THE BIG DIPPER stands high in the northeast on spring evenings, giving no sign of the countless faint wonders that lie hidden in and around it. To small telescope users, the Dipper is best known for the bright double star Mizar in the middle of its handle. But this part of the sky also contains scores of galaxies within reach of a modest telescope. Rarely do they get the attention they deserve.
Far behind the stars of the Dipper, some half million times farther away, lies ,an outlying tendril of the gigantic Virgo supercluster of galaxies. The secret to searching out these dim, distant riches is having good charts - and skill in using them to pinpoint a difficult object's exact location in the eyepiece.
Why not have a try tonight? We'll take a step-by-step tour through one small galaxy-strewn area just off the end of the Big Dipper's handle, in the constellation Canes Venatici.


1. Eta (77) Ursae Majoris.
Our starting point is the star at the end of the Big Dipper's handle, also named Alkaid (see image above). It is 2nd magnitude, a bluish white main sequence star of spectral type B3. With a color index of - 0.2 it is nearly as blue as stars get, though the hue is quite pale. The blue tint becomes more evident when the star is out of focus. Alkaid is estimated to be 300 times as luminous as the Sun and 140 light-years distant. Sight on it to make sure your finderscope is correctly aligned with the main telescope.

2. M51, the Whirlpool galaxy. This is one of the amateur showpieces of the sky. At any star party you can bet that the large telescopes pointing toward the Big Dipper are showing off what they can do on M51. The ability to find it without charts is considered a star-party badge of virtue.
For all that, M51 is not as grand a sight as its reputation (and photographs) imply. It is only one fifteenth the diameter of the great Andromeda galaxy, M31, and only a hundredth as bright, To find M51, start from Alkaid and move your telescope 2° westward - be sure that you have the direction right! - to pick up the 5th-magnitude star 24 Canum Venaticorum.

Now go southwest and find the three stars that form a equilateral triangle. M51 is located just below the bottom line and closer to the left star as seen in the image above. You're now on top of M51 and its companion galaxy, NGC 5195. Another 7th-magnitude star lies just 1/3 ° to their east. In a 6-inch reflector at 45 power under moderately light-polluted skies, M51 and its companion are a pair of hazy gray glows with brighter centers. They are just 4' apart. Of the two, M51 looks much larger and rounder and its center is brighter.



M51
Keep looking, for in time you'll gradually perceive more detail. Try high powers on these galaxies, and patiently search their depths with averted vision for any dim secrets they harbor. At 200x the companion shows a bright, almost stellar nucleus that is definitely more concentrated than that of the main galaxy. Moreover, the companion seems to suffer a sharp cutoff in brightness just east of its nucleus, as if peering out from behind a dark dust cloud - an impression that photographs confirm. An 8-inch telescope under a good sky begins to show traces of spiral or ring structure in M51. Indeed, this is the galaxy in which spiral structure was first discovered. A 17-inch scope makes the spiral shape obvious. A third galaxy, much smaller and fainter and usually overlooked by amateurs, lies south of M51. NGC 5198 forms the fourth corner of a little rectangle.
It can be seen at all in the 6-inch at 110x. Despite its location, NGC 5198 is not a second companion of M51; its redshift shows it to be about four times as distant. If M51 and NGC 5195 are about 30 million light-years away, NGC 5198 is about 120 million.

