Archive for the ‘Moons’ Category


The mountains of the moon, and the moons of Jupiter

February 15, 2012

My latest efforts at white-trash astrophotography (or, if you prefer, afocal projection photography, or digiscoping), wherein I hold my digital camera up to the eyepiece of my telescope and take pictures:

The moon last night, at last quarter. I love this phase because the mountains that form the eastern rim of Mare Imbrium–the immense incomplete circle in the moon’s northern hemisphere–are still catching the light of the setting sun, creating an arc of light in a sea of darkness. Galileo saw the same thing with his 1-inch telescope 403 years ago, and correctly inferred that the lights in the darkness were mountaintops on the moon, catching either the first (when waxing) or last (when waning) rays of the sun, and that therefore the moon was not a perfectly smooth sphere, but a world with similarities to our own.

And, hey, it looks pretty. I like how the arc-of-light-in-darkness motif is repeated by the smaller craters along the terminator to the south of Mare Imbrium.

Jupiter and the Galilean moons, tonight. As with previous efforts (see here and here), this is a composite shot. To get the moons to show up at all, I had to completely overexpose Jupiter,  so this is a combination of two images. The order of the moons from right to left is also, by chance tonight, their order from closest in to farthest out from Jupiter: Io (by itself on the right), Europa, Ganymede, and Callisto. This is only the second time I’ve gotten Jupiter and all four kids in one shot; often one of the little bleepers is off in Jupiter’s shadow.

All photos taken with a Nikon Coolpix 4500 digital camera, Orion Apex 127mm Maksutov-Cassegrain telescope, and Orion Sirius Plossl eyepieces (32 mm for moon, 25 mm for Jupiter and family).


The moon and Saturn tonight

April 19, 2010

It was almost freakishly clear and calm here in Claremont this evening. My friend and fellow blogger Andy Farke came over and we spent some time looking up.  First target was the waxing crescent moon. Here in town, the seeing is often so bad that at anything over 100x, the image looks like it is under a rippling sheet of water. But tonight we were able to push on to 240x with no problems. I’d say the effects of seeing (atmospheric turbulence) didn’t start to be noticeable until 120x and even at 240x it wasn’t a dealbreaker.

Here’s Mare Nectaris and vicinity (click for the larger, unlabeled version). The line of craters formed by Theophilus, Cyrillus, and Catharina is an easy catch in binoculars at this phase. The Altai Scarp is an immense range of cliffs, hundreds of miles long. Mare Nectaris formed as a multi-ringed impact basin, much like the Chicxulub crater from the “dinosaur-killer” asteroid, and the Altai Scarp is the largest surviving stretch of one of the outer rings.

We had a look at Mars, which was a well-defined disc with hints–and only hints–of detail. I suspected the ice cap from time to time, but couldn’t convince myself that I’d really seen it, as opposed to just thinking the disc looked lighter where I know the ice cap ought to be. Still, a whole ‘nuther planet, y’know? Give me a telescope and a world to point it at and I get a little giddy.

The real treat of the evening was Saturn. At 120x it was crisp and jewel-like, but at 240x it was simply astounding. I have never seen so much detail in one of my own telescopes. The photo is by far my best ever for Saturn, but it just doesn’t do it justice, not by a long shot. The whole planet was striped with pastel bands, and we could clearly see the gap between the rings and the planet. The dark band stretching across the disc is the shadow of the rings. Three moons shone out proudly to the left of the rings; Stellarium informs me that they were Dione, Rhea, and Titan, from inward to out. After Andy left I even caught little Enceladus–she of the geysers–between Dione and the rings.

I also cruised over to the globular cluster M3 and it was very nice, a contained explosion of stars. It looked better than I’ve ever seen it, which is saying something since the moon was out. Most DSOs don’t suffer unduly from bad seeing since they are extended and dim to begin with, but globs do. I’m half-tempted to haul out the scope again and have a look at M13, which ought to be up now, but I have to sleep sometime. Good night, and clear skies.

Photos taken with a Nikon Coolpix 4500 digital camera, shooting through an Orion SkyQuest XT10 telescope and Orion Stratus eyepieces.


Galileo Club, Part 3: Callisto in eclipse

November 8, 2009

There were two chances to see a Galilean moon entering or exiting Jupiter’s shadow from California tonight. At 6:22 PM Europa came out of the planet’s shadow, and at 8:50 Callisto went into it. I missed the first one but caught the second one.

I cheated a little bit; in addition to observing the disappearance of the moon at under 20x as required by the rules, I also photographed it at higher magnification in my 6″ reflector.

