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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.
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
Image from SkyTools2 by CapellaSoft, click to enlarge!


Posted by Math on 04/30 at 10:06 AM
Deepsky observing • (5) Comments • (0) TrackbacksPermalink

Many times when I am out observing and the sky turns less then perfect I tire of trying to find some of the deep space objects on my list.  This usally happens when I use my 10” DOB.  It is nice to have some alternatives to practice my hunting techniques.  Also seeing colors in stars is a real treat.

This four part (so far) list of doubles and mulitples really is nice because it includes charts that I can use to star hop to my targets.

Thanks an awful lot for sharing these with us and including the charts.  I am gathering these up and will be giving them to some new to observing folks and I am sure they will appreciate them.

James T. Morgan
morganjt56@yahoo.com

Posted by  on  06/07  at  03:30 PM

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.

Posted by sanat  on  06/24  at  04:18 AM

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