Lake Sonoma 11/13/07

Bill Cone

We had very good conditions for the most part: clear skies, mild temperatures, with a slight breeze from time to time. You could feel the humidity in the air, and the dew did come to rest on many surfaces, yet it never fogged my finders. I had my secondary dew heater running as a precaution, but I don't think if it was necessary.

I arrived right after sunset to find Greg and Steve setting up their scopes, as a very warm, saturated, edge to the Earth's deep blue shadow was rising in the East. One could also see warm and cool streaks running across the sky from the West, indicating cloud shadows being cast a great distance through the illuminated upper atmosphere, though there were no clouds to be seen on any horizon. That also indicated a fair degree of moisture in the air, but it didn't seem to impede our observing. As the sky deepened in hue, I took a peek at the moon, and noticed 2 faint stars very close to the shadowed side of the Moon. They were both about to be occulted, so I pointed it out to Steve, who sat down at my scope to take a look. Something distracted him, and when he finally did peek, they were already swallowed up! Not everything up there happens slowly over millenia...

One lone observer drove into the lot as it was getting dark, and I'm afraid we weren't the friendliest, as his headlights had raked over us and our scopes. He introduced himself as Ken, and set up his scope across from us. After that we heard nary a peep from him, and he silently packed up and took off about 90 minutes later.

Since my first view of the comet 17P Holmes a few weeks ago, it has travelled quite a ways towards Gamma Persei, about 5°. As it has skirted the NE edge of Melotte 20, as well as the Milky Way itself, the field is very rich in stars. I counted 22 stars inside the bright coma, including one that was extremely close to the stellar nucleus. The bright coma filled about 2/3 of a field of a 24 Panoptic which put the diameter at around 27', still under the size of the full moon, but awfully large nonetheless. The shape continues to evolve, as our viewing angle from Earth shifts. Though one could still perceive a general roundness, the coma is becoming more asymmetrical in character. the Northern hemisphere of the comet shows a distinct, bright edge, with the brightest portion being the NW quadrant. Behind the bright edge on the Northern limb, there is a darkening of tone in the coma before the eye reaches the brighter inner region that wraps around a stellar point, then elongates towards the Southern edge of the coma. The Southern hemisphere of this object is soft, diffuse, and uneven, seemingly eaten away, or dissolving. The comet is mildly evolving towards a capital 'D' with the flat side representing the South. Bob Ayers' description is still apt: Beyootiful!

NGC 1491 BN, Pers. 11.3b - Picked up at 62x as a soft, kidney-shaped glow W. of an 11.15 mag star, visible with no filter. The nebula is darkest on the East side, nearest the star, and brightens considerably to the W. A VHT filter provided more contrast, but I couldn't pull out more detail, besides noting that the glow was irregular, not a smooth gradient.

NGC 1513 OC, Pers. - About 2° SW of 1491, and easily seen in the 80mm finder as a bright concentrated patch of stars, This would be a fine binocular object. At 62x shows small strings of stars with dark 'pockets' between them. 3 prominent co-linear stars oriented E-W on the W. side of the cluster.

ACO 347, Galaxy Cluster, Andr. - I looked forward to revisiting this cluster that lies in and around NGC 891, as I hadn't observed it in about a year. Greg came by and we discussed and observed our way through the different fields, each containing 2-4 galaxies, and all within a few arc minutes of each other. There were about 12 galaxies to be teased out, the NGC's being the most prominent puffs of grey, some with faint stellar cores. The UGC, MCG, and ZWG galaxies were generally smaller and fainter. Having a good chart, knowing the field size, and where to look, was key to pulling out some of the dimmer ones. The most fun, though, was to put a 24mm Panoptic in, and frame 891, the dim granddaddy of edge-ons, in the same field as 898, a dimunitive, but distinct, sliver of an edge on about 25' to the SSE. It's an ant/elephant relationship and well worth the visit.

Steve had a great view of 891 fairly late in the evening, showing a ragged edged dust lane bisecting a warm grey glow. I read yesterday that the dust lane itself is 1.5 thousand light years wide. A useful guidepost in this cluster, besides 891, is a prominent 6.7 magnitude star with the designation HIP 11185. It lies about 22' to the SW of 891, and sits at the NW corner of the richest part of the cluster. It is very easy to hop from this star to the East and South to find the other fields. I observed this cluster for the most part at 242x, with a 9mm Nagler, providing an 18' field.

