SJAA

Ephemeris

The Shallow Sky in July

Akkana Peck


Mars, still visible in the western sky from sunset to about midnight, is shrinking as it recedes from us. Its disk should be obviously gibbous now in most telescopes; some features should still be visible, but the view won't be as detailed as in previous months. Keep trying, though - you can probably still get good views of the more obvious features, like Syrtis Major, Hellas, Acidalia, and the north polar cap (which is now expanding as the Martian northern hemisphere moves into autumn and the polar cap cools and begins to collect cloud cover.

You can ease your sorrow over the loss of Mars, though, by looking forward to Jupiter's return to our night skies. It's a morning object as the month opens, but by the end of July, the giant planet will rise near midnight, right about the time Mars sets.

And don't miss Venus! During the month of July, Venus' phase changes from roughly half to a slim crescent, as the planet "catches up" to the earth and moves between us and the sun. Watching its phase change over the course of the month should be a nice show in any telescope (and its dance with Regulus through the first half of the month, with the moon joining in to make it a trio on the 15th). As Venus' crescent gets thinner, the planet's apparent size increases, and so does its brightness, at least up until the 14th when it reaches greatest brilliancy at magnitude -4.5. Of course, as its size increases and phase slims, its elevation in the sky will decrease, so it will become harder to find as it sets progressively earlier each day. For a different challenge, try finding it a little before sunset, or even at midday (but of course, be careful not to look accidentally at the sun! It often works well to position yourself in the shade of a building or other large object, so that the building blocks your view of the sun but not of the area where Venus should be). Binoculars help, and a single polarizing filter might be even more help (rotate it until the sky seems darkest in the area where you're looking for the planet).

If you get unusually steady air while looking at Venus telescopically, see if you can see detail in the terminator on Venus, or any markings in the dark side of the planet the ("ashen light"), as some observers have reported.

Neptune reaches opposition on July 26th, in Capricornus. It's low in the sky but should be visible to the persistent binocular user or any telescope user. Uranus, in the same constellation, is also well placed for observing and will reach opposition next month. If you get an exceptionally steady night, try for surface details on Uranus; some observers have reported seeing brown blotches.

Early risers can catch a glimpse of Saturn in the morning sky, about twenty degrees up as dawn begins.

Mercury is too close to the sun to be visible this month.

The third planet reaches aphelion (debate rages on whether this should be pronounced "ap HEE lee on" or "ay FEE lee on"), its farthest point from the sun, on July 6th. It's well placed all month for observing with telescopes, binoculars, or the naked eye, and lots of surface detail should be visible - and you can even observe it in the daytime!


Akkana Peck; last updated: October 04, 2007 Prev Next