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EI2GYB > ASTRO 01.05.23 09:21l 140 Lines 10451 Bytes #999 (0) @ WW
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Subj: This Week's Sky at a Glance, April 28 - May 7
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This Week's Sky at a Glance, April 28 - May 7
By: Alan MacRobert April 28, 2023
FRIDAY, APRIL 28
Ý The Moon, a day past first quarter, shines high toward the south-southwest after dark. It's hanging off the crook of Leo's Sickle. The Sickle is nearly upright, with its open side to the right.
SATURDAY, APRIL 29
Ý Today is Spring Astronomy Day! Here are details and some local public events.
Ý This evening the Moon, always a winner for public telescopic viewing, shines just behind (left of) the handle of Leo's Sickle.
The Moon is roughly equidistant from Regulus and Algieba, the Sickle's two brightest stars. Algieba is a nice telescopic binary at medium to high power: magnitudes 2.1 and 2.4, separation 2.7 arcseconds.
SUNDAY, APRIL 30
Ý Face north just after nightfall, look very high, and you'll find the Pointers, the end stars of the Big Dipper's bowl, on the meridian pointing toward Polaris straight down below. From the Pointers to Polaris is about three fists at arm's length.
MONDAY, MAY 1
Ý On this spirit-infused May Day evening (or so our ancestors believed), look high in the west for Pollux and Castor lined up more or less horizontally. Mars is a third, similar dot below Pollux.
Pollux and Castor form the top of the enormous Arch of Spring. To their lower left is Procyon, the left end of the Arch. Farther to their lower right is the other end, formed by 2nd-magnitude Menkalinan (Beta Aurigae) and then brilliant Capella.
Venus shines below the Arch's right side. And tonight, Venus lies smack between the horntip stars of Taurus to its right and left.
This whole big panorama sinks in the west through the evening.
TUESDAY, MAY 2
Ý The waxing gibbous Moon tonight shines only a degree or two from 3rd-magnitude Gamma Virginis (Porrima) as seen from most of North America. Porrima is a lovely, equal-brightness double star for telescopes: separation 3.3 arcseconds this year, oriented almost north-south.
WEDNESDAY, MAY 3
Ý Now the Moon poses only 2ø or 3ø from brighter Spica.
Ý Arcturus shines high to the Moon's upper left. Turn northwest and look to the right of Venus (by about two fists) for Capella, essentially the equal of Arcturus. If you catch Arcturus and Capella just as the first stars come out, you'll find them standing at the same height above your horizon (depending a bit on your latitude).
Ý And Vega, the Summer Star, the other zero-magnitude equal of Arcturus and Capella, twinkles low in the northeast at nightfall. . . depending on your latitude. The farther north you are the higher it will be. If you're in the latitudes of the southern US, you'll have to wait until a bit later after dark for it to appear.
THURSDAY, MAY 4
Ý Chi Cygni, one of the brightest long-period red variable stars, should be at the brightest of its slow, 13-month cycle around now: probably 4th or 5th magnitude. Look for a new, faint star in the shaft of the Northern Cross. As shown below, Chi ( ? ) forms a long, isosceles triangle with 4.0-magnitude Eta ( ? ) Cygni (the triangle's thin end, its northeast or upper left end) and a 5.1-magnitude comparison star 1ø to Chi's northwest. The triangle points to Gamma ( ? ) Cygni, the center of the Northern Cross.
You can follow Chi's season of fading even farther through the summer and fall using the closeup comparison-star chart, with stars to much fainter magnitudes, in the May Sky & Telescope, page 49.
FRIDAY, MAY 5
Ý Full Moon (exactly full 1:34 p.m. EDT). Look for the Moon rising in the east-southeast about 20 minutes after sunset. After dark it shines in the center of dim Libra, far below Arcturus and lower left of Spica.
Later in the night, watch for Delta Scorpii to rise about a fist to the Moon's lower left, then for Antares to rise less far to Delta's lower left.
Delta is still magnitude 1.7, about as bright as it has stayed since 2011 after brightening suddenly in 2000, then dipping up and down from 2005 to 2010. If anything, it has been showing a very slight, secular trend upward over the last two decades. When will it stop?
Ý A deep penumbral eclipse of the Moon will be visible from eastern Europe, eastern Africa, almost all of Asia, and Australia. Mid-eclipse is at 17:23 May 5th UT. Map and details.
