Archive for October, 2015


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.


Irregular Mission: You call this stargazing?

October 2, 2015

Why aren’t we looking at stars, again?

When I was a kid, I wanted a telescope. I was enchanted by the romantic idea of sitting out under the night sky (which I didn’t really know, but loved) with a telescope (which I loved, but didn’t know). But I couldn’t afford a telescope, and I hadn’t learned how much stargazing you can do with binoculars (tons, in fact). And actually, had a telescope come into my possession, I wouldn’t have known what to do with it. I figured astronomers just, er, pointed their telescopes at stars.

I mean, stars are the basic units of matter accumulation in the universe, and they’re primarily what you see what you look up into the night sky. If you’re in a sufficiently dark place, you may also see the Milky Way, and a couple of dozen of the brighter clusters and nebulae, and there are a handful of double stars you can split with the naked eye. And the moon and planets may be out, too. But mostly what you can see with the naked eye are an awful lot of individual stars. So ever since I got into amateur astronomy eight years ago, it has greatly amused me that amateur astronomers spend almost all of their time looking at everything but individual stars.

Now, most of those not-individual-star thingies are still related to individual stars in some way. Here’s a tongue-in-cheek breakdown:

  • Double and multiple stars: teeny groups of stars
  • Open clusters: small groups of stars
  • Globular clusters: big groups of stars
  • Galaxies: huge groups of stars
  • Galaxy clusters: groups of huge groups of stars
  • Stellar nurseries: baby stars
  • Planetary nebulae: dying stars
  • Supernova remnants: corpses of stars
  • Bright nebulae: disorganized star dust, lit up by stars
  • Dark nebulae: disorganized star dust, not lit up by stars
  • Planets, moons, asteroids, and comets: organized star dust, lit up by one star
  • The sun: okay, you got me there

Your mission, should you choose to accept it, is to pick one star in the sky, learn a little something about it – how big it is, how bright, how old, how far away – and then go have a look. Doesn’t have to be with binoculars or a telescope, but it can be. Just take a couple of minutes and get acquainted with this actual physical object, a gravitationally-contained fusion bomb blazing away out there in space, shooting intense and continuous beams of photons in all directions for millions or billions of years. As physically real as your own body (which is itself compiled from the fusion-forged dust of long-dead stars), and from the standpoint of the physical universe, a lot more durable, lasting, and important.

Contemplate the unique appearance and attributes of your chosen celestial snowflake.

And then – and only then – look around and see that you are standing in a blizzard – a universe dense beyond counting with stars.