Many of the deep-sky objects we point our telescopes toward have pleasant surprises, some in plain sight, others hidden and more challenging. Let me introduce you to a few.
As kids, we'd take our allowance and buy these boxes of Cracker Jack filled with caramel-coated popcorn and peanuts. I never much cared for the molasses-flavored popcorn, but the peanuts were tasty. Both took a backseat to the paper-wrapped prize at the bottom of the box.
Sometimes I'd fish out the prize before even bothering with the goodies, tearing it open to get something cool like a plastic T-rex, whistle, or even a magnifying glass.
Deep-sky objects are like that. You might seek out a galaxy and discover an unexpected double star in the same field of view. A star cluster may include a striking asterism or an appealing red star. But you've got to rifle through the popcorn and peanuts first to find the prize.
I've selected eight of my favorites, all well-placed in the evening sky this month. Most will be familiar to you and easy to see in any telescope, but I've included a few obscure and challenging objects, too. So many deep-sky objects hold additional rewards that come with repeated observation that narrowing it down to eight will only give you a taste of the treats. That's why I hope you'll share a few of your own deep-sky prizes and surprises at the comments link below. Without further ado:
M103 — Red star and a duplicitous double
M103 is a favorite: a real sparkler of star cluster and easy to find about 1° east of Delta (δ) Cas in the "W" of Cassiopeia. At magnitude +7.4 and 6′ across, you can even spot it in binoculars. Through a small scope you'll notice that most of the cluster's ~40 members are neatly contained within a bright little triangle of stars.
Inside that figure, a lovely 10th-magnitude red giant will catch your attention, while the pretty double star Struve 131 (magnitudes +7.3, +9.9; separation 14″), at the group's northern apex, looks for all the world a bona fide cluster member. It's not. Like Aldebaran in the Hyades, it's a foreground star. M103 lies about a distant 8,000 light-years from Earth, and the double about 2,800 light-years.
Triangulum Galaxy totes a gargantuan nebula
The Triangulum Galaxy holds many treasures for amateur astronomers — flocculent arms, stellar associations, a globular cluster, and multiple bright emission nebulae. Brightest and easiest of the emission nebulae is NGC 604, pinned to a spiral arm about 5′ northeast of the galaxy's center. Shining at magnitude +12 and a tad larger than 1′ across, this knot of nebulosity looks like a small comet until you realize you're seeing a stellar nursery 40 times larger than the Orion Nebula some 2.7 million light-years away! Use high power to see structure (smaller knots) and watch the blob pop in brightness through a nebular filter.
Double Cluster meets the Smiling Cyclops
Every time I look at the Perseus Double Cluster, besides those breathtaking ganglia of stars, I always see a one-eyed, starry smile beaming from the center of NGC 869. The tiny asterism, nicknamed the "Smiling Cyclops" by amateur Will Young, will surely catch your eye if it hasn't already. The solitary "eye" is a bright, slightly variable magnitude +6.5 star. Just to its east lie five or so 9th-magnitude stars in a smiley arc. If you're not into smiles, the asterism also looks like a carat-busting diamond ring. Either way, it's a wonderful prize worth tearing off the wrapper as soon as the next clear night.
NGC 1023 hides a secret
High in Perseus, 5° due west of the Rho (ρ) Persei / Algol stellar duo, the barred lenticular galaxy NGC 1023 makes for a pleasant diversion from winter's plethora of star clusters and nebulae. The 8′ × 3′ east-west elongated streak has a bright central bar and near-stellar nucleus; at magnitude +10, the galaxy requires only a 6-inch telescope. But something else lurks here for those who love a challenge — a 13.6-magnitude companion galaxy with the name of NGC 1023A (a.k.a. PGC 10139). It's barely visible superimposed on NGC 1023's eastern extension.
If you have a 12-inch or larger scope, select a magnification from 150×–250× and use averted vision to look for a misshapen bulge at NGC 1023's east end, a sign of its barred, irregular galactic companion.
Multiplying multiple stars
Fourth-magnitude Sigma (σ) Orionis, located 50′ southwest of Alnitak, the easternmost star in Orion's Belt, is one of the finest multiple stars for small telescopes. Even a 6-inch will show the bright primary accompanied by a short, scraggly line of three companions. The faintest is C at magnitude +10. Sigma itself, also known as Sigma AB, has an extremely close magnitude +5.1 companion (B) only 0.25″ west-southwest of the primary. A 12-inch in excellent seeing at a magnification of 350× or higher might be able to cleave this one or at least show Sigma AB as elongated. I've yet to see it.
When viewing double and multiple stars, I suggest using the lowest magnification necessary to split all components. Too high a magnification can rob these gems of the crispness that make them so aesthetically pleasing.
Ready for your prize? Just 3.5′ northwest of the stellar conga line, you'll be drawn to another multiple star, Struve 761. This trio of 8th-magnitude stars form a skinny triangle that together with Sigma pack the field of view with gobs of bling. A beautiful sight!
If that's not enough, the Sigma quadruple forms the core of a star cluster discovered only in 1996 called, appropriately, the σ Orionis Cluster. That year, a large number of low-mass, pre-main sequence stars were discovered centered on the bright star. You can further your explorations of the cluster with the help of the photograph above.
Moths drawn to a celestial candle
"Where have you been all my life?" That was my reaction on first seeing the sparkly star cluster NGC 2362 in Canis Major. Some 40 stars gather into 6′ of sky under the bright umbrella of Tau. Few clusters are so dominated by one overpowering star, in this case a rare, blazing hot, blue O supergiant. Take a closer look for its two companion stars, magnitudes +10.5 and +11.2, 8.5″ and 15″ away, respectively, in P.A. ~90° (east).
Like some planetary nebulae that flash in and out of view when switching between direct and averted vision, the contrast in brightness between Tau and the other cluster members plays a trick on our eyes. Star directly at Tau, and you'll see only a smattering of stars around it, but glance off to the side and the group blooms like a field of stellar flowers!
Care for a doughnut with that cluster?
The classic case of a surprise buried inside a familiar deep-sky object has to be the little doughnut-ring planetary nebula NGC 2438 superimposed on the bright, rich star cluster M46 in Puppis. The cluster tantalizes even in a 50-mm finderscope, looking like an atomized mist of minute pinpoints. In a 6-inch telescope, M46 spans ½° and if you care to count, there are some 150 stars salting the field.
The arcminute-wide, magnitude +11 planetary nebula looks like a small, gray puff some 10′ north of the cluster's center. Even a 6-inch scope will grab it. Averted vision reveals a dark center and a faux central star that's actually a member of the background cluster. For your best view of this smoky ring, use a UHC or O III filter. You'll be amazed at how much crisper this doughnut will appear. And who doesn't like a crispy doughnut?
Star vs. galaxy
Regulus is Leo's brightest star and a pleasing small scope double. The huge brightness range between the 1st-magnitude primary and 8th-magnitude secondary (located 177″ northwest of Regulus in PA 307°) make this pair jump out even in a 3-inch. But all that brilliance gets in the way when it comes to digging out Local Group galaxy Leo I, located 20′ nearly due north of the star.
I don't know the minimum scope size required to tear open this prize, but I suspect you'll need at least a 10-inch. Although I glimpsed the galaxy in my 15-inch at 70× with Regulus in the same field of view, the best strategy was to use a higher magnification (around 150×) to narrow the field and keep the star out of view. Then, I could clearly make out a faint, oval haze using averted vision.
I hope you'll track down a few of these gems in the coming moonless nights and find all the prizes that await your eye.