SJAA Ephemeris July 2012 | SJAA Home | Contents | Previous | Next

The Shallow Sky

Living in the Past

Akkana Peck


What a great couple of months this has been for shallow sky observers! An annular eclipse, closely followed by a Venus transit – and we got to see both of them, and the weather even cooperated.

I hope all of you had as much fun as I had watching the two events. I went to Red Bluff to be in the annular eclipse path – I’d never seen an eclipse bigger than about 65% before. Dave and I had intended to join a public event at Whiskeytown Lake, but the place was a zoo with no chance of parking anywhere nearby, so we ended up doing some sidewalk astronomy back at our motel parking lot. I’m glad, really – we got to share the eclipse with people who would never have seen it otherwise, and it sure was convenient to be right next to the motel room.

We had fun trying to identify features on the moon’s limb silhouetted against the sun – I think maybe we were seeing that Big Weird Mountain near Mare Orientale (or one of its neighbors), but I never did figure it out for sure. Identifying features on the moon’s limb is always tricky since maps don’t show features like that – and if they did, they’d have to show them at all different librations.

I experimented with different ways of observing the eclipse. I remembered an eclipse when I was a kid where I could see crescent shapes by lacing my fingers together to make a quickie pinhole viewer, or by looking at the shadow cast by the leaves of a tree. Well, the pinhole viewer I made out of a manila folder worked fine to show the sun’s shape – holes about the size of a hole punch worked better than bigger or smaller ones. But that laced-fingers or tree-shadow trick? Those didn’t really show anything until the eclipse was very advanced and the sun had shrunk to a slim crescent. Then suddenly crescent bright spots were everywhere in the shadows. But it would be an unrewarding way to follow the early stages of an eclipse.

I also tried binocular projection. That worked great, though I was using my cheap Big 5 binocular that lacks threads for a tripod mount, and it was fiddly to hold them steady enough to see detail like sunspots. Still, it was very easy to see the shape of the sun even from the beginning stages – a nice cheap solution for folks who don’t have telescopes and can’t locate solar filters in time.

For the Venus transit, I stayed closer to home and used better optics, a Takahashi FS102 with Orion glass solar filter. My primary goal was to see the aureole, the arc of Venus’ atmosphere outside the sun’s disk as Venus began its transit, between first and second contact. It’s also been called the “ring of fire” (though that term does double duty since it applies just as well to the annular eclipse). And indeed I did see the aureole, starting when Venus’ disk was about 2/3 of the way inside the sun’s and lasting until second contact.

There’s been some interesting discussion on the aureole since then on the Shallow Sky mailing list. People saw it in all sorts of filters – Orion, Baader and H-alpha – though the filters that block blue light and show the sun in a deeper orange color may make the effect harder to see. I know I couldn’t see it through a couple of older, orange cast Identi-View filters while I could in the newer, whiter Orion filter, but that could have been telescope size or quality rather than filter color. People saw the effect in apertures as small as 90mm (with a Baader filter) or 40mm (a Coronado PST in H-alpha). Of course, seeing may have been a factor – it was quite windy here in San Jose on transit day.

Nobody I know seems to have caught the aureole in a photo, though I’m sure lots of them will be appearing on the web soon.

Some people reported a bright halo around Venus as it transited the sun, or a 3-D effect on Venus. I didn’t see either of those myself.

Since I’d advised people without telescopes to try binocular projection for the Venus transit, of course I had to try that and make sure I hadn’t given bum advice. It was a lot tougher than binocular projection for the eclipse: I couldn’t hand-hold the binocular steady enough, and I couldn’t see any detail when projecting onto concrete pavement. But when I used an old whiteboard as a projection surface and held the binocular steady on a tripod (I never did get around to rigging up a proper tripod mount), I got a lovely view of Venus in transit, and even some sunspots.

So: lots of ways to see the transit! And it sure did last a long time.

We took a break for a leisurely dinner and still had plenty of time to drive up to Skyline Blvd to find a place to take sunset-with-Venus photos. I loved the sunset views, as the sun squashed orange and red through bands of clouds, looking like a huge Jupiter – complete with a Ganymede shadow transit.

What about this month, July? Well, I guess now I’m living in the past – we don’t have anything in July that comes close to matching the excitement of May and June. But of course the planets and moon are always pretty!

Mercury is visible shortly after sunset for the first half of the month.

Mars and Saturn follow it, Mars setting just before midnight while Saturn lasts about an hour longer. Neither one gets very high.

Uranus and Neptune rise later, about 11 and 10:30 pm respectively, and are available for late-night viewing. Pluto is visible all night, transiting just past midnight, though it’s low in the sky, only 33 degrees, and still mired in that complicated Milky Way field near M22 and M24. Jupiter and Venus are morning objects this month.

So there’s stuff to look at, and of course, the moon and the sun with all those great sunspots will still be there to look at. So even if there are no more world-shattering events, there should be views to keep you and your telescope busy for a while.


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