3. M63. Is just east-southeast of an 8.5. magnitude star. M63 looks brighter than M51 in a 6-inch. It is very elongated nearly in the direction of the star. Time and averted vision bring out a much larger, outer disk. The spiral galaxy M63, about 35 million light-years distant, is probably a near-copy of the Milky Way. The appearance of its faint outer arms on high-quality photographs has earned it the name "Sunflower galaxy."
M63
4. NGC 5005 and 5033. Work your way south from M63 through three little asterisms. The first includes 19, 20, and 23 Canum Venaticorum; the second 15, 16, and 17. The third, about 11/2° farther south, is a faint, nameless little east-west stream. Here lie the two galaxies NGC 5005and 5033.
The former is easy in a 6-inch telescope - very elongated northeast to southwest, with a central bulge and signs of a bright nucleus. This is the way a galaxy ought to look! There are hints of a sharper edge along its southeast.
NGC 5033 is quite a bit fainter but still not hard in a 6-inch. It looks more amorphous, with no sign of spiral arms.
Try high power on these galaxies to see if it reveals any more detail. High powers can be a boon even on very faint extended objects.
5. Cor Caroli. After searching out all these dim sights, the double star Cor Caroli (Alpha Canum Venaticorum) is a blaze of glory. It's two components, magnitudes 2.9 and 5.5, are 19" apart - wide enough to separate in any telescope. At 45x in a 6-inch, the bright component looks white with possibly a touch of blue; the secondary is an odd tawny yellow. At 110x the secondary appears to have a sort
of purple-brown tint, and at 280x, when the stars are magnified to fuzzy balls, the purple is undeniable. As with many doubles the colors are largely contrast illusions in the eye. The stars' spectral types are AO and F10.
6. M94. Exactly 3° north-northwest of Cor Caroli is this fine 8th-magnitude galaxy. It's so bright you can probably hit it just by noting its exact location on a chart with respect to Alpha and Beta Canum Venaticorum. M94 is rather small as well as bright, so it takes high power very well. It looks almost round. Its light increases steadily toward a brighter nucleus "much like an unresolved globular cluster. M94 in a 12-inch telescope, reveals patchy irregularities in the galaxy's outer parts.
M94
7. NGC4490 and 4485. These colliding galaxies are easy to locate just 2/3° northwest of 3rd-magnitude Beta. NGC4490, with a total visual magnitude of 10, is the first you'll see. It's fairly easy in a 6-inch, a gray glow elongated northeast southwest. Use averted vision to search for the much more difficult NGC4485 located to its north-northwest. A larger telescope under a darker sky may show that the two are attached.
8. NGC4449. Moving north brings us to our next way station among the island universes. NGC4449 is a large irregular galaxy with a catalogued size of 5 by 4 arc minutes and a total visual magnitude of 91/2. In a 6-inch it is a dim but easy patch of glow. This galaxy is a little nearer than the others we've been looking at, assuming its redshift can be trusted as an accurate distance indicator. If NGC4490 and 4485 are 30 million
light-years distant, NGC4449 is only about 10.
North of NGC4449 by 0.7° is the pretty double star Struve 1645. Its two white components, magnitudes 7.4 and 8.0, are 10" apart.
A mere 8' east-northeast of this pair is very faint NGC 4460, which you're welcome to try looking for. It was totally invisible in the 6-inch.
9. Y Canum Venaticorum. Sweep 3° east from Struve 1645 with your finderscope and ... what's that? You've hit Y Canum, "La Superbal" one of the most colorful stars in the sky. It is a deep, rich orange, a carbon star of spectral type N8. It appears so red not just because its temperature is low but because molecular carbon vapor in its atmosphere is actually red in color. We see the star's surface through a red filter. The star's B - V color index is tabulated as 2.5, but color index values this high begin to lose meaning for visual observers. Robert Burnham calls the tint "truly odd and vivid" in large telescopes. In a 6-inch it is a fiery coal. The color is even redder in a finder or binoculars.
Y Canum Venaticorum is one of the very largest stars known, with an estimated diameter of 10 astronomical units - about one billion miles. It is a semiregular variable, ranging from about visual magnitude 4.8 to 6.3 and back in roughly 5 months. Its color probably varies too.
10. M106. We could wander on forever among the galaxies in this region of the sky. But for now we'll make just one more stop, working 5° northwest to reach the brightest galaxy we've looked at yet.
M106 is big and bold in a 6-inch, very elongated north-south, with hints of irregularities around its ends.

M106
A 6th magnitude star 1/2 ° to the east-southeast makes it fairly simple to locate. Hunting down M106's companion galaxies would be a good project for an 8-inch or larger telescope under dark skies.
M106 is a grand galaxy to contemplate as you try to imagine the impossible - that these misty little smudges are incredible swarms of hundreds of billions of suns, spanning tens of thousands of light-years from end to end. Each probably contains billions of planets harboring a near-infinity of wonders that would shatter the imagination. But we must be content to view them from afar, privileged just to detect them as the merest wisps before packing up the telescope and retreating inside to ponder them in our dreams.