Night at the 60 on Mt. Wilson

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Night at the 60 on Mt. Wilson


Příspěvek od Myzer »

Tak asi musim priniest na forum nieco co tu naozaj chyba. :o :o :o

Saturday night August 19th, 2006 was a great night at Mt. Wilson. The weather was calm, clear, and warm. The group viewing through the 60"; scope was friendly and interested, and the docent and scope operator were both interested in the program Jeff and I had put together. Not too surprisingly, due to the altitude and field size limitations, our list and the list of suggested items from the docent were a lot alike.

The evening started with Jupiter in twilight. The 60"; has two basic eyepieces for viewing: a 105mm Kellner (240X) and a 55mm Kellner (458X), and we used both during the night. Jupiter was too bright for this viewer, and I figured it would ruin my night vision for 45 minutes, so I passed on seeing it. Other viewers said it was a magnificent sight, though, with color in the bands.

A reading of the night sky brightness showed 19.49, about 2 magnitudes brighter than my usual observing site on Mt. Pinos. The best it got during the night was in the early morning hours, when it reached 19.76, corresponding to a naked eye limiting magnitude of a little better than magnitude 5.6. Accordingly, the 60" never outperformed a good 32-36" in a dark site (except in resolution), but that's nothing to sneer at. Who wouldn't pay to use one of those all night, eh?

Next was M13 in Hercules, or at least the core of M13. The maximum field of view of this scope is only 11', which is smaller than M13, so the entire cluster would not fit into the field of view. The core, however, is quite impressive in a 60" scope. At this time of the night, the 60" was showing some thermal issues (probably heat leaving the dome, mirror cooling, tube construction cooling. etc), there were some seeing-related issues (the hot air still rising from the LA basin) and the 60" was showing some miscollimation (all the star flares went to one side). None of those problems was serious enough to make the image terrible, however.

We scooted over to NGC6207, a nearby galaxy, from M13. N6207 was nice, with a stellar nucleus, bright core, and extended long axis of the oval shape. Of note was that the short axis of the ellipse had more material on one side than the other, implying a cutoff on one side probably due to a dust lane in spiral arms. Impressive.

The next stop was the planetary NGC6210 in Hercules. A quintessential planetary nebula, it had a bright central star surrounded by a bluish (greenish to some) round cloud of high surface brightness. It also had a faint, not-quite-round, outer ring that was a little reddish in color. Very interesting.

Next was a double galaxy, NGC 5953 and NGC 5954 in Serpens. N5953 is the larger and brighter one of the pair, with a stellar nucleus and bright core offset from the center of the long ellipse. Though not quite a tadpole, N5953 defintely had one end significantly longer than the other, so it's likely quite disturbed. N5954 was smaller, fainter, and fairly nondescript except for a superimposed star on one end.

M15 in Pegasus followed, and, like M13, not the entire globular was visible in the field of view. M15's core is a collapsed core, though, so the star density was much higher than M13. This core is packed!

M5 in Serpens was next. This was another globular larger than the field of view, but less so than the others. Additionally, the stars are arranged in circumferential patterns, resembling petals on a rose. Beautiful.

NGC 6543, the Catseye Nebula, a planetary in Draco was next. This was large, bright, bluish, and displayed a complex inner structure resembling two overlapping ovals. I couldn't see this at the lower power (though one woman, complaining about her poor eyesight, could, ha, ha.), but the double structure was obvious at the higher power. There also appeared to be a surrounding outer shell, but it was too faint, and only hinted at with averted vision.

We hopped to T Draconis, a carbon star in Draco. Like many older red giants, there is a lot of carbon in the atmosphere of this star, and it was very, very, red in the eyepiece. It resembled V Hydrae during its down phase. Several shades redder than Antares or Betelgeuse to the naked eye.

M57, the Ring Nebula, a planetary in Lyra, followed. Both the magnitude 15.2 central star and the nearby magnitude 16.2 star were visible on the nebulosity, though the 3rd star on the ring was not. Why? Because the ring was so bright it had visible structure! The ends of the oval were feathered and diffuse, while the narrower sides were brighter and sharply defined. An impressive nebula!