Now, when I first started observing, there were four little moons, two on each side of Jupiter, and as I watched, the inner one on the right got dimmer and then disappeared. But that requires a little unpacking. If you punch up Jupiter this evening in Stellarium or Celestia (follow the links on the right to download ’em if you haven’t already–they’re free), you’ll see that Callisto was the inner moon on the left as viewed from Earth. It was the inner moon on the right in the telescope because Newtonian reflectors rotate the image by 180 degrees. No big whoop, but if you watch the un-flipped version in Stellarium, the mechanics of the process are a lot clearer.

Callisto eclipse diagram

If you face south to see Jupiter, the sun is off to your right, having just set. That means the shadow of Jupiter forms a cylinder sticking out into space to the left of the planet as viewed from Earth. Since most stuff in the solar system orbits in a counter-clockwise direction* when viewed from above (Earthly north), Callisto must be on the far side of Jupiter from Earth. Callisto came out from behind the planet (1), was briefly visible from Earth, then entered the planet’s shadow (2), and will re-emerge in a little less than two hours (3).

* Neptune’s largest moon, Triton, is a notable exception, and its backward motion indicates that it is almost certainly a captured Kuiper Belt object and not a “true” moon. In fact, it is possible that all of Neptune’s moons are captured objects.

So how did the pictures turn out? Well…the listed time of 8:50 PM turned out not to be the midpoint of the entrance of the moon into the shadow, but the  completion. Which I guess makes sense, but I was prepared to start my observations 10 minutes early and run 10 minutes after. In fact, by 8:40 Callisto was already noticeably dimmer than the other moons, and at 8:50 the show was over. “Noticeably dimmer” in the eyepiece means “almost impossible to photograph”, at least with my setup (Orion XT6 telescope, 25mm Sirius Plossl eyepiece, and Nikon Coolpix 4500 camera). I thought I had missed it completely. My only shot of Callisto this evening:

Callisto 1 - nothing to see

Can’t see it? Neither could I. But I blew out the contrast and look who showed up, if only just:

Callisto 2 - ugly but there

By using that image as a template, I was able to copy, paste, and lightly sharpen my best Jupiter image of the evening, and replace the moon blobs with tiny little brush-dots that approximate their actual size and brightness, to create this much prettier and more representative, but less real, image:

Callisto 3 - too pretty to be real

Jupiter looks lousy compared to previous efforts because I was looking through most of the LA light dome and attendant haze, but still: eat yer heart out, Galileo. One required task down, ten to go!

(If you haven’t bagged a moon eclipse yet, there are still several opportunities this week.)


Galileo Club, Part 2: Jupiter’s Moons in Eclipse

November 6, 2009


Task #4 for the Astronomical League’s Galileo Club:

4. 1612 – Jupiter’s moons in eclipse: The objective is to show that in addition to the moons being occulted by Jupiter, they also travel through Jupiter’s shadow and are eclipsed. Observe and sketch, noting the timing, one of Jupiter’s moons during an ingress or egress with Jupiter’s shadow. Callisto or Ganymede is the most dramatic. Two observations should be done.  One should be close to when Jupiter is at opposition. The second should be done when Jupiter is at quadrature (90 degrees from the sun). Note how close to the planet the moon is when the event occurred. (Editor’s note: At least two observations and timings are required.)

This is one of the ones that needs to be done Real Soon Now, because the eastern quadrature of Jupiter is this coming Tuesday, November 11. After this Jupiter is going to keep heading west and then disappear into the sun’s glare for a while. Western quadrature won’t be for another six months, and then you’ll have to either get up real early or stay up real late to catch it; western quadrature is equivalent in terms of sky position to last quarter moon.

Unless you want to spend all night watching, waiting, and hoping, you’ll want some idea of when to observe to see the entry or exit of a moon from Jupiter’s shadow. So here’s a list of ingressions and egressions for the next week, taken from Sky & Telescope’s Jupiter moon calculator. Sometimes there is an exit with no entrance, because the moon in question went directly behind the planet as seen from Earth; that’s an occultation rather than an eclipse. Everything is listed both by Universal Time (UT), equivalent to Greenwich Mean Time or London time, and Pacific Standard Time (PST). If you live somewhere else, you can look up your offset from UT at this helpful site.

I’ve never watched one of these events so I don’t know how long they take. Probably worthwhile to start observing 15-30 minutes ahead of the stated time and keep watching until you know it’s over. That blows my titular goal of providing things you can do in 10 minutes, but…whatcha gonna do? Feel free to leave a comment if you make a successful observation. Photo borrowed from here.


Saturday, November 7, 2009
18:18 UT (10:18 AM PST), Io exits eclipse by Jupiter’s shadow. Daytime for US.

Sunday, November 8, 2009
02:22 UT (6:22 PM PST), Europa exits eclipse by Jupiter’s shadow.

