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Small Wonders: Perseus
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Small Wonders: Perseus
Tom Trusock - 11/07
Double Cluster and Heart Nebula - Contributed by Boris Stromar
Welcome to the warrior.
Screen capture from Stellarium
Perseus slew the gorgon Medusa and then (while riding Pegasus) rescued Andromeda - the daughter of Cepheus and Cassiopeia - from Cetus. It's his story that we see overhead on these early winter evenings.
That abbreviated bit of legend out of the way, lets take a look at some of the targets for visual observers in Perseus.
Perseus has a little bit of everything. As it sits astride the winter milky way, you'd expect it to be rich in both open clusters and reflection nebula, but it also has more than it's fair share of galaxies. According to the (admittedly non-exhaustive) databases that shipped with Sky Tools 2, there are 8445 galaxies, 10 Abell galaxy groups, 19 quasars, 23 planetary nebula, 7 diffuse nebula, 42 dark nebula, and 35 open clusters. Truly, this is an amateur astronomers playground!
First lets discuss a couple of naked eye or binocular objects - one that's on the list, one that's not on the list, but is rather interesting to think about, and one bonus (nonlist) binocular challenge object.
Mel 20, the California Nebula and Algol
Mel 20 - Rony De Laet @ 9x
Often called the sword handle (but by the pictures I've seen it's no where near his sword) in the center of Perseus, we find the Alpha Per moving cluster. Also known as Mel 20, this cluster is huge - just over three degrees across and I find the best views are either naked eye or at very low powers. Astride the winter Milky Way, I find Mel 20 to be an inspiring sight - either naked eye or with the smallest optical aid.
The California Nebula and M45 - Boris Stromar
The next target is a challenge object, and one that sticks in my memory as I made an "independent" discovery while imaging Hale-Bopp over 10 years ago. It's an easy photograpic target, but a difficult visual one. I'm speaking of NGC 1499 - the California Nebula. So named for it's shape, photographs of the object are somewhat deceiving for the visual observer. This is a huge target (just under three degrees by 2/3 of a degree) and although it's listed at 5th magnitude, it's extremely low surface brightness makes it very difficult to spot. Your best bet for this one is either naked eye from a very dark site, a small wide field scope or binoculars. In widefield scopes, it's simply a gentle brightening of the stellar background. Some observers have reported positive results when using an H-beta filter.
No discussion of Perseus would be complete without a mention of Algol - the demon star. Algol lies a mere 93ly away and is an eclipsing binary. Every 68 hours and 45 minutes, Algols larger but dimmer secondary eclipses the smaller and brighter primary by 79%. During the 10 hour period this is ongoing, Algol dims from mag 2.12 to 3.39. Algol is really a triple star system, but only the interaction of these two affect the apparent "variability". Interestingly enough, there appears to be matter streaming between these stars. One of the stars has filled a droplet shaped region between itself and it's companion (called the Roche lobe) and is transferring matter over it's Lagrange point. Unfortunately, we can only imagine what this spectacular event must look like. (See the link at the end of the article for more information.)
The famous Double Cluster makes a spectacular target for observers with the slightest visual aid.
NGC 869 / 884
Easily visible to the naked eye from a semi-rural location it seems these two independent clusters have been known since ancient times, being recorded by both Hipparchus and Ptolemy. These two are a spectacular sight, and one that beginning star gazers often stumble upon by themselves while playing "What's that patch of mist?" I'd done this myself when a youth, and it was nearly a year before I located something that could tell me what I'd found. The double cluster holds some special memories for me, and I suspect many of you can say the same. This was one of the first telescopic objects that made my jaw drop, and the visceral memory of seeing this object for the first time is right up there with my first views of Saturn.
Double Cluster - Eric Jacob
Classically, the clusters have often been called h and X Persei, however Archinal and Hynes note that O'Meara and Green have shown that these identifications came about because Bayer showed two objects labeled thus in his Uranometria. Archinal notes that it now appears that Bayer meant X was meant to represent the light of the combined clusters.
Visually, I find this target at best advantage in a wide field telescope. Although I've looked at it countless times over the years, my favorite views have to been through the NP101 with a 13mm Nagler eyepiece (or more recently with the 13 Ethos). This combination yields 42x and nearly a 2 degree (2.5 with the Ethos) field of view. With this combination, the stars present themselves as minute jewels scattered across the night sky. While you're staring, take a moment and look for the dark red gem in the heart of 884. This is semi-regular variable RS Persei whose period id 224 days. RS varies from mag 7.8 to 10.0.
Rodger Raubach contributes the following:
"Rather than a single observation, this is a series of recollections of this magnificent gem. I have viewed the Double Cluster --NGC 869 and NGC 884--through many telescopes. The most memorable view came a frosty evening in December of 2003 with my then-new Takahashi TOA 130. The double cluster was best seen at 29x in a Panoptic 35 eyepiece, which revealed the two small balls of stars, seemingly floating in a rich background of the Winter Milky Way. I had previously seen the Double Cluster in a Celestron C 9.25 and C 14, but neither of those views would compare with the sheer beauty of the wide field view offered by the small refractor."
