Archive for the ‘Open cluster’ Category


Sketching NGC 6633

October 7, 2015

Wedel NGC 6633 2015-10-06 - inverted and cropped

As long-time readers will recall, I have been bully on the idea of sketching DSOs for a long time. I have been inspired by the careful observations and sketches of Doug Rennie and Terry Nakazono in particular. So I made up a blank observing form (which is now up on the sidebar here), printed out some copies, and decided to finally give it a shot. I was going to do M57 first, and kick off my much-discussed, long-delayed Suburban Messier project. But I’d just been emailing with Doug and he’d recommended NGC 6633 as a rewarding open cluster for visual observation, and as I was flipping around in my Pocket Sky Atlas I noticed that it was well-placed high in the southeastern sky.

I was rolling with the XT10. I figured that whatever target I went for, I’d want to capture as many background stars as possible, and the XT10 has much better light grasp and angular resolution than anything else I own.

I started at moderate magnification with the 8-24mm zoom but kept backing out to try to get more context for the cluster, and I ended up with my trusty old 32mm Plossl. The transparency here was appalling. The sky looked clear, in that there was no naked-eye-visible haze or clouds, but it was very humid, and all of that water vapor in the air was bouncing back the city lights like crazy. The sky was about as bright as I have seen it without actual clouds up there. Here’s a measure of how humid it was – all of my exposed stuff dewed up! I don’t think that has ever happened to me here in Claremont.

Wedel NGC 6633 2015-10-06

As far as my method – I was using a 0.5mm mechanical pencil and a click eraser. I started out by trying to frame the field of view with some bright ‘anchor’ stars and then interpolate between them to flesh things out. This proved frustrating – inevitably I’d get one region ‘starred in’ to my satisfaction and then see that its geometry was off compared to a neighboring section. So I did a fair amount of erasing and repositioning. On the first pass I was mainly trying to get the positions of the stars correct.

Then while I was still at the eyepiece I went back and ‘brightened’ up some of the stars by drawing over them with slightly larger circles. I tried to sort them into about five bins, from the bright star south of the cluster, through the brightest anchor stars, the major cluster members, the minor cluster members, to the barely-theres.

Finally, when I brought the drawing inside I touched up a few stars that were noticeably out-of-round.

So the drawing you see here is the ‘rough’ drawing, but with about three layers of revision layered on top. I don’t know if this is good practice or not, it’s just what I did this time, pretty much making everything up as I went along.

As for the cluster, NGC 6633 has a fairly recent nickname: the ‘Italy cluster’. Here’s a diagram from this blog, with my sketch inverted and rotated to match:

NGC 6633 comparo

I can buy it. I wouldn’t have ever picked out that by myself, but I can see the shape in my drawing, and I didn’t know it was there when I was drawing it.

So, I have rather mixed feelings about all of this. While I was doing the sketch, all I could think about was how difficult it was, and how badly I was screwing it up. But I’m fairly happy with the result – it is at least recognizable as NGC 6633 – and I know that I know that cluster and the surrounding starfield a lot better now. Probably better than I know any other single object. I can’t think of another time that I invested so much time and energy on a single observing target.

Maybe this is the beginning of wisdom.

UPDATE October 26, 2015

Here are a couple of sketches of NGC 6633 sent along by Terry Nakazono with permission to post. Thanks, Terry!

NGC 6633 at 31X (7-19-12)

From July 9, 2012.

NGC 6633 at 44X (6-28-13)

From June 28, 2013.


NGC 6645–the cosmic maw

August 19, 2012

I was out hunting Herchels last night and observed the open cluster NGC 6645 for the first time. From my notebook:

Fairly large open cluster. Not sparse, loads of stars, but all are about equally dim–none really jump out. Has an unusual dark spot in the middle like a mouth or the entrance to a cave. That plus five radiating chains of stars make it look like a howling monster.

This didn’t occur to me until today, but I finally realized which monster it put me in mind of–the Beholder from D&D. This sketch gives a sense of its appearance, although it does vary a bit with aperture–that artist saw “a pretty faint unresolved gray haze with about 30 dim stars visible” whereas the 10-inch resolved it completely, with mini-clusters around the central hole and long chains of stars radiating away like nerve endings from a cartoon neuron.

Anyway, this open cluster is well-placed in the early evening, it’s not hard to find, and it has a lot of character. Well worth tracking down. You can even generate a custom finder chart for it using the interactive star chart at, which I just learned about.

What does it look like to you?


Observing report: back in the saddle

October 9, 2011

Last weekend London and I finally went camping again, and I finally got the scope back out under reasonably dark skies. My  last serious outing had been to Joshua Tree at the beginning of May. There are several reasons for the long hiatus.