Next was NGC 6905, a planetary in Delphinus. Similar in shape to M57, it is substantially bluer, but has the same diffuse ends and sharp edges of M57. The center is more filled in than M57, yet the central star (mag.15.7) was easier than the central stars in M57.

From there we trudged to Campbell's Hydrogen Star in Cygnus. This appeared like a brilliant blue star with a red "fuzz" around it. Quite a color contrast!!. This is a youngish, Wolf-Rayet, star with incredible instability. Hence the ionization of its surrounding nebula.

M27, a planetary nebula in Vulpecula, followed, but this was a mistake for the small field of view of this scope. Its size was equal or larger to the field of view, but only the short axis of the ellipse, the "Bow Tie" section was visible, and with less detail than it shows in smaller scopes. It was over-magnified and the prominent color visible in 25-30" scopes was absent.

Neptune was next. It showed a featureless, and badly chromatically aberrated disc (due to its low altitude), but Triton was there in the field of view as plain as day. Triton is a very cold moon, almost absolute zero, yet has geysers spewing all over its surface because of the tectonic stress caused by Neptune. We couldn't see the geysers of course, but the startling part of seeing Triton was how far away from the planet it was.

We swung over to NGC 7009 in Aquarius, the Saturn Nebula. This is a large, bright, green-colored, planetary nebula which resembles Saturn because of some "ansae" (ears) that stick out of each end like fuel pods on a jet plane. The central star was bright, and the inner and outer rings showed up quite well, reminding this viewer of a child's gyroscope. There is also evidence of a very faint outer envelope that made the edges of the nebula appear diffuse.

At this point, many people started leaving, and by an hour later our group was down to just 3, so we ecstatically spent more time at the eyepiece as the morning hours progressed.

M71, a globular cluster in Sagitta, quite tidally disrupted because it lies in the disc of the Milky Way, came next. The cluster, and the surrounding field, is incredibly rich with stars. I remarked, and others also saw, that M71 resembled an Angel fish, complete with fins and long tail. Books mention an arrowhead shape, so the extra aperture really brought out a spectacular appearance.

We zoomed over to NGC 7331, a large galaxy in Pegasus. N7331 is usually a stepping stone to nearby Stephan's Quintet (an interacting galaxy group), but the sky was too bright to make that rewarding. N7331 was awesome, though, resembling a miniature M31, with possible dark lanes on one side of a bright core, and long, extending, arms going out both directions from the core. We could make out 5 fainter companions to N7331, 2 of which (N7335, N7337) appeared quite irregular, likely tidally disturbed by NGC 7331.

Next was NGC 7662, the Blue Snowball, a planetary in Andromeda. It lived up to its name, being very blue. The central star was faint, but visible, and the internal structure of the nebula appeared like two oval rings overlaid at 90 degrees from one another. Interesting and complex.

At the scope controller Tom's suggestion, we next viewed the galaxy NGC 7814 in Pegasus. This appears like an almost-edge-on galaxy, with a dark lane cutting it through the middle of its long axis (it resembles a hamburger!). The nucleus is stellar-sized, the dark lane varies in width along its length, and there is definitely more galaxy on one side of the dark lane than the other (the core is offset more toward one side of the lane). This points out the galaxy is not edge-on, but tilted somewhat to our sight. A nice galaxy.

NGC 40 was next, a bright planetary in Cepheus. This planetary had a familiar irregularly bright ring surrounding a fainter inner area, with a bright central star. The outer ring was brighter at two ends and more diffuse at the other two ends (where have you read that before?). The outer ring was bluish, but the inner nebula was reddish. Very interesting. An O-III filter doesn't help the visibility of this nebula; perhaps the red color says why? A picture experiment on this nebula was less than perfectly successful because of shortness of exposure. - Visual deep-sky observing&&Kontakt na Skype: myzer16
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Night at the 60 on Mt. Wilson


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We moved on to Mayall II, the globular cluster also called G1, in the Andromeda galaxy. It was small, faint, but definitely non-stellar. I had to remind myself this cluster was 2.5 million light years away. I'd seen this before, but I remember it being fainter (wonder why?).

