and it was the first double I pointed my very first telescope (a 4.5 inch reflector) at in 1978. In this small telescope, Alcor and Mizar were both separated widely and placed in the opposite ends of the field of view, and to my surprise Mizar was a double star itself. Mizar’s secondary with a magnitude of 3.9, can be seen at a position angle of 150° and the separation between Mizar A and B is 14.4”. To me, Alcor, Mizar A and B all appear to be white.


Image from SkyTools2 by CapellaSoft, click to enlarge!


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Categories
You can browse through the categories and subcategories the same way you would browse through a directory structure on a hard drive. For instance, if you want to read about my solar observing sessions, just click on the subcategory “Solar log" in the category “Sun". All articles with solar observing reports will appear in the main window on the right. They will appear sorted by date. The newest entry is always at the top, the oldest at the bottom of the last page.

Archives
You can browse all entries that are in the blog, by browsing through the archives. All entries are in a SQL database, and you can browse through them by date or by category. Just click on “Monthly Archive Listing" or “Category Archive Listing" and a list will appear, with all article titles sorted by date, or by category. I personally use the Category Archive Listing a lot. It shows all the entries per Category, listed alphabetically.

Search
This is the most powerful option to find a certain item you are looking for. Simply type in the text, for instance Copernicus or Herschel, and all entries in which this word is used will appear in a list with the title, the first lines of text of the entry and the author and date. You can go the article you want to read by clicking on the title. The search option really searches the complete database, and if a word is used somewhere in this blog, the entry will appear in the listing. If you get too much search results, narrow down your search by clicking on “Advanced Search" beneath the search window.

Posting comments
This option has been corrupted (some security issue) during the last few months, but thanks to Mel it works just fine again. How can you post a comment?

You first have to be registered as a member of my blog. You can register by clicking on “Register" in the menu at the top right of the header. Once you are registered you receive an e-mail to activate your registration. When your membership is activated you can login by clicking on “Login" in the menu at the top right of the header. When you are logged in you can post comments, and to be honest, comments are highly appreciated! Maybe I can use them to help me making the content better and more interesting for you, so feel free to log in and let me hear what you think!

Newsletter
A lot of people asked me "am I not registered, I subscribed to your newsletter". This is something completely different. Subscribers to my newsletter get an e-mail on a regular basis, with the most recent updates from my blog. People who become registered members can post comments. So if you also want to subscribe to my newsletter, you can do this by clicking on "subscribe here" under "About" at the top of the sidebar.

Math
23 March 2006
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Binocular/Telescope
You can use any telescope with good optical quality to observe the Moon. A 70mm or 80mm refractor or a 4-inch reflector will be just fine for starters. When you already own a pair of binoculars, use them! There is no need to rush to the nearest astro-store and buy a telescope right away.

I will not discuss (the quality of) telescopes and binoculars in this article. There are many good other resources on the web and in astronomy magazines that can help you on deciding which telescope or binoculars to buy. You can find some useful links in my beginner's pages and equipment links on my old website, backyard-astro.com. The best advice I can give you before buying any astronomy related equipment: take your time, go to a local astronomy club or visit a star party and look through different instruments yourself, before you decide what to buy. In the end, this will save you a lot of disappointment and money.

Map of the Moon
You need a map of the Moon because you will be visiting a place that (until now) is unknown to you. You need a "roadmap" to find your way around. There are many lunar maps available from bookstores and from Internet stores like Amazon and Sky Publishing, but for outdoor use my favourite is the “Field Map of the Moon” from Sky and Telescope. This map is laminated, so it can be used outdoors under all weather conditions. You will find about 1,000 features labelled (and indexed) on the map. The map is made by Antonin Rukl, who (IMHO) is the best lunar cartographer around right now. You can get this map in two versions, the "normal" naked eye view version, and a mirror-reversed version. Before ordering, check which one you need for using with your particular binocular or telescope. This depends on the type of instrument you are using for observing the Moon. Just have a look at the three images below (click to enlarge).





Compare the views of the Moon through your telescope/binocular with these images. If you see the Moon as shown in the first two images, you will need the standard map (for naked-eye-views, binoculars and reflectors). If you see the Moon as shown in the third image, you will need the mirror-reversed map (for telescopes that work with a star-diagonal, like refractors, maksutovs and cassegrains). If you’re not 100% sure which one you need, just contact Sky and Telescope before ordering.