Monday, November 9, 2009
04:50 UT (8:50 PM PST), Callisto enters eclipse by Jupiter’s shadow. Sunday night in the US!
09:30 UT (1:30 AM PST), Callisto exits eclipse by Jupiter’s shadow.
12:48 UT (4:48 AM PST), Io exits eclipse by Jupiter’s shadow.

Tuesday, November 10, 2009
08:52 UT (12:52 AM PST), Ganymede enters eclipse by Jupiter’s shadow.
12:32 UT (4:32 AM PST), Ganymede exits eclipse by Jupiter’s shadow.

Wednesday, November 11, 2009
07:16 UT (11:16 PM PST), Io exits eclipse by Jupiter’s shadow. Tuesday night in US!
15:40 UT (7:40 AM PST), Europa exits eclipse by Jupiter’s shadow. Daytime for US.

Friday, November 13, 2009
01:46 UT (5:46 PM PST), Io exits eclipse by Jupiter’s shadow. Thursday evening for US, probably too early for PST.


The moon and Jupiter last night

September 5, 2009

Full moon Sept 4 2009

Last night I attended my first meeting of the Pomona Valley Amateur Astronomers, who, you’ll recall, were kind enough to invite me along on their Mt Wilson trip a few weeks ago. The evening’s feature presentation was  on the Juno mission to Jupiter, which is under construction right now. Juno is slated to launch in two years and arrive at Jupiter in 2016 for a year-long observing run. Unlike the Mars rovers, which can be run until they quit, probes to the Jupiter system are deliberately crashed into Jupiter while they’re still functional. This is to avoid having a probe break down, crash land on Europa, and contaminate it with terrestrial microbes.

It was a great talk and I was feeling jovial–and Jovian–when I got home, so I hauled out my 6-inch reflector to have a look at Jupiter. The atmosphere was fairly clear and steady so I got out my camera. My method–holding the camera by hand up to the eyepiece–is called afocal projection photography by photographers and opticians, digiscoping by birders, and white trash astrophotography by me. My camera is an older model, a 4MP Nikon Coolpix 4500, but it has good optical zoom and it is a favorite for this sort of thing among birders.

If you want all the nitty-gritty, I put the camera in macro (flower) mode, manually set the exposure, zoom to the desired level, let the camera autofocus on the target, and snap away. I usually take between 50 and 100 pictures. This gives me a good sample from which to pick the one or two best shots afterward. Sometimes my hand moves, sometimes the autofocus gets squirrelly. The biggest thing, though, is that atmospheric turbulence varies moment by moment. Even on a night when the sky is roiling there may be short windows of stillness, and vice versa, so it pays to take a lot of pictures in hopes of hitting the jackpot. Many people now are using webcams, which shoot continuously, and then choosing only the sharpest images to stack and process. I haven’t ascended to that level yet.

Last night turned out to be exceptional, at least during the brief interval around midnight when I was out shooting. I got the sharpest pictures of the full moon and of Jupiter that I’ve ever taken, and the first I’ve ever gotten of Jupiter with all four Galilean moons. Click the picture below for the full size, unlabelled version (moon IDs from Stellarium). Clear skies!

Jupiter and moons Sept 4 2009 480


Mission 5: Hail to the King

September 2, 2009

Moon and Jupiter Sept 2 2009

Mission Objective: Planet, Moons

Equipment: Naked eye, Binoculars, Telescope

Required Time: 5 minutes

Instructions: Look southeast in the early evening and find the intensely bright star!

The ancients recognized several categories of celestial objects: the Sun and Moon, the fixed stars, transitory and unpredictable phenomena from the commonplace (meteors) to the alarming (comets), and a special category of stars that moved in relation to all the others. The Greeks called this last group the planetes asteres (“wandering stars”) or simply planetoi (“wanderers”), and the term survives little changed to this day.

The ancients could see five wandering stars. Mercury, closest in, swings around the Sun every 87 days, and so was identified with the swift messenger of the gods. Venus, the goddess of love, gave her name to the brightest object in the heavens after the Sun and Moon, the morning and evening star. Blood-red Mars was named, appropriately, for the god of war. Saturn, dimmer than Jupiter and traveling more slowly, was named for the Titan Jupiter displaced, the two-faced god of beginnings and of agriculture.

Was it coincidence that the ancients gave the name of the king of gods to the planet that is, in fact, the largest in the solar system? Possibly not. From Jupiter’s long orbital period they probably deduced that it is very distant from Earth, and yet it is the fourth brightest object in the sky, yielding only to the Sun, the Moon, and Venus. Possibly Jupiter’s stately pace through the heavens was thought more seemly for the king of gods than the frantic Sun-centered scurrying of Mercury and Venus (it would have been obvious, then as now, that the two innermost planets never get very far from the Sun).

