October 2012 full moon

October 28. 2012 Full moon

The Hunter’s moon rises nearly or completely full over three successive nights at nearly the same time each night. On Eastern Daylight Time this year, the nights of the 27th, 28th, and 29th, at 5:21, 5:57, and 6:35, respectively. Full moon is today at 3:50 p.m. EDT, but this shot was taken last night right around 10 p.m.

It was relatively far away (402 000 km), and the libration was a little over 4 degrees both east (eastern limb tilted toward Earth) and south (southern limb tilted toward Earth). With the eastern tilt, you can just barely make out the margin of Mare Marginis and Mare Smythii on the right edge (Smythii on the equator, Marginis just north of that), and with the southern tilt, if you follow the “7:30” rays from the bright rayed crater Tycho in the southern hemisphere, you should be able to see—if I’ve worked out the confusing selenography correctly—the dark floors of the large craters Schickard and Schiller. Clavius looks as large as a lunar sea, with the prominent crater Porter in its northern rim:

Southern lunar highlands with prominent features labeled. The only one I’m sure of is Tycho.

I’m having a bit of a problem with the labeling, though. Tycho is obvious. I’m fairly sure I’ve labeled Schickard and Schiller correctly. But if Clavius is that giant area near the south pole that looks almost as big as a lunar sea, something’s wrong. With the southern limb tilted four degrees toward us, I’m surprised to see Clavius looking like it’s on the southern limb. (Then again, four degrees isn’t a huge tilt; when I simulate the view by looking at my awesome new moon globe, it’s hard to make out Clavius way down there on the bottom.)

I’ll have to try again tonight, perhaps with higher magnification.

Here’s the full moon gallery to date; I’ve only missed a couple since December 2009!

The 2012 transit of Venus: astronomical journey


Last Tuesday the second planet from the sun passed in front of the sun’s disk for the second and last time this young century. Back in 2004, I saw the first event briefly while parked outside a gas station trying to get out from under the clouds that had blocked us at our chosen observing site in Florida.

This time, I was pretty sure I could do a better job: a planned trip to relatively cloudless California coincided nicely with the timing of the event, and I had even planned enough time to land, enjoy the customary In-N-Out lunch at the airport, then make the long drive up to our home base (the in-law’s home in Atascadero) with an hour or so to spare before the event began.

Of course, things did not work out as planned. Although I was able to find the binocular filters I’d made years ago out of surplus Baader film, my full-aperture white-light filter made at the same time went missing before the trip. So I needed a last-minute replacement for that.

Here are the binocular filters; although they were made for different binoculars, the loving attention to detail and high-cost materials (cardboard tubes ain’t cheap!) meant I had to recycle them:

For the scope, though, I was in a bit of a fix. Woodland Hills Camera was sold out of “real” filters when I stopped in on the day of the event (gee, supply got outpaced by demand). They did have some black polymer filter material made by Thousand Oaks Optical, which, while not the beautiful white-light image I was used to from the Baader film, was purported to provide a yellow image similar to what the sun “looks like” (that is, what it looks like when you’re not blinded by its brilliance). So I got a sheet of that and went to work.

The staff weren’t particularly helpful in terms of advice and coaching, but they did have the raw materials I needed, and were gracious enough to cede me a corner of their shipping department to assemble the setup: the polymer film for the filter, and a screw-on 77mm camera filter made to fit my little telescope (the TV-60 accepts 77mm filters).  With those, and the cardboard tube I had stuffed into my bag against the possibility of a sold-out store, I had what I needed. A few minutes with scissors and tape, and voila! My new filter was ready!

Then it was just a question of time. The stop at the camera store had put us a bit behind schedule, giving us only 3 hours to make what is, at the best of times, a 3-hour drive. I needed all the help I could get from the traffic gods, and the beginning of the drive was not kind. I had accidentally released the hood catch when I was trying to release the parking brake; a few minutes’ driving at freeway speeds into the strong headwind made it sound like the van was rattling to pieces! We put up with it while I was driving just a few miles per hour above the legal rate, but as we drew closer to home and we realized we had to pick up the pace, it was time to stop and secure the hood. After that it was just a matter of racing headwinds and the traffic (all speeding, but few speeding fast enough to suit my impatience!) trying to find someplace—anyplace!—that would allow an unobstructed view of the sun.

