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Archive for September, 2009

Yeah, east is east and west is west and I sure as hell should know where, exactly, after living in this house for45 years, but I was still caught off guard by the autumal equinox sunrise this morning – well, a bit shy of the equinox, but as I photographed the sun through the trees it had risen a tad and I suspect was just about due east for all practical purposes –  and not where I expected it.

I guess my mind set is more magnetic – that is, magnetic north is about 16 degrees west of true north – so that would make magnetic east about 16 degrees north of true east and while I knew that east was actually a bit south of the magnetic setting, just how much south caught me by surprise this morning.  Turned out if I stand near the door and look over my radio mast to  the southeast corner of the property, then I’m looking due east.  And as I look around thi smatches up nicely with where I see the north star – but I still wasn’t prepared for east being this far “south.”

Sun rising pretty much due east as seen from my upstairs deck on September 19, 2009.

Sun rising pretty much due east as seen from my upstairs deck on September 19, 2009.

Yesterday should have helped, but it didn’t. It was a beautiful morning on September 18, as well,  and we’ve had too few of those in the past several months, so I decided to watch the sunrise and note horizon landmarks fromthe eastern end of the yard, since the sun is just a couple degrees north of east now. First, I checked out Venus.

Venus from Driftway Observatory. The top of the tree comes pretty close to marking east for me. At this point Venus was about 23 degrees up and about as far south of east - 2.5 degrees - as the Sun will north of east 20 minutes later.

Venus from Driftway Observatory. The top of the tree comes pretty close to marking east for me. At this point Venus was about 23 degrees up and about as far south of east - 2.5 degrees - as the Sun will north of east 20 minutes later.

Trees block my view of sunrise from the Observatory area , so I went down to the River (East Branch)  just below us where we have a right of way. There I found two cow pasture cedars that formed a nice sighting device with my neighbors Pt. Jude sailboat and a tree on the eastern horizon about half a mile away.

river_1

And a few minutes after I took the above picture, the sun rose right over that distant tree.

river_sunrise

That river view felt about right to me – but it didn’t seem in sync with what I see from my upper deck – though I trust the Sun is a good indicator  😉

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Watching Jupiter get stripped of its four dancing, Galilean moons last night brought me one surprise even before the event started: With Europa overtaking and passing Ganymede there was a real sense of seeing the planet and its system of moons in three dimensions. That was a genuine rush – one of those feelings that nibbled at the edges of the ineffable – a sudden intuitive grasp  of the enormity of what I was seeing.

This particular route to that feeling was new to me. In astronomy the two-dimensional, flat view dominates because things are just too far away and we are usually looking at them with one eye anyways. Without binocular vision depth is an illusion at best – but still a very interesting illusion.  And I was looking with one eye – but a very good one – my 120mm Skywatcher refractor, which just got a rave review in the latest Sky and Telescope. The review was deserved. This is a terrific scope at any price, but for $1,500 it is fantastic. Add to that a 6mm Ethos eyepiece (150X) and ideal conditions for this relatively rare event – each of the four moons was out of sight at the same time – and all the ingredients were there for a great observing session.

My evening didn’t start that way. I hadn’t intended to observe. I had a full day the next day and I’ve seen the moon’s do their things before – though never all at once – and I was just plain tired. The timing – from near midnight to 3 am was roughly the time when I am usually getting my 4 hours of sleep.  But I went to bed at 9:30, woke up at 10, having had just enough sleep to take the edge off my exhaustion. So I grabbed the 60mm and it’s eyepiece case and headed for the observing deck to see if Jupiter was over my trees. It turned out to be peaking through them – right through the notch between the trees that is due south and so I could see it with the 120mm in the observatory. Great.   I went back, got some tea and my Ipod (nothing like a little musical accompaniment), and came out again to settle into some serious observing.

Skies were both clear and steady – an unusual combination. (When Jupiter was in the trees later I took a quick look at the Double Double in Lyra  and was rewarded by two perfectly split pairs with hard-edged, round stars. Charming – and a sure indicator of steady seeing!) The moon was drowning out any faint stars, so naked eye visibility just bordered on 4th magnitude. I like to experience that from time to time. Gives me a sense of what folks usually see in a light-polluted suburb and I know that’s a lot of the folks I’d like to help learn the night sky. So seeing what they see is handy.