If you don’t catch Jupiter in the  early evening, don’t fret. It rises near sunset and will be traveling across the southern sky for much of the night. And tonight, Sept. 2, it will be very close to the moon–as it will be again this time next month. (The moon was on the other side of Jupiter last night, but I was too wound up about Mt Wilson to post this then.) That’s an easy twofer whether you’re using binoculars, a small telescope, or the good ole Mark 1 eyeball.

Speaking of binoculars…just for the purposes of this post, I’m going to assume that you’ve either got a scope and know how to use it, or don’t have one and aren’t going to change that by nightfall. We’ll talk about choosing and using telescopes a lot more in the future, but for now I feel that my advice will have maximum impact for people in possession of binoculars. The pool of people who own a pair of binoculars is huge; the fraction of those people who have used them for stargazing is probably tiny. And Jupiter and the moon are the two celestial objects that benefit most from being viewed with binoculars. So here goes.

First off, don’t worry about what kind of binoculars you have. The 10×50 size is most often recommended for stargazing–at 50mm and above, the objective lenses start to really pull in the faint light for chasing star clusters and nebulae. But the Moon and Jupiter are both crazy bright, so light gathering is not the prime consideration. The prime consideration, as always at this blog, is getting out and seeing something you wouldn’t otherwise. (If you don’t have binoculars but want some, consider these).

Second, the view through steady binoculars is a qualitatively different experience than the shaky hand-held view. There are several ways to hold binoculars steady, but the cheapest (i.e., free), fastest, and easiest is just to brace your elbows against something (top of the car works great for me) or to brace the binoculars themselves against something. My first self-conducted astronomical observation, not quite two years ago, was of Jupiter and its moons, using the humble Tasco 7×35 birding binoculars I’d gotten at Wal-Mart back in high school, leaning up against a street lamp to hold the binoculars steady.

Jupiter in binoculars

What will you see? In even modest binoculars, Jupiter will be a circle, not a point, with between one and four little points of light next to it. The picture above is the simulated binocular view. On one hand, you’re not going to see any detail on the planet. And the four Galilean moons will just be little sparks.

On the other hand–the hand you should be concentrating on–you went to the closet, knocked the dust off whatever binoculars you already had, pointed them at that bright star over there, and now you can see that it is visibly a planet (despite being almost half a billion miles away) and, oh yeah, those little sparks are moons. If you’ve never seen this before with your own eyes, you will have an emotional reaction. Even if you have seen it before, you’ll probably have an emotional reaction. I still do. And usually that reaction is, “Holy BLEEP! That’s BLEEPin’ Jupiter! And its BLEEPin’ moons!” And I want to laugh and cry at the same time, and most of all I want to grab whoever is close and make them look, too. This entire blog is the extension of that feeling.

Jupiter moons by Galileo

You want more coolness still? Using only binoculars, you should be able to sketch the positions of the four Galilean moons over several nights (apparently some Italian yahoo dreamt up this diversion like 400 years ago). Drawing in hand, you can open up Stellarium or pick up the current issue of Sky & Telescope or Astronomy and figure out which moon is which. From inside (closest to Jupiter) out, the four biggest moons are Io, Europa, Ganymede, and Callisto. I remember them like this: vowels (I, E) before consonants (G, C), and both sets in reverse alphabetical order.

Alternatively, you can look up the moons’ positions first, quickly commit them to memory (or draw them, or take the magazine or laptop outside with you), and then when you see them in the binoculars you’ll know that that little spark right there is Io, entirely covered in sulphurous volcanoes, or Europa, whose ice-encrusted oceans are the best possibility for finding life elsewhere in the solar system.

As far as I’m concerned, observing Jupiter in binoculars is both a thrill and a blessing. It’s a moving sight, and it can be the basis of a very accessible and very rewarding observing program (like, er, one of these). It only gets better in a telescope. My 90mm Maksutov shows several cloud belts on clear nights, and occasionally the perfectly black, perfectly round pinpoint of a moon shadow transiting the bright face of the planet. My 6-inch reflector shows more bands and more detail, and so on up from there. BUT, as I frequently say, it’s not about the equipment. It’s about the seeing. And Jupiter is one of the best things out there to see.

If you want the fast facts about Jupiter in an attractive, portable, and free format, check out the IYA2009 presentation about Jupiter. It’s part of the upcoming Galilean Nights event on October 22-24, when amateur and professional astronomers all over the world will set up thousands of telescopes to show the general public the wonders of the heavens.

Oh, one more thing: right after sunset, Jupiter is almost directly below Altair. So if you can find Jove, you can find the Summer Triangle, and vice versa. Get after it!