We moved to NGC 246 in Cetus, a planetary called "The Skull Nebula". This was so large, the magnification of the 60" made it quite faint, even though it's visible in a 3" telescope. But, adding the O-III filter displayed a wealth of details: a large outer ring (with a few fainter and brighter arcs in the ring), a diffuse inner nebula, and large darker areas resembling eyes. Intriguing, but a little too large for the 60" to show it the best.

M76 (NGC 650/651), the Little Dumbell, a bi-polar planetary in Perseus was next. This one really showed what a 60" can do. WOW! At first, the nebula appeared like a rectangular shape with a slightly pinched middle (like a piece of taffy squeezed in the middle), but closer inspection showed the ends to be of uneven brightness. There was a star off the fainter end and a few faint stars superimposed on the nebula. The brighter end seemed to have a little "hair"coming off one side. An O-III filter showed the rectangle was only the short axis of a large ellipse, with a very faint oval going all the way around. The long axis of the ellipse was easily 2-3 times as long as the rectangle. The "hair" coming off one end of the rectangle was merely the brightest part of the faint outer ellipse. Awesome.

NGC 1275, a galaxy in the heart of Abell 426, a large galaxy cluster in Perseus followed. I suspected we'd see a few galaxies in the 11' field, and I was right. In addition to NGC 1275, a small oval, we saw 9-10 other galaxies in the same field, all at different orientations and subtending different sizes and brightnesses. I've seen many galaxies in this cluster, but the 60', had it seen the entire 1.5 degree-wide cluster, would have seen hundreds.

The galaxy NGC 1032 in Cetus appeared next. This is obviously a disturbed galaxy. It is a near-edge-on spiral, with a dark lane dividing its long axis. The galaxy has more on one end of its bright core than the other (making the core appear off-center), and the other end appears warped (is it tidally disturbed?). Its two companions (the likely culprits) were outside the field of view. Very interesting.

The face-on spiral galaxy, M77, in Cetus was next. The central bar was easy, appearing like a paisley shape with curves on both ends. The center bar was interesting, having a small oval nucleus. The spiral arms formed a fainter round cloud around the bar. My notes: Great! Bright! Large! Awesome!

NGC 1514 was tried, following. This is a planetary nebula in Taurus. Because, like NGC246, it is large, the surface brightness level was low. A couple of us only noticed the nebula as a slight brightening in the field of view: "breath on the eyepiece". But an O-III filter showed the planetary as a very large, flower-shaped, nebula surrounding a bright central star. The color was purplish! The center of the nebula was fainter than the outer edge, giving the center a hollowed-out appearance around the star. Photographs show this to be an optical illusion. When a bright object appears on the retina, it desensitizes the area around it, causing the surrounding area to appear darker. This especially happens with planets, making the surrounding sky appear blacker, and making the appearance of moons easier. N1514 is a nice object. It wasn't on the docent's list, but is now.
[Follow up: at least one photo on the web shows the purplish color and hollowed-out center, so it may not be an optical illusion then. In that case, we were seeing the same image as a longish time exposure photo. Cool.]

Our last object, in the brightening sky of the rising moon, was the center of M42, the Trapezium area of the Orion Nebula (in Orion). Oh My God. I had to pick up my jaw to view this one. The central area of the nebula had the appearance of a hunk of swiss cheese, with a star in each "hole". I'd never seen it like this. 8 stars were visible in the trapezium (or was that 9?), and one of the Trapezium stars is red!. After glancing away from the eyepiece, I realized I'd lost night vision in that eye. How bright does that make the nebula? Though this was only the center of the nebula, and the usual colors were absent due to magnification and field size, this was truly an awesome way to end the night.

The three of us were given a tour of the bowels of the scope by Tom and Gale (thanks!), where we saw the incredibly heavy castings and support structure for the scope. Best of all was the lockers with the names of Hubble, Zwicky, Minkowski, et. al. It really brought home the near one-hundred year history of this scope.

Driving home in the dawn was invigorating, with my mind full of a night's observing. Gale said he used to spend a lot of time with his scope, but had more-or-less given it up. I think I see why.

Don Pensack
Los Angeles
August 2006. - Visual deep-sky observing&&Kontakt na Skype: myzer16
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Night at the 60 on Mt. Wilson


Příspěvek od blackhaz »

Excellent report, thanks!
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