Moving SW 8 degrees from the double cluster, we come to the first of our Messier objects in Perseus.
This little planetary nebula shows some structure even in small telescopes, and has not one, but two NGC numbers (650 and 651). Most scopes show two lobes of the planetary, with dark area seperating them. In a small telescope, it's a small, but interesting object. At low powers, you'll need to use care when sweeping as it can be passed over rather easily.
It a large telescope, it's jaw dropping. The first time I observed M76 with a large scope was through a buddies 20". Normally I don't make it a habit to look at Messiers with large aperture, and they didn't tell me what the target was, preferring to see if I'd recognize it myself. I was floored to find out this was little bitty peanut shaped M76 that I was so used to seeing.
Each bump in aperture increases the detail seen in this object. In small apertures, it's a peanut that is somewhat comparable to M1. Moving to larger telescopes, and it becomes a rectangular bar of light. In still larger telescopes, I've seen (with direct vision yet) the ansae / wings that are so common photographically, as well as a wealth of detail in the nebula itself. Ironically, even though it's a planetary nebula, I find that I don't care for it's response to an OIII filter and I usually see more detail au naturel.
M76 - Bill Warden
O'Meara notes (The Messier Objects) that M76 is about 5 times more distant than M27, but about the same actual size.
I'm not exactly positive why, but M76 seems to have gotten a reputation as being the most difficult Messier on the list. There are a few things that conspire to work against it: it's small size, it's somewhat (but not really) isolated position, and the fact that it is somewhat dim when compared to a lot of it's brethren. But really, it's not all that difficult of a target.
Move back to Perseus proper and head down the body. Just a little south west of Mel 20, we stumble across NGC 1245. In my 4" apo at 45x, this is a really pretty little cluster. Visible as a patch of mist inside three brighter stars, it pops into definition when averted vision is used. Bumping up the power helps to bring more and more members out, and increased aperture also helps. I like to use as low a power on open clusters as possible - the better to provide an aesthetic framing of the subject.
Bill Warden wasn't able to make the observation in his 80mm f5 from light polluted skies, but he send along the following CCD image.
NGC 1245 - Bill Warden
Now move east of Mel 20, over toward lambda Per. Over here, we find three open clusters of interest, and an emission nebula.
Although it's listed in the catalogs as a bright nebula I wasn't quite able to pull it out in the 4" - however it was handily seen in the 18 as a fairly bright, semi-triangular glow. You might try either an OIII or UHC filter on this one and see what you get.
In the 4 inch, this was a faint, fairly unremarkable cluster that at the best moments resolved into a dozen or so stars at the limits of averted vision. Larger scopes show it to a bit more advantage, and a max of 25-35 stars.
The 4 inch shows a scattering of haze surrounded by a brighter triangle of stars. Look for the coloration of these defining (most likely) foreground stars. Overall I ranked this as a pretty interesting sight for a small telescope, with the geometric patterns drawing my eye back over and over again. I found my best views were with the Ethos at 42x. In a wide field scope, try and see if you can get 1545 and it's larger, yet slightly dimmer companion 1528 (which lies about a degree to the northwest) in the same field.
NGC 1545 - Juha Ojanpera, 11" @ 69x
Although listed as a bit dimmer than 1545, aesthetically I found this one a bit nicer in my 4" apo, showing far more resolution under detailed inspection. Using averted vision, one gets glimpses of dozens of stars, and the attractive field invites you in for a detailed look. Look for arcing star chains extending various directions from the central location of the cluster.
NGC 1528 - Juha Ojanpera, 11" @ 69x
Reader Zizzapnia contributes the following:
(binos, 4.5-inch) Visible as a faint smudge in binoculars. Large and sparse. Half a degree in diameter.
Dominated by a triangle of 7th mag stars: N one is a double. Also an unequal mag double on the N edge
(10-inch) Nice cluster for 62x, fitting nicely. Roughly triangular shape with dark lanes running through it. A smattering of 10.5 and dimmer stars. Some nice rich clumps of stars-a collection of clumps- 4-6 stars in about 6 clusters comprising the main cluster.
Let's move into our last region of the sky for the evening. Here we've got a number of targets; both clusters and galaxies, as well as our challenge objects.
M34 - Eric Jacob
Visible to the naked eye from a dark site, M34 is a fantastic cluster for small telescopes and binoculars. I've never been fond of looking at large clusters with too much magnification - too much simply spreads the view out making it lose some of the impact. M34 is a dramatic illustration.
Rodger Raubach contributes the following:
from my observing notes 1/23/2004. "An easy binocular target; readily picked up in a scan from Almach to Algol. Stars easily resolved at 8x in my IOR Bucharesti 8x40 binos. In the TOA 130 at 29x, it resolves into a lovely collection of bright blue-white stars. I also noted a prominent double, Struve 44, almost in the center of the cluster. Even at only 29x, the telescope nearly overwhelms this object. Probably best seen in a pair of large tripod mounted binoculars." As an additional note, I have picked this up "naked eye" several times on extremely clear dark nights.