Ý Venus remains at about the same height in the western twilight as it's been for a few weeks, but the horntip stars of Taurus behind it (Beta and fainter Zeta Tauri) are sliding farther below it every day.
SATURDAY, MAY 6
Ý We're almost a week into May now, but wintry Sirius still twinkles low in the west-southwest in late twilight. It sets soon after. How much longer through the spring can you keep Sirius in view? In other words, what will be its date of "heliacal setting" as seen by you?
The farther south you live, the later in the season this will be.
SUNDAY, MAY 7
Ý Summer is still more than seven weeks away, but the Summer Triangle is making its appearance in the east, one star after another. The first in view is bright Vega. It's already visible low in the northeast as twilight fades.
Next up is Deneb, lower left of Vega by two or three fists at arm's length. Deneb takes about an hour to appear after Vega does.
The third is Altair, which shows up far to their lower right after 11 or midnight.
This Week's Planet Roundup
Mercury is out of sight in conjunction with the Sun.
Venus (magnitude -4.2, in easternmost Taurus) is the brilliant "Evening Star" shining in the west during and after dusk. It doesn't set until two hours after complete dark.
Night by night, watch as the horntip stars of Taurus, Beta and fainter Zeta Tauri, slide down on either side of Venus. The planet shines a little below them at the beginning of the week, passes between them on Monday May 1st, then stands increasingly above them as they continue settling downward.
In a telescope Venus is a dazzling little gibbous globe, 66% sunlit and 17 arcseconds in diameter. It's gradually enlarging while waning in phase. It'll be 50% lit by late May and will be a bigger, dramatically waning crescent from mid-June through mid-July.
BTW, forget the Face on Mars. Now there's the Monkey on Venus. With 85,000 volcanos newly mapped on Venus, it had to happen. Wave hi to the monkey up there beyond the twilight.1
Mars is crossing Gemini this week, upper left of Venus by 2 or 2« fists at arm's length. It's much closer below or lower right of Pollux.
Mars has faded to magnitude +1.3, the barest trace fainter than Pollux. Mars also shows a slightly deeper orange tint. It will line up with Pollux and Castor, to their left, on the evening of May 16th.
Mars is nearly on the far side of its orbit from us, so in a telescope it's just a tiny blob 5« arcseconds wide.
Jupiter is lost in conjunction with the Sun.
Saturn (magnitude +1.0, in dim Aquarius) is low in the east-southeast before and during early dawn.
Faint Uranus and Neptune are out of sight, very low in evening and morning twilight, respectively.
All descriptions that relate to your horizon - including the words up, down, right, and left - are written for the world's mid-northern latitudes. Descriptions and graphics that also depend on longitude (mainly Moon positions) are for North America.
Eastern Daylight Time (EDT) is Universal Time minus 4 hours. UT is sometimes called UTC, GMT, or Z time.
Want to become a better astronomer? Learn your way around the constellations. They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope.
This is an outdoor nature hobby. For a more detailed constellation guide covering the whole evening sky, use the big monthly map in the center of each issue of Sky & Telescope, the essential magazine of astronomy.
Once you get a telescope, to put it to good use you'll need a much more detailed, large-scale sky atlas (set of charts). The basic standard is the Pocket Sky Atlas (in either the original or Jumbo Edition), which shows all stars to magnitude 7.6.
Next up is the larger and deeper Sky Atlas 2000.0, plotting stars to magnitude 8.5; nearly three times as many. The next up, once you know your way around, are the even larger Interstellarum atlas (stars to magnitude 9.5) or Uranometria 2000.0 (stars to mag 9.75). And be sure to read How to Use a Star Chart with a Telescope. It applies just as much to charts on your phone or tablet as to charts on paper.
You'll also want a good deep-sky guidebook. A beloved old classic is the three-volume Burnham's Celestial Handbook. An impressive more modern one is the big Night Sky Observer's Guide set (2+ volumes) by Kepple and Sanner.
Can a computerized telescope replace charts? Not for beginners, I don't think, and not on mounts and tripods that are less than top-quality mechanically. And as Terence Dickinson and Alan Dyer say in their Backyard Astronomer's Guide, "A full appreciation of the universe cannot come without developing the skills to find things in the sky and understanding how the sky works. This knowledge comes only by spending time under the stars with star maps in hand."
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