Having completely forgotten the timing of the event, I phoned my father-in-law to get news of when first contact would occur. He diligently researched the matter and informed me that it would happen sometime between 3:03 and 3:06 p.m. PDT. At every stage, I calculated how far we could make it before we had to pull over at a secondary or tertiary site. Gaviota: too far from home to tell. Buellton: too close to call. Santa Maria: 45 minutes away from home at 2:20.

It was a close shave, but we pulled into the driveway at Rancho Atascajoyner around 2:58. Just a few minutes to set up and find the sun, which can be a bit of a trick. I got everything set up fairly quickly, using the borrowed tripod, and miracle of miracles, I managed to find the sun with relatively little difficulty (a feat I was unable to duplicate when I moved the scope to a more comfortable observing position later in the event).

Here’s the setup:

I didn’t have an accurate time signal except for the clock on my Blackberry, but as it turns out, my camera’s clock was relatively well synced with reality: according to that clock, the transit started right around 3:07, and second contact was right around 3:23.

I took many shots with no idea of whether or not the event had started; the first few moments are very subtle, and 60mm is not a lot of resolving power. But here is the moment of first contact, as near as I can determine at 3:07:22 PDT, just a bit later than predicted, but my after-the-fact timing (determined by taking a picture of the time.gov time and adjusting my camera time based on that) could be wrong:

A closer crop of the same picture:

The next image, taken some 92 seconds later, clearly shows the impinging inner planet:

I had no idea how long there would be between first and second contact, so I frantically took picture after picture, checked the sun out with binoculars (I had my Baader binocular filters from the early 2000s) and discovered that it was a good 10–15 minutes (actually 18 or so!) between first contact and complete ingress.

Back in 2004, there had been a lot of talk about the “black drop” effect that made timing the moment of second contact quite difficult; since I wasn’t trying to time it, just take a picture of it, it was a bit easier, but having seriously underestimated the timing, I discovered upon review of the session that I was Very Fortunate Indeed to have captured the moment:

Check out this cropped version to see how hard it is to tell whether Venus is completely free of the sun’s limb (3:23:16 PDT):

Even the next shot, about 20 seconds later (3:23:37, is a bit ambiguous:

Cropped version here:

After the first twenty minutes, this once-or-twice-in-a-lifetime event settles into a rather humdrum routine of checking to be sure the planet’s still in view; it’s not going anywhere for several hours, so split-second timing is no longer necessary. Here’s the view from about an hour after the event started:

So after a 6-hour plane ride, a 4-hour van ride, and a 4-minute setup, I had a very nice view of Venus’s long slow slide across the face of the sun. I had bought three little solar viewers (the TO Optical filter material sandwiched between cardboard layers) for the other spectators, and I made sure that Eric got to see through the telescope, in hopes that his 109-year-old self will remember the view when it happens again in December 2117. Daniel, on the other hand, didn’t seem interested.

Next Mars mission set to depart

NASA’s next Mars mission is set for takeoff. The Mars Science Laboratory (nicknamed, for some insane reason, “Curiosity,” as in what killed the cat) has a launch window that opens tomorrow, November 25, and closes a few weeks from now, on December 18.

This rover is quite a bit bigger than the last set of rovers, Spirit and Opportunity, with a correspondingly more ambitious science mission. But what’s really interesting is the planned landing method: according to the mission website,

The spacecraft will descend on a parachute and then, during the final seconds prior to landing, lower the upright rover on a tether to the surface, much like a sky crane.

That doesn’t sound risky, does it?

It’s also powered by the radioactive decay of plutonium instead of solar panels, so while the power source is more reliable (no dust storms or weather conditions should interfere), it’s also relatively time-definite. Once the plutonium runs out, the mission ends. The science team is coy about the lifespan, calling it only “a full martian year (687 Earth days) or more.” Assuming the rover survives the “sky hook” landing, though, the plutonium-powered mission should be pretty robust, with

 significantly greater mobility and operational flexibility, enhanced science payload capability, and exploration of a much larger range of latitudes and altitudes than was possible on previous missions to Mars.

Here is an artist’s conception of the robot:

Mars Science Laboratory. Image from NASA.