A lunar map will help you to identify the different lunar features, so it is one of the basic things you need when you start observing the Moon. When comparing your telescopic views of the Moon with a lunar map for the first time, you’ll probably wonder where to find east, west, north and south. The image below should help you finding your way around. I highlighted four key-features that should help you to get the directions right: Mare Imbrium (north), Mare Crisium (east), Tycho (south) and Mare Humorum (west).



Lunar directions


When is a good time to observe the Moon?
The answer to this question is very simple. Whenever the sky is clear and the Moon is visible. The Moon always has some interesting features to observe, even the full Moon. The bright lunar rays for example, are at their best when the Moon is full. A full Moon is also very useful to train your lunar orientation and find your way around as a beginner. Try to identify all the dark area’s, the Maria or seas, when the Moon is full.

What can you observe as a beginner?
When observing the moon through a telescope or binoculars for the first time, you will probably notice two things: there are large bright and dark areas on the lunar surface and the views along the line that separates the dark and light hemispheres of the Moon are the most spectacular.

1. Dark and light areas on the Moon, the Maria and Terrae

Roughly, the lunar landscape can be divided in two types of surface, the dark areas or Maria and the light areas or Terrae. The Maria, or seas, are the grey smooth plains on the lunar surface. The Terrae, better known as highlands or uplands, are the bright and rugged areas of the Moon, full with craters, mountain-ridges and other interesting features. The image below, should give you an idea about the dark seas and bright highlands. It is heavily processed to bring out the contrast between the two types of terrain. Anyway, trying to identify the different dark and light areas is a very good starting point for a beginning lunar observer.



Dark and light areas, Maria and Highlands


2. Highly detailed lunar features along the terminator

You will be amazed by the amount of detail you can observe along the terminator, the line that separates the light from the dark hemispheres of the Moon. When you observe the moon on a few consecutive nights you will notice that the terminator creeps over the lunar surface from east to west, changing the views not only from day to day, but also from hour to hour. You can see craters, mountains, rilles, domes, wrinkled ridges and more. I shot the image below on the 28th of March 2004. It shows part of the terminator of a 7-day-old Moon. As you can see, the amount of detail is simply overwhelming.



The lunar terminator


You can try to identify some of the larger craters for starters. If you need some kind of guideline or list of features to observe, follow this link to the Lunar Club of the Astronomical League. They have an observing list of lunar features, which will keep you busy for a while.

Conclusion
So if you want to observe the Moon, get a map, a pair of binoculars or a small telescope, and start with simply enjoying the views you get from this wonderful object. Try to identify the different mare and highland areas, and if you’re up to it, maybe some craters or other interesting features along the terminator. Maybe you get hooked and want to learn more about the Moon, start imaging the Moon, get into lunar geology, or just simply enjoy the views. No matter what you do, keep in mind that the single most important thing about amateur astronomy (and in fact every hobby) is that you are having fun and enjoy what you are doing.

Happy viewing!


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Why use the Zeiss for lunar imaging anyway?

TAL 200K
My 8-inch TAL 200K is an f/10 (2000mm focal length) telescope, and is only fit for use with 1.25 eyepieces. I achieve the lowest possible magnification using the 32mm Televue plossl. This eyepiece gives me a magnification of 62.5x, and with a 50-degree apparent field of view, this results in a true field of view of 0.8 degrees or 48’. The Moon has an apparent diameter of 30’, so visually the full Moon fits nicely into the field of view, but it fills the view almost completely. There is not much “space” left around the lunar disk.

However, shooting a picture of the full Moon (or nearly full Moon) with this setup is impossible. When the camera is connected to the 32mm eyepiece and the TAL 200K, the view will suffer from severe vignetting (a kind of tunnel-view). I can get rid of this problem by zooming in on the Moon using the camera’s optical zoom, but then I cannot fit the lunar disk completely into the field of view of the camera. At the bottom and the top, a part of the lunar disk is “cut off”. So the TAL 200K is excellent for shooting detailed images of the Moon, better than all other telescopes I own, but for imaging a (nearly) full Moon, I need another telescope.