  • The first is simply heat. We do most of our camping in the spring and the fall because it’s just too darn hot in the summer, at least at our preferred desert destinations. Yeah, we could go up into the mountains and fight everyone else trying to do the same, but I’ve never felt any strong motivation to do so. A big part of going camping, for us, is to get away from crowds of people, which is one of the many reasons we like the desert.
  • The second is teaching. My day job is teaching gross anatomy at Western University of Health Sciences in Pomona. The anatomy courses run from mid-June to the end of October, and during this stretch I usually have little time or mental energy for anything besides anatomy.
  • The third is research. My appointment at WesternU is half teaching, half research. Usually I do almost nothing research-related during teaching time; I have from November through June to worry about dinosaurs. But this year a couple of big research-related events intervened and kept my head in the research arena even during teaching time. The first was a paleontology and anatomy conference in England in September, which I attended and spoke at. The second, and far more intense and important, is that at the beginning of August I took on my first graduate student. Which has been a lot of fun, but has also eaten up the spare cycles that I would normally devote to astronomy.

So, to sum up, the heat has kept me out of the desert, teaching has had its usual effect of monopolizing my attention, and research has scavenged what little teaching left over.

Until last weekend, anyway, when I was overtaken by one of those too-rare bouts of clarity in which I say to myself, “Why on Earth am I overthinking this? Camping is fun and easy, and packing the car takes less than an hour. We should just go.” And so we went.

Despite the earlier bad news, the Salton Sea State Rec Area is still open, at least for now. Don’t know if that’s because the state backed down of full closure, some community group stepped up to keep it open, or no-one’s gotten around to actually stringing a chain across the entrance (I jest; the lights and water were on, and there was a camp host present). That’s pretty much my default destination: it’s close, reasonably dark, has good horizons, is paved all the way in, and has lots of room for London to roam in relative safety with little supervision (i.e., flat, no cliffs to tumble over, and the water is too nasty to contemplate any sort of activity that might lead to drowning).

We got there right at sunset and quickly set up camp. Which basically means setting out the telescope, camp furniture, water, and food, moving all the other gear into the front seats, and making our beds in the back of the Mazda. I like to have all of this squared away before dark; come 3:00 AM I want to be able to climb into an already-made bed and just crash, and not futz around with making any further arrangements. I also got a fire going, and pretty soon we were roasting hot dogs and the making s’mores, our usual camp fare.

The young crescent moon was setting across the water, and as darkness fell the bats came out and started zipping through camp like little silent stealth fighters. London and I dig this; the bats are fun to watch and it’s nice to know that they’re around and keeping us bug-free.

London’s astro-enthusiasm waxes and wanes, much like my own. On some nights all he wants to do is lay out and watch for satellites and shooting stars, and other times he wants to do his own things. Last Saturday he climbed into his nest in the back of the car and played on his Leapster for about an hour (the most time he had spent playing with it in weeks), while I spent some quality time taking in the young crescent moon. I had the wrong camera along. Whereas my decade-old Nikon Coolpix 4500 is endlessly user-adjustable when it comes to settings, my newer Coolpix L19 has no way to manually set the exposure time, so it’s worse than useless when it comes to digiscoping. And the 4500 was back in my office. So no moon shots this time around.

After a while London was ready for some Daddy time so he crawled into my lap and we took turns telling stories until he got sleepy. Sometimes he’ll actually go to sleep in my lap, which is nice, because I know the days for that are growing short. But this time he recognized when he was sufficiently tired, took me to the restroom for his nighttime ablutions, climbed into his nest in the back of the car, and fell asleep almost immediately.

Unlike my outings this spring, this time I wasn’t attempting a Marathon or working on a big observing project. I just wanted to plink around the sky and reacquaint myself with the craft of observing. As usual, I split my time between telescope and binoculars.

This is a great time of year for observing: the summer constellations are still up right after sunset, and by just after midnight the winter constellations are rising. I started with the Great Glob (M13), the Ring Nebula (M57), the Wild Duck Cluster (M11), and Albireo, one of the finest double stars in the sky. By then Jupiter was high enough to be out of the near-horizon roil and showed about half a dozen dark cloud belts in the XT10, and some finer storm detail. After Jupiter I moved on to some autumn favorites: the Pleiades (M45), Andromeda galaxy (M31) and its satellites (M32, M110), and the Double Cluster (NGC 869/884). I could see some hints of the dust lanes in the Andromeda galaxy, but nothing like I saw last fall at Afton Canyon; the Salton Sea is dark but not that dark.