With a planned arrival on the red planet in August 2012, we won’t have long to wait before we find out whether curiosity will be satisfied, or, well… you know the saying about what happened to the cat!

Hunter’s Moon 2011

October 11, 2011 Full moon

October’s full moon this year, the Hunter’s moon, occurred at 10:06 p.m. EDT, about 9 hours before it reached apogee (Oct 12 7:44 a.m. EDT, distance 406 434 km). Local conditions here in south Florida were a bit of a challenge; I had to set up under clouds and hope for a break in the clouds near the time of full moon, which is when I wanted to take the picture. After all, it isn’t often that the moon is exactly full at a convenient time for picture-taking.

Some things fell in my favor: I had completed my field battery over the weekend, so my scope had its larger, more stable and, most importantly, tracking, mount from which to operate. Here’s a picture of the battery setup:

As you can see, it’s on a wheeled cart; those deep-cycle marine batteries are heavy! Some people recommended that I use a LiPo (lithium polymer) battery designed for golf carts and wheelchairs, but I went with the cheaply available Wal-Mart option instead. Having field-tested the weight, I’m thinking those LiPo people weren’t wrong…

This is one heavy battery:

But it does the job, with power to spare (literally—there are two extra cigarette lighter sockets; one for the dew heater and one for a future, as yet unplanned, accessory). The socket strip even has a power switch to prevent accidental draining of the battery:

Even with the best setup, though, you can’t control the weather. There was enough moisture in the air that I never did get a very good shot of the full moon; at “exact” full (10:06), I couldn’t even see the moon from my backyard. This picture is from 9:53 p.m., and is the closest I could come this time around:

If you look at the southern and eastern limbs of the moon, you can see a faint haze; that’s not evidence of an atmosphere on the moon! It’s just photographic evidence of the atmosphere here on Earth!

The moon’s angular size at this point was just under 30 minutes of arc, about as small as it gets, since it was close to apogee, and the second-farthest apogee of the calendar year at that (only March 6, at 406 582 km, was farther).

Like the Harvest Moon last month, the time of the Hunter’s Moon rise over the three nights around full is closer together than at other times of the year: 6:01, 6:33, and 7:08 for my location in Boca Raton; compare that to the situation for March’s full moon, which rose successively at 5:37, 6:44, and 7:52, more than an hour later each night.

Full Moon August 2011

August 12, 2011 Full moon

The full moon for August 2011 (Sturgeon Moon, Dog Days’ Moon, etc.) occurred during the afternoon hours of August 13 (2:57 p.m. to be precise) for East Coast observers, so I did my usual day-before-just-in-case-the-day-after-doesn’t-work photo, and I’m glad I did. The “night” of the full moon, the 13th, was much stormier and less conducive to photos than the night of the 12th, despite the very brief window I had on Friday (only about 5 minutes in the clear).

Here, then, is a snapshot in haste of August 2011’s 18-hours-before-full moon:

You can see how the western edge of the moon isn’t completely “full”; there’s still a little hint of the terminator (sunrise) line over there obscuring that limb; Grimaldi is the last “obvious” crater over there (actually a basin over 200 km in diameter); you can just barely make out some other craters right on the limb, which is angled fairly well away from us at this point by the moon’s libration. It’s a bit odd, because on the eastern limb, you can clearly see Mare Marginis, and Mare Smythii, which is rather far around that side, can also be seen poking its head around, although my libration tables show that it’s only about a 4° E and 4° S libration at this point. I’m not sure why we can see so much of that eastern limb right now. It might just be that the past few years of full moons (since Dec 2009) have had mostly W libration at full, and so even this minimal eastern limb seems extreme to me…

Here’s the complete gallery of full or nearly-full moons; one per month since December 2009.