TAL 100RS
Since two years I have been using the TAL 100RS, a 4-inch f/10 (1000 mm focal lenght) achromatic refractor, to shoot my overall lunar images. With the 32mm eyepiece I get a true field of view of of 1.6 degrees or 90'. Using this telescope got me some satisfying results, but the problem with achromatic refractors is that you get a more or less bright, somewhat colored circle around bright objects like the Sun, the Moon and the Planets. When processing the images I shot with the TAL 100RS, the bright fringe around the Moon becomes even more apparent. I simply need yet another telescope for shooting the overall lunar images. The solution to the problem came from a totally different instrument, a birding scope.

ZEISS DIASCOPE 85MM
During the last few years my girlfriend and I have gradually taken on the hobby of birding, not only during vacations, but also throughout the year, around our home and in our backyard. In 2005 we decided it was time for a birding scope. The choice was rather easy. There are three different top-class birding scopes available, Zeiss, Leica and Swarovski. These have all been tested many times, and you can find enough test reports on the Internet.

We chose the Zeiss because we simply liked the views we got from it, and we liked the professional finish of this wonderful instrument. Because of the high quality and the short focal lenght, this little scope is not only perfect for birding, but also for imaging the full Moon. The Zeiss Diascope 85 is an f/5.5 (focal lenght of 500mm) apochromatic refractor. With the 32mm Plossl eyepiece, the true field of view is almost 3 degrees, or 180'. So there's lot's of space around the Moon, and no colour fringe! However, for shooting detailed lunar images I will allways use the TAL 200K (shows much more detail on the surface because of higher resolution).

The eyepieces
For birding we only use the Zeiss 20-60 Zoom eyepiece. You cannot change eyepieces when you've got a bird in focus, because birds have the strange habit of moving around, especially when you want to shoot an image! Sometimes it seems like they don’t like being photographed.


Luckily the Moon moves a bit slower across the sky (and not in all different directions like those.... birds). Using an adaptor enables me to connect all astronomy eyepieces I currently own to the Zeiss. The 32mm Televue Plossl and the whole range of Vixen Lanthanum eyepieces, they all come into focus, even the 2.5mm Lanthanum, which results in a magnification of 200x. I am convinced that there are a lot of astronomy eyepieces on the market, that will not come into focus with the Zeiss Diascope, but that’s no wonder. The Zeiss Diascope is a birding scope, not an astronomical instrument. So be careful when considering this instrument for backyard-astronomy!

The setup for birding and for imaging the Moon
Shooting images of birds or the Moon has two problems in common: how do I get the object into focus, and how do I shoot the images without touching the camera, resulting in vibrations and .......blurred images. To make life a little easier I chose for a complete adaptor-set from Eagle Eye OpticZooms in the UK:

1. A digimount adaptor for connecting the camera to the eyepiece;
2. A Shutter-release arm and wing 4500 bracket;
3. A 10-inch shutter-release cable;
4. A micro fiber lens cleaning cloth.

On the images below (click on the images to enlarge them) you can see how everything is connected to each other. The shutter release cable works mechanically. You do not have to touch the camera to shoot your images. The X-tend-a-View Pro is just great. It magnifies the 1.5-inch TFT color monitor on the backside of the camera with factor 2. The view is so detailed you can even see the different colors of the individual pixels. It is a great help for focusing the camera/telescope on a bird, the Moon, or whatever other object. With the shutter release arm and the wing 4500 bracket, both the shutter release cable and the X-tend-a View Pro are connected to the coolpix 4500.







Click on images to enlarge


So this is the setup I use for birding. The setup I use for imaging the Moon is basically the same, only the eyepiece and the eyepiece adaptor are different. You find more info on how the Televue Plossl and Vixen Lanthanum’s are connected to my camera on my old website, backyard-astro.com. Just follow this link to get there. The shutter release cable and the X-tend-a-View Pro are used for shooting the lunar images as well.

Anyway, I want to finish this article with a close-up (award-winning) shot of a sparrow, shot with the birding set-up. In a contest from the Dutch Bird Protection (Vogelbescherming Nederland) my girlfriend was one of the ten prize winners with this image. Not bad for a beginner . I hope that in the next months these everlasting clouds will disappear over the city of Landgraaf, and I will be able to shoot a few lunar images with the Zeiss to present them to you in this blog.

Clear Skies to all of you!


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