Objects in Andromeda Galaxy: I continued to study this neighbor, and am starting to think of it as the Northern Hemisphere's answer to the Magellanic clouds. Even at 2.5 million light years distance one can pick out a fair amount of discrete catalogued objects. Perhaps not as visually spectacular, but still an interesting chess game to track down these smudges and stellar dots in a field rich with dust lanes, glowing, unresolvable masses of stars, clumps of bright associations and star clouds. It's a good excuse to loiter and study in such a spectacular setting. Visually, M-31 is more than 5x times the width of the Moon. At 242x, you can pan up and down its length 5 or 6 fields and still be hovering over 'downtown Andromeda'.

As Greg put it in the middle of the evening: "I feel like I'm spying on them."

Steve had indicated an interest in revisiting M-31 to see if his current optics allowed him to resolve some of the brighter globulars beyond a stellar point. G1, at 13.7v, is the most obvious object that one can resolve into a patch, with an extended halo around a few arc seconds of a glow. Perhaps there are more. I've been working up charts, cribbing data from such sources as Luginbuhl and Skiff, Hodge's Atlas of the Andromeda Galaxy, and messier45.com, to construct a set of functional field guides at the eyepiece. I handed out copies of some of the charts to Greg and Steve, and we all spent part of our observing sessions exploring this huge, distant neighbor. I logged 7 more objects. Of the globulars I observed, G213, and G229 felt like they were extended in size, or were softer in character from the field stars. Some of the clusters, while quite faint, were obvious extended spots or patches of grey with averted vision. A40 and C410, both exhibited this character, resembling HII regions in 6822.

In re-examining the Hodge Atlas(available online at http://nedwww.ipac.caltech.edu/level5/ANDROMEDA_Atlas/ Hodge_contents.html) and based on some post mortem comments from Steve, It is clear the 'A' designations, the 'stellar associations' are conglomerates of objects. They are readily, if only partially, seen. And what is detectable, may actually be the combined glow of several catalogued objects. Luginbuhl and Skiff's single page labelled photo chart contributes to the confusion in 2 ways. First, the associations that Hodge indicated with an amoeba-like outline, have a mere line pointing at the brightest area of the association. Secondly, they also include magnitudes of several stars who's values are the same as cluster numbers. '156' means mag 15.6, while G156 is a globular. It's easy to get confused. At that point, it's either throw in the towel, or enjoy the ride. The bottom line is: You don't need an atlas to enjoy looking at M-31, as it is just as 'beyootiful' as 17p Holmes. What workng through a catalogue does provide, though, is to make you look harder, longer, and deeper into an amazing, distant object. That's the fun of it.

Globular Clusters in the Fornax Dwarf Galaxy: In searching online catalogs, I stumbled onto some Hodge designated clusters in this dwarf companion to our Milky Way Galaxy. I threw together a chart right before I snuck out of the office mid-afternoon to head up to Lake Sonoma. There are 6 catalogued Globulars that I could find to look for, and I managed to find 4 of them before I simply stopped observing. The irony is that I never even bothered to look for the galaxy itself. I'll save that for next time out. I see that at least 3 tacos, Jamie, Jay, and Bob Czerwinski, have logged the galaxy itself, so the challenge is on. I'll look for a 'lucency' next time out. ;-)

Fornax 2, GC, For. 13.5- This was the first one I found, as it was an easy hop from a prominent group of stars on the West side of the galaxy. Very faint mottled patch forming the S. end of a triangle with 2 stars in the field to the N. and W. Viewed at 242x. Knowing exactly where to look was essential with this object, as it was quite dim relative to the rest of the field.

Fornax 4, GC, For. 13.6- Visible as a faint, mottled patch In the same 18' field as Fornax 6. A fairly bright star forms a triangle with Fornax 4 to the SE and Fornax 6 NNE. Both of these GC's were brighter than Fornax 2.

Fornax 6: Logged as seen, no description written. Revisit!

NGC 1049, GC, For 12.9- About 9' to the N. of Fornax 6, and larger and brighter than 6 and 4.

Steve announced that is was 11:30, and I didn't want to be a complete washout at work the next day, so I started packing up. It is great to get out during the week, but you do have to cut it short to be functional outside of the hobby. Great session, though.

-Bill