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Archive for June, 2009

Boy, this cloudy weather continues ad nauseum, but there was a little break yesterday and it did come just as it began to get seriously dark, so for a couple hours I got to share some quality time with old friends.  The seeing was very good – the transparency, marginally good. But I turned the 120mm refractor immediately to the double-double and with the 5mm Nagler (180x)  had a beautiful, clean, classic split. I just stared. The sight was familiar, but I kept trying to get the numbers straight.

See, between each pair of stars there’s something in the order of 150 astronomical units. That’s roughly 20 light hours. And between the two pairs there’s a much larger gap – variously  stated as two tenths or a quarter of a light year. I’ll accept two tenths. That’s 1,752 light hours. That meant the gap between the two pairs was nearly 900 times as much as the gap between the two stars that make up a pair. It just didn’t seem that much, though,  and I guess if I had been more scientific about it I would have gotten out the reticle eyepiece and tried to measure it.  Maybe I’ll do that some night. But then, if I did so would it mean anything? I tend to assume we’re looking at this system from above or below  – I forget that these pairs of stars are slowly – very slowly – orbiting one another and where they are in that orbit and how that orbit is oriented to us could make them appear closer together than they really are.

All of which is pretty idle speculation on my part, but did move be a bit closer to appreciating the complex system I was seeing.

I wandered on over to M57 for a peek, but as I said, the transparency wasn’t that great – just very steady skies. I decided that I needed to find my way to  a couple objects in Cygnus I’ve never spent much time looking at before.  The first is a binocular triple – Omicron Cygni. This should be a fun challenge for a good night at Allens Pond this summer. Locating the brightest star is pretty easy – it’s fourth magnitude and is in – or near – what I think of as the western wing of the swan.  What I didn’t know until I checked Jim Kaler’s Web site just now was that in viewing these I managed to miss a carbon star nearby (U Cygni). Dang! And the mental image I retain tells me I saw it and didn’t pay close attention, but I have an overall impression of a very red star in the field.  I was using the 32mm Plossl which gives me a comfortable field of more than 1.5 degrees. Didn’t have any appropriate binoculars handy, but judging from the view in the finder, it should be easy to spot two of these stars while the third will be difficult.  And I’ll have to remember to look for U Cygni next time I have a chance.

61_cygni_finder

My next step was to drop a trail of bread crumbs on the way to 61 Cygni. This fifth magnitude star is off the eastern wing of Cygnus and is the fourth closest star in our night sky and the first to have it’s distance from us measured (11 light years) more than 150 years ago. It’s sometimes called Bessel’s Star or Piazzi’s Flying Star – Bessel’s Star because he first measured its distance in 1838 and Piazzi’s Flying Star because he noted how fast it appeared to be moving (partly because it is so close to us) about a half century before Bessel made his measurement. Me – all I wanted was an easy way to find it in a  kind of busy area of the Milky Way and I discovered that it was conveniently at the apex of rwo bright triangles easy enough to pick out in wide field binoculars.  (See the chart to the left  modified from Starry Nights software.)

Funny – the North American Nebulae has always eluded me, yet for some reason with the 120mm on a night with transparency poor, I felt I could see it fairly easily using the 32mm eyepiece in the 120mm refractor. There was a fairly obvious change in background brightness where it should be. So I need to revisit this with that instrument on a better night.

By this time I was getting tired, however, and the clouds were moving in, so I made one final excursion. This time I swung to the western sky where Izar was still very high and in the steady air, very easy to split  – though I really had to crank up the power to get a comfortable view. I used the 2.5mm Nagler giving 360x – well above 60x per inch – but it worked fine which said good things about the quality of the scope, the quality of the eyepiece, and the quality of the night.

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Contrary to all forecast, it was wonderfully clear when I got up at 2:15 am and I didn’t waste any time getting to the observatory and uncorking the 120mm Skywatcher. It stayed clear for 45 minutes, but dewing was severe and by 3:30 I was down to magnitude 2 or 3 skies with plenty of moisture in the air.

Still, the views of the Double Double were terrific – very steady air and a textbook split, even with the 9 mm Nagler – 100X and the 3.5mm Nagler, 257X . In fact, comparing performances of the Naglers and the TV Plossls I concluded I need another set of Naglers. I need to sell stuff and buy Naglers and I suspect what I’ll unload is the zooms and possibly my 22mm Nagler – though I’m not sure that would be a good idea. What I don’t like about it is it is a 2-inch eyepiece. But its performance is very good. Still, I seldom use low power – if I want nice, widefield views I can always swotch tot he 60mm scope.  I really prefer 1.25 inch eyepieces just because they’re less hassle and less weight.

As for the zooms – well, they are functional, but they encourage too much zooming and I find the 3-6mm Nagler zoom only functions if you clamp it in tight. If you don’t, there are issues with the zooming mechanism.  Besides, with everything on manual the wider field of the Naglers is most attractive – and the clean splits I was getting were just as clean from center to edge. Incredible.

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Up shortly after 2 am – skies somewhat clear – dressed, got tea, and was in observatory by 2:30 am using 120mm Skywatcher and my grab ‘n go kit – 32mm TV Plossl, 8-24 Hyperion zoom and 6-3 Nagler zoom.

My first target was Rasalhagethi (Alpha Herculis)  and it showed nicely in the Hyperion zoom, splitting cleanly at 8 and one click-stop above 8. However, it split much better with the 6-3 Nagler zoom. Some flaring of the primary with the  8-24 Hyperion – pure, round star images with 2-3 diffraction rings using the 6-3 zoom. Judging from the drift, secondary is due east of primary.

These two zooms are far from par focal with one another. However, in double star work I can use the 32mm Plossl and go directly to the 6-3 Nagler with little or no refocusing.I was amazed to find this was so.

I was working at my liesure with no targets in mind. Figured I would  check out Gamma Delphinus, then move on to the last quarter moon which was now above my tree line. Gamma split easily – even split at 24mm, but was real nice at 8mm. No flaring with these two more evenly matched stars (4.5 and 5.5). Restored some faith in the  Hyperion zoom. Of course, they are also more than twice is far apart as Rasalgethi.

I was enjoying this when zoom – the clouds came in – in about five minutes it was 80% overcast. So my observing session went simply from 2:30 am to 3:15 am, then I packed up and headed in.

Ah well – given the terrible weather we’ve been having, this was a refreshing little interlude – and for a while the skies were very clear and very steady.

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