Those were all telescopic observations, and they had  carried me around the sky to the north, where the winter Milky Way was rising. I flopped into the lounge chair, grabbed the 15x70s, and laid back for some binocular stargazing. Cassiopeia in particular is a fantastic area to explore with binoculars; there are so many star clusters that the trick is not usually finding them, but figuring out which among the dozens you’re looking at. I thought about grabbing the atlas and sorting through it all.

Instead, I fell asleep.

I woke up about an hour later, at half past midnight. Normally, I would have called it a night, but during my reverie Orion had strode over the eastern horizon. Now this was too good to pass up. I went back to the scope and spent some time looking at the Great Nebula in Orion (M42/M43), the Crab Nebula (M1), the trio of Messier clusters in Auriga (M36, M37, and M38), and another cluster near Auriga (NGC 2281). I went back to the Pleiades, and got my best-ever view of the Merope Nebula, one of the many faint wisps of nebulosity that surround this bright young cluster. (In retrospect, the clarity with which I saw the Merope Nebula should have sent me scrambling back to the Andromeda galaxy to look again for dust lanes–the sky had evidently improved in the intervening two hours.)

Pleiades by Rob Gendler, borrowed from APOD

Then it was back to the lounge chair and binoculars to revisit all of these targets and more. And eventually, back to sleep under the stars. I did wake up later on and crawl into the car for some deeper sleep, but falling asleep under the splendor of the Milky Way was one of my favorite experiences in astronomy.

I was away too long. I can’t wait to go back out and do it again.


Birthplace of suns

October 16, 2010

Normally I loathe just reblogging stuff from elsewhere on teh t00bz, but I make exceptions. Sometimes it’s nice to have your sense of wonder not just tickled, but smacked right across the room. This picture of NGC 346, from APOD, did it for me. Click through to the astronormous hi-rez version, and spend a few minutes zooming in and out. While doing so, try to hold these two ideas in your head at once: first, this is just one star-forming region in the Small Magellanic Cloud, which is a small satellite galaxy of the Milky Way, which is a big spiral galaxy in a small galaxy cluster on the outskirts of a not-terribly big supercluster, and so on and so forth; and second, every star in the picture is a sun, each with its own history and fate, most with their own systems of planets–and so on and so forth.

If NGC 346 was our entire universe, we could spend a thousand centuries exploring it and not exhaust its wonders. And yet you would not have to venture far into the closer galactic superclusters to find more galaxies than there are stars in the photo, each galaxy with more stars than you could count in a lifetime, each star with its own unique history.

Right! Enough of that! Back to fighting over our speck of dust.


The Moon and Pleiades, again

March 24, 2010

I wasn’t happy with the photo/sketch of the Moon passing the Pleiades that I showed in the last post. The field of view was too cramped to match what I saw at the eyepiece, and I put the stars in by flipping back and forth between Stellarium and GIMP and eyeballing things.

So this time I did it right: got a screenshot from Stellarium, pasted it into a layer in GIMP, placed the stars in a separate layer on top of that, and then got rid of the screenshot layer. Here’s the result, which is very close to what I actually saw Saturday night:

I liked the new version so much that I made a full-screen version. I don’t have any eyepieces that can actually show this much sky at once, but it looks pretty and I don’t care. Here it is:


Observing Report: A New High

March 21, 2010

Last night I was back down at the Salton Sea. I got down there right at sunset, found a spot in the Mecca Beach campground, and got the scope set up a little after 7:00. The sites on either side of me were empty but I had neighbors farther down the way and across the road that runs through the middle of camp. I walked around and invited people to come see the moon.

About eight people drifted in over the next hour or so, and most stayed for quite a while. We looked at the waxing crescent moon, Venus, Mars, the Great Nebula in Orion (M42), the Beehive (M44), M41 in Canis Major, and Mizar and Alcor. Saturn got up out of the near-horizon murk so we got a good look at the ringed planet and four of its moons. Mars showed a polar cap, some dark surface detail, and a possible cloud near the equator. Eventually we went on to galaxies–M81 and M82 in Ursa Major, which looked awesome in the same field of view, M55 and M56 in Leo (ditto), M51 and its satellite, and, most memorably for me, the Sombrero Galaxy (M104). The dark lane of dust that runs across the Sombrero was easy to see, and under those dark skies the galaxy showed a surprisingly extensive halo extending above and below the plane of the disc.