Lunar eclipse on the solstice


A rare celestial event occurred early this morning, so I thought I’d try my hand at capturing some images. I spent about an hour making sure my telescope mount was as close to polar aligned as I could make it. I balanced the heavy scope on the tube and aligned the spotting scope, the one through which I would be taking the images, with the main scope, so the computerized alignment would proceed smoothly. I took a few practice shots of the full moon about 5 hours before the event would occur:

For some reason I wasn’t able to control exposure as well as I’d hoped; both my “best” practice shots are a bit underexposed, process them as I might:

But I assumed it wouldn’t really matter, since I was probably going to sleep through the first lunar eclipse to occur on the solstice in 456 years, anyway. It had been a long day, and I have a lot of work to do on Tuesday, since it’s my last day in the office before Christmas. And I got a nice shot of the full moon during the September equinox earlier this year, so I’ve had some good luck already with shooting the moon while it’s been in sync with the seasons. Still and all, a lunar eclipse is a pretty exciting event to witness, so it would be nice to have a personal record of it…

Imagine my pleased surprise, then, when my eyes popped open at 3 a.m., and I was able to get dressed and get outside in time to see the first lunar eclipse on the solstice  in 456 years. Without all the prep work, there would have been no chance to capture any images at all. As it is, I got two barely usable shots:

The colors in the image are about as close as I can come to the real thing; I didn’t add any color in postprocessing.

They were both 8-second exposures at f/5.3, shot through a 60-mm spotting scope of 360-mm focal length with a 10-mm eyepiece, yielding 36x magnification.

Busy day on the solstice this year [updated with APOD link]

The December solstice, shortest day of the year is tomorrow, December 21. At approximately 7:38 p.m. EST (2338 UTC), the Sun’s apparent motion in the sky will come to a standstill (Latin, solstitium).* That’s because it has finished its southward migration for the year, and from here until June old Sol will travel north. And as it does so, days in the northern hemisphere will get longer. The image below, from an excellent NASA website, shows the paths of the sun on the longest and shortest days of the year:

 The apparent path of the Sun across the sky.  In summer, the Sun's path is longest, and so are the days. In winter, the Sun's path is shortest, and so are the days. Image from http://www-istp.gsfc.nasa.gov/stargaze/Ssky.htm

The apparent path of the Sun across the sky. In summer, the Sun's path is longest, and so are the days. In winter, the Sun's path is shortest, and so are the days. Image from http://www-istp.gsfc.nasa.gov/stargaze/Ssky.htm

However, the solstice is an event that, while observable on relatively long time scales, is not so interesting to the observer at any given moment. But early tomorrow morning there will be a much more immediately observable event: a total lunar eclipse. The moon is scheduled to be entirely within the earth’s shadow (see image below) between 2:41 and 3:53 a.m. EST: a full 72 minutes of muted glory!

Lunar eclipse geometry, by Fred Espenak

During totality, the southern half of the moon will be much darker than the northern half, as Fred Espenak explains:

From the eclipse diagrams shown earlier, it is clear that the southern (bottom) edge of the Moon will dip much deeper into the Earth’s shadow than will the northern (top) edge. Since Earth’s umbral shadow is darker in the center than at the edge, the Moon’s appearance will likely change dramatically with time as the total phase progresses. A large variation in shadow brightness can be expected and observers are encouraged to estimate the Danjon value at different times during totality (Danjon Brightness Scale). Note that it may also be necessary to assign different Danjon values to different portions of the Moon at different times.

This could be an excellent opportunity for budding astronomers and students to test their observing skills. Try recording your estimates of the Moon’s brightness every ten minutes during totality using the Danjon Scale. Compare your results with your companions and classmates and discover how the Moon’s appearance changes during the total eclipse. The brightness of the totally eclipsed Moon is very sensitive to the presence of volcanic dust in Earth’s atmosphere. As part of a continuing research project, Dr. Richard Keen has been using reports of lunar eclipse brightnesses to calculate a history of optical thicknesses of volcanic dust layers (see: What Will 2004’s Lunar Eclipses Look Like?). If you’d like to help Dr. Keen by making eclipse observations, you can contact him at Richard.Keen@colorado.edu.

Now, as you probably know, lunar eclipses only occur during a full moon. So at midtotality, 3:13 a.m., the last full moon of the year will occur, only 16 hours or so before the official moment of the solstice. When will there be another lunar eclipse during the December solstice? I have no idea.

But to show you how rare even the possibility of such an event is, the next full moon scheduled within 24 hours of the December solstice will take place in 2094. (The last one occurred in 1991.) I read somewhere online that there were only 7 full moons on the December solstice between 1900 and 1999, but I haven’t fact-checked that claim. And I should, because that actually seems like a pretty strong correlation, when you consider that there “should” be only 1 full moon on the solstice every 29.5 years, given that the moon takes 29.5 days to go from full to full. Either the claim is wrong, or my understanding of math is wrong, or both are wrong.