M34 - Carol Lakomiak
Dropping 3 and 2/3 degrees almost directly south of M34, we run into the brightest galaxy in Perseus, NGC 1023. This bright galaxy is classed SBO, which means it's a spiral with a central bulge, but no arms. Recent analysis done using the HST and various ground based telescopes has shown evidinence of a super massive black hole at the core - one that's currently whipping some of the (yet captive) stars in it's disk at an estimated 1.3 million miles (2 million kilometers) an hour.
NGC 1023 - WadeVC
My notes indicate it's an easy catch in my 4" apo with the 12mm Nagler (45x). With this aperture, there's simply a wash of light with perhaps some brightening towards the center, but it shows little to no detail. In the 18", a graduation of starlight becomes visible. The light gets brighter towards the middle, while prolonged inspection shows a prominent core and nearly stellar nucleus.
Reader Zizzapna contributes the following:
(4.5-inch) Nice, quite bright, star like nucleus. A number of 8th to 9th magnitude stars close to it. Looks almost edge-on, oriented E-W. Extends out about 5 arcminutes. I lose some visibility of the arms in 180x. E arm a little brighter than the W arm, and extends out a little further.
Two degrees away to the SSE, we find a more difficult member of the galactic zoo:
It's certainly possible to pick this one out in a medium size telescope, but it's nowhere near as exciting as 1023 - that is, unless you were looking at it this summer when Supernova 2007GR was discovered. (See the links for the discovery photograph.) And there was another one in 1961. This is definitely a galaxy to include in your supernova search program. On the typical (non-supernova night) this is just a semi-faint, diffuse 2" glow that shows no sign of a central brightening.
Now move east 9.5 degrees from 1058 and we'll come across the little open cluster NGC 1342. A 4 inch scope shows a rough dozen or two stars. Luginbuhl and Skiff's Observing Handbook and Catalogue of Deep Sky Objects mentions that this cluster resembles a stingray swimming to the west. Granted, I've played a lot of stellar connect the dots, but I just don't see this one. Do you?
I've got three for you tonight.
IC 351 and IC 2003
First up are two planetaries that you can actually fit into the same TFOV of a wide field telescope. IC 351 and IC 2003. The catch? While bright, both are very tiny and stellar at low to medium powers. To identify these, it's going to take a bit of research. Identify the field and pump the power up. Use the DSS photos above to help you identify the field. An OIII filter might also ease the task. Try holding it between your eye and the eyepiece, and flipping it in and out rapidly. The "star" that doesn't dim is the planetary.
In the 18" both are semi-featureless disks (with IC 351 being slightly smaller). There is no sign of their central stars even at 800x.
The next isn't a traditional challenge object - it's a galaxy cluster. Odds are you'll certainly be able to bag some of the brighter components, but the challenge here is to see just how many you can get. It's centered (roughly) on NGC 1272 and the cluster contains some 500 members over some 4 degrees of width. The larger the scope, the more you'll see. Granted, some panning is required, and if you really want to pick out members, you'll also need to spend some significant time at high powers to increase the apparent contrast. In my 18", the 13mm Ethos gives a true field of 1/2 degree and a power of ~180 - perfect for medium power galaxy busting. Centered (roughly) on NGC 1267, I initially picked out a dozen or so obvious candidates in this field alone, while concentrated study bumped that number up even farther.
The one thing that is essential for this one is a good map. Have it printed out, and take it to the telescope for identification. 1272, 1275, 1278 and 1273 make an excellent place to start your explorations. Be sure to take some time and wander to the west south west, down the chain of galaxies that presents itself. Galactic heaven!
And with that, that's it for this month. Once again, thanks to the readers who submitted observations, sketches and photos, there were far more excellent submissions this month than I could use. Your contributions greatly enrich these articles.
As always, I'm gratified if folks find my meanderings useful.
Till next time -
Additional Resources / References / Just Plain Cool Stuff
More on Algol - The Journey Begins, Mercedes Richards
Evidence of a Supermassive Black Hole in the Galaxy NGC 1023 from the Nuclear Stellar Dynamics
StarDate Black Hole Encyclopedia: NGC 1023
SN2007gr Discovery photograph
Best of AOP
If you liked this article, you may want to check out the rest of the series.
I'd love to hear of your experiences under the night sky - please feel free to
e-mail me or send any observing reports to: firstname.lastname@example.org
Please indicate if I can cite your observations in future columns.
Photographic Images Courtesy DSS: copyright notice
Hubble Images Courtesy STSCI: copyright notice
Star Charts Courtesy Chris Marriott, SkyMap Pro 10 Used with Permission
Locational Images Courtesy Bill Tschumy, Where is M13? Used with Permission
Constellation Art from the Freeware Program Stellarium
Special Thanks to Olivier Biot for assistance with the PDF's and all those who
take the time to read and contribute to this series.