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The Shallow Sky

Ringed Saturn Returns in September

Akkana Peck

The second half of this year's Mars opposition brought a surprise to observers expecting to watch the seasonal changes in Mars' hemispheres: there hasn't been anything to see. If you've been squinting at the red planet, wondering what was wrong with your telescope that you couldn't see all the detail the charts suggested you should, there's an answer: a nearly global dust storm has swept Mars, obscuring most details that might have been visible from amateur telescopes. Even spacecraft pictures show little detail. I've been able to see a polar cap most times I look, and sometimes hints of a few dark features like Syrtis Major showing through the dust, but that's about it.

A bit disappointing for Mars observers, but on the other hand it's also interesting. Look at it this way: how often do you get to see such dramatic proof of a major weather event on another planet? Meanwhile, watch it as it races across Sagittarius (passing a few degrees from the Lagoon Nebula around the 9th) and fades dramatically in brightness during the month.

Saturn, the ringed planet, is back in our skies, rising around midnight at the beginning of the September, and two hours earlier by month's end. The rings are noticeably more open than last year; then, I struggled to tell whether the ring tilt was enough that I could see the outer edge of the A ring all the way around the planet, while this year there's no doubt. I confirmed this during a wonderful observing session on the Mt. Wilson 60" telescope, which turns out to be an outstanding lunar and planetary telescope as well as an impressive light bucket for deep-sky objects. The 60" is available for rent by amateur groups; perhaps a group from our club might consider getting together for a night some time. It's well worth it!

Saturn also offers an occultation this month. On September 10 at 4:55 a.m., Saturn disappears behind the bright limb of a third quarter moon, to reappear again at 6:07 a.m. While this is very early for many of us, it might be worth getting up for; a Saturn occultation doesn't happen very often (especially during darkness), and if you've never seen it, the telescopic view of dim ringed Saturn hanging next to the moon is, well, unearthly. It might be worth using a polarizing filter (single, not the crossed double polarizers used for moon observations; you can take the double filters apart to make two single polarizers, and give the other half to a friend) for the reappearance to dim the sky glow from the rising sun. If you absolutely can't stomach 5 a.m., wait until November for the next Saturn occultation (this time in the evening) - and pray for good weather.

If you do get up for the Saturn occultation, check out Venus while you're there. It's a morning object all month, showing a phase near full. Mercury, on the other hand, is visible in the evening, but it's very low in the west at sunset, so it'll be a difficult target to spot, hanging below Spica.

Jupiter follows Saturn by a couple of hours, though the two are gradually drawing farther apart. In addition to great detail in its cloud belts, Jupiter's four Galilean satellites make for good viewing. This year, we should be able to see shadow transits from all four satellites, not just three (last year the tilt of the satellites' orbits were such that Callisto was off-axis and it and its shadow missed the planet).

The outer planets Uranus, Neptune, and Pluto are all still well placed for evening observing. If you're going to try for 14th magnitude Pluto, use a good chart and start as soon as it gets completely dark. The other two are brighter (visible in binoculars) and are visible most of the night. On the 7th, Uranus passes very close to a 7th magnitude orange star; it should be fun to compare colors between the star and green Uranus. I've seen lots of mixed-color double stars, but it's not often that I get to see an orange and green pair right next to each other!

Mail to: Akkana Peck
Copyright © 2001 San Jose Astronomical Association
Last updated: July 19, 2007

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