[UPDATE: For an AMAZING pictorial explanation of the event, check out today’s Astronomy Picture of the Day from NASA. The text there answers my speculation above: 456 years since the last solstice eclipse, but no idea when the next will be.]

Jupiter and Uranus tonight

Well, tonight I’m definitely dragging out the big telescope. Jupiter, which I only chanced upon the other day while shooting the moon, is only about 2 degrees from Uranus! I overlooked it, as had dozens of observers prior to Herschel’s discovery of the planet in the 17th century. But now that I’m alerted to its close proximity to its more prominent celestial “neighbor,” I’ll try to take a look tonight. Hope you enjoy your evening!
Don’t expect pictures, although I’ll certainly try; I had enough trouble getting Uranus to come out right…
[UPDATE: As I suspected, Uranus was an underwhelming target, both telescopically and photographically. It was hard even to be sure I was looking at a planet instead of a star, except I could discern, with ever so much concentration, effort, and good will, a glimmer of a disc. And, to be sure, it wasn’t twinkling at all, although the seeing was a bit muddy. Granted, knowing that I was looking at a giant ball of gas halfway across the solar system still made it fun to contemplate, but it wasn’t a spectacle for the eyes; just the brain.
I did manage to get a poor image of Jupiter with a moon (I’m fairly sure it was Io) in shadow transit. At the eyepiece, it was so much more crisp and beautiful than in the snapshot. Near the end of the session you could see the moon emerging on the limb, and it was just astonishing. Of course it doesn’t show up at all in the photograph, but at least you can see the shadow itself:

So it was a fun evening, even if the “results” I have to share aren’t that exciting. Even the lovely wife enjoyed looking at the king of all the planets; her attention was called instantly to the crisp dark shadow of the transiting moon, proving yet again that she’s got the observant eye…]

Full moon and equinox

Two images of last night’s full moon appear below. One was taken a few minutes before the equinox; the other was taken a few seconds after it. Can you tell which is which? (Hint: the moment at which the equinox occurs has no bearing on the appearance of the moon.)

At the time these pictures were taken, the sun was on the opposite side of the earth. The moon was about 6 hours shy of full (which occurred officially at 5:18 a.m. EDT this morning), but close enough that it would take a trained eye to tell that it’s not quite all the way there.

If you look really, really closely at the south polar region, you can see some sharper relief there than elsewhere. And if you compare the two images long enough, you might be able to convince yourself that the second image shows a little bit less relief than the first, but it might just be a trick of the scale (I wasn’t able to get the images to the exact same scale in Photoshop) or of the focus (the second one is slightly “softer” than the first one).

If that’s enough to convince you that the second shot was taken some 15 minutes after the first, bravo! Me, I went by the time stamp in the image metadata.

I stayed up late to get these shots, though, because of what was happening on the other side of the earth at the time: the center of the sun’s disk was crossing an imaginary plane projected up from the earth’s equator. In other words,the equinoctial point was being passed. You might notice that, in the northern hemisphere, the sun will now rise slightly to the south of east, more and more each day. And it will set slightly to the south of west, more and more each day. Until right around December 20 at 11:44 EST, when the center of the sun’s disk will reach about 23.5° S, appear to pause for a little while, and then head back north. This will be the solstice, a word which comes to us from the Latin solstitium, which, loosely translated, means “the sun stands still.”

The sun won’t actually be pausing in its motion, of course, because it isn’t moving. (At least, its apparent motion across our sky is not at all correlated with the direction of its travel through space.) We are the ones moving, and we will have swung around to the point in our orbit where we perceive the sun as reversing its course.

I was motivated to take these pictures because it’s fairly unusual that the full moon falls this close to equinox; the odds of that happening are pretty long. After all, the equinox can happen on any of the 29.5 days of lunation, and there are only two equinoxes a year. Throw in the solstices, and that’s still only four times a year that the moon has a shot at being full at a particularly exciting moment. I’m sure there’s a way to calculate the closest full moon to an equinoctial or solstitial moment, but I don’t know how to do it. Anyone out there know how?

And, as usual with these full moon posts, here are all the full moons of 2010:

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