I watched from the observatory until about 11:15. At that point I knew the trees on the west side of my gap were going to cover up Jupiter soon, so I moved out to the observing deck with the Televue 60mm to watch Io and Europa vanish. The view with this scope wasn’t as good, of course, but I could crank it all the way up to 240X with a 2.5mm Nagler and so could easily watch the action. Turned out the observing deck gave me a little more time with my gap in the trees than the Observatory did, but not enough. I was looking for the 11:43 pm occultation of Io and by 11:30 I knew I had to move again, this time to a comofrtable spot outside the observing deck – no problem with the 60mm on its lightweight tripod.  I set up, settled down, and saw the occultation start – I checked my Ipod. Yep – 11:43.  But I had lost the slip of paper where I had written down the time of the next event – the start of Europa’s transit.

Turned out this was 11:58 pm -but  I had in my head it was to be 10 minutes earlier.  Still, I kept watching and waiting and eventually Europa was lost in what seemed to me the light-colored equatorial region of Jupiter. I could not see any trace of it. Meanwhile, Ganymede was making a steady march towards the same general area. But I knew that event was roughly an hour away, so I decided to put the 60mm away and hope the trees had moved enough to allow me to use the 120mm scope in the Observatory.  No luck on that score, which is why I went prowling around Lyra looking for the Double-Double and a few other favorites.  Jupiter remained just out of reach during the time Ganymede was starting its transit. I could see it as I stood at the telescope. The little finder scope on top of the 120mm could “see” Jupiter, but the large scope itself was still being just blocked by the trees and what I saw was a grossly distorted image. Talk about close . . . but no matter. It was beautiful night and I was thoroughly immeersed in it despite the little hassles with trees.  By the time Jupiter popped into the vision of the large scope it was 1 am and Ganymede was gone. (It had started the transit 17 minutes earlier.)

But I had wanted to use the improved resolving power of the large scope to see if I could detect the transiting moons. I couldn’t. What I did see immediately was the sharp black dot of  Europa’s shadow. It was unmistakable, having entered the planet’s disc at 12:56 am.  Also hard to miss, however, were the high stratus clouds covering maybe 60% of the sky and drfiting towards Jupiter.  But I enjoyed looking for detail on Jupiter for another 15 minutes – and watching the progress of Europa’s shadow – and, of course, seeing Jupiter in that rare – moonless – condition.  Eventually the clouds gave me permission to call it a night and get some sleep. Not before, however, I had an opportunoty to reflect on the incredible size/distance examples I had  before me.

Afterall, here was our own, brilliant, 13-day moon glaring just 5 degrees away from Jupiter – about half a fist as I measure the sky. Now the moon is about 3,476 kilometers in diameter. Europa – at 3,120 km a bit smaller, and Ganymede at 5,268km signifcantly larger. Yet, in my telescope I felt good that I could easily tell Ganymede was larger than Europa and both showed discs so tiny that to the casual viewer they looked more like stars than solid bodies. And that, of course, drives home the incredible distance difference. Light takes little more than a second to reach us from our moon. From the moons of Jupiter it was taking more like 30 minutes, the exact time depending on the exact distance of the moment which I don’t know – but one second versus 30 minutes is a ratio of 1,800-to-1. Hmmm . . . and our moon appears to occupy about 30 arc minutes in our sky – that’s 1800 arc seconds – so if we put our moon out at Jupiter it would appear to be labout an arc second in diameter and even Ganymede would be half again that large – 1.5 arc seconds.  Oh, I know this is crude figuring – but I also know it’s in the ball park and is the sort of thing that gives me an appreciation of the larger reality. (Ganymede is actually 1.7 arc seconds when Jupiter is closest to us – Ilooked it up 😉

OK – enough with the left-brained stuff!  In  the final analysis that larger reality – the ineffable feeling – is what I treasure about this evening’s observing  and it doesn’t come out of the numbers. It comes out of being there. It comes out of having the numbers and such in your head somewhere while your senses  deliver the visual experience of the great fan dance that;’s taking place unimaginably far away, and is being carried out by objects whose size and make-up also escape anything I can experience directly – and all with predictable precision. Awesome.

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