I’ve started working on the AL Caldwell Club so I spent some quality time on a couple of planetary nebulae, the Eskimo or Clown Face Nebula (NGC 2392) and the Ghost of Jupiter (NGC 3242). The Eskimo showed its prominent central star or ‘nose’, and in averted vision I could see some detail in the gaseous halo, but it was small and short on detail compared to the Ghost of Jupiter. The latter nebula was just awesome–it seemed about twice the diameter of the Eskimo, and there were definitely at least two concentric shells of gas around the central star, with the inner shell being brighter than the outer and clearly elongated out of round. Look at this image from about ten feet away and you’ll have a pretty good idea of what it looked like in the eyepiece.

I got a good look at Omega Centauri, the immense globular cluster that just gets over the southern horizon here. It was suffering from being down in the dense atmosphere near the horizon, but it was still a big ole ball of stars. At 92x, it looked as big or bigger in the eyepiece than M13, the Great Glob in Hercules, looked at 184x, and its stars looked smaller and more numerous. It is truly an outstanding object.

And speaking of M13, it was pretty darn good once  it got a good way up the eastern sky, with lots of resolution and long chains of stars emanating from the central ball.

It was  great night. As much fun as I had during the Messier Marathon last month, I had more fun last night just surfing around the sky and showing people cool stuff. I got better views of planetary nebulae, globular clusters, and galaxies than I have ever had from my own scopes. But the most amazing thing I saw all evening was, believe it or not, the moon.

I set up the telescope right before dark, tweaked the mirror alignment, and got the scope on the moon just by dead reckoning, without using the finder. The moon was exceedingly detailed and the entire globe stood out very clearly against the sky, which was not yet fully dark. And the moon was surrounded by stars, which was weird. Admittedly, it was still just a crescent moon, but between the glare from the moon and the evening twilight I didn’t expect to see any stars at all in the same field. They were there,  though. It occurred to me that the moon might be passing in front of a star cluster, as happens from time to time. Finally I got around to checking the finder scope and saw that the moon was cruising right past the Pleiades.

The view in a low-magnification eyepiece was indescribably beautiful, but I’ll try to describe it anyway. With the sky not fully dark, the razor-sharp moon seemed to hang suspended in front of a dark velvet blue sky, with the stars shining out like a halo of fireflies. The impression of depth was overwhelming–I could almost reach through the telescope and pluck the visibly spherical moon from among the streams of stars. Intellectually, I know the distances are all wrong–the velvety blue sky was in front of the moon, not behind it, and the stars were incomprehensibly more distant–but that’s what it felt like.

I took my best photo from last night and mocked up a very crude representation of what this looked like at the eyepiece. Imagine trying to tell someone about Michelangelo’s David when all you have to show them is a doodled stick figure and you’ll have a sense of what I’m up against. Nevertheless, here goes (image processing in GIMP, star positions from Stellarium):

UPDATE: I made a much improved, more realistic version of this image and put it in the next post.

So, I have a new favorite sport: catching the moon in front of star clusters during twilight. I’m sure it won’t happen that often, but the memory of just this first catch will last a lifetime. It was, hands down, the most incredible thing I have seen in any telescope of any size, anywhere, ever.

Best of all, it was accessible–anyone pointing even the most modest telescope skyward at the same time last night would have seen the same thing. So stay alert, you never know when the most seemingly ordinary of celestial objects will jump up and blow your mind.


Mission 19: Cross asterism near NGC 2281

March 4, 2010

Mission Objectives: Asterism, Open cluster

Equipment: Binoculars, Telescope

Required Time: 3 minutes

Related Missions: Diamonds from the Ring of Fire

An asterism is just a pattern of stars that grabs someone’s attention. Asterisms differ from constellations in that they don’t have any official standing, although some like the Big Dipper (which is only part of the constellation Ursa Major) are better known than their host constellations and have been recognized for far longer. Since asterisms don’t have to meet anyone’s standards for asterism-hood, anyone can point one out, and stargazers have been discovering them for as long as humans have watched the skies.

I noticed this one for the first time a few weeks ago when I was hunting down NGC 2281 with my 15×70 binoculars. It’s an easy catch–just find Capella, trace a line to Menkalinan the next star counter-clockwise in the ring of stars that marks the constellation Auriga, and extend the line an equal distance in the same direction. Might as well take in NGC 2281 while you’re there–it’s just southwest of the right arm of the cross.

NGC 2281 is a nice little open cluster for either telescopes or binoculars–another glittering diamond in the celestial Ring of Fire. But in this case, I like the asterism better than the cluster! It’s well worth seeking out, and definitely better in binoculars than in telescopes.

The cross asterism seems really obvious, but I haven’t found any other mentions of it so far. Does anyone know if it has been noted or discussed before? I’ll be grateful for any info.