Closest perigee for the moon this year

Moon, two days before full. August 29, 2012, 10 p.m. EDT.

Isn’t that a whole lot easier to say than “Supermoon”? But seriously, if you want to know what’s happening with this Sunday morning’s full moon, the best article I’ve seen in a while is over at Sky and Telescope’s website.

The moon will appear about 7% larger than the average full moon, because it’s going to be—get this—7% closer to us. 357 061 km, instead of the “average” 384 402 km.

It will appear more than 7% brighter, though, because brightness varies with the square of the distance. So, (384,4022 − 357,0612) / 384,4022 × 100 = 13% brighter.

If the average lunar brightness at full moon is −12.74 magnitudes, then this Sunday’s moon should be about −12.9.

That’s not a whole lot to write home about.

If you want to do the math, go here.

Another point to consider is that it’s the start of summer, so we’re near aphelion, when the earth is as far from the sun as it can get (the actual date of aphelion this year is July 5). That means that the light available for this June’s perigee full moon to reflect back to Earth is slightly reduced from what it could be.

On the other hand, when a supermoon (full moon at perigee) and perihelion (Earth at closest point to Sun) coincide, that’s going to be one bright full moon! (Sort of. Actually, even a 30% difference in brightness is actually not all that noticeable to most people. Our eyes scale so quickly that such a relative difference is nearly imperceptible.) If you’re curious, the next time these three events (full moon, perigee, perihelion) coincide will be January 1, 2018. That year the closest perigee full moon will occur on January 1, and Earth’s perihelion occurs only two days later, on January 3, at 1 a.m.! So mark your calendar!

In the meantime, I’ll stay up late Saturday night with my camera, hoping for clear-ish skies to restart my full moon project, which got waylaid last October.

Here’s where it left off:

Equinox moon with rays


On the morning of the equinox, as I was fruitlessly attempting to capture an image of Mars near the waning crescent moon, I did manage to create a small mystery for myself with the digiscoped image of that crescent moon:

This is Day 25 of the lunar cycle, which means there are only 4 days until new moon, so there isn’t a whole heck of a lot to look at in this picture. From top to bottom, the most prominent features are the sunlit craters Pythagoras and Babbage (the latter has sunken walls and a prominent crater overlying it to the 4 o’clock position), then the vast expanse of the northern Oceanus Procellarum, broken by the crater pair Herodotus and Aristarchus, with the fine wrinkled area called Vallis Schröteri between/above them.

From there we continue south to the lonely Marius (lovely plurivocal name that; if you’ve not seen the Pagnol film, you really ought to, sometime, if you like old French movies), with an equally lonely Reiner to his lower left (SW). Reiner is situated near an interesting albedo feature (bright area) called Reiner Gamma, about which the moon master Chuck Wood has some interesting commentary. (In fact, after starting my research for this post, I noticed that the aforelinked LPOD photo mentions the very mystery feature I was looking up, so click the darn link!)

At the bottom of the vast Oceanus Procellarum is the prominent crater Mersenius, which has a line of what look like mountains leading toward it from the northeast. These “mountains” are unnamed but appear to be part of the wall that surrounds the Mare Humorum, which is in shadow to the east (right).

But what attracted my attention in this snapshot was how bright the left-hand side is. It’s pretty hard to overexpose one part of the moon so much, while leaving the rest of it in relatively decent tonal values. When I zoomed in (click the photo; it’s much better at larger sizes), I discovered that this overexposed region was a result of the bright ray system emanating from the western limb of the moon.

I’d never noticed it before, and the feature responsible isn’t really mentioned in the 1996 edition of the lunar observer’s bible (Rükl’s atlas), although it does appear in that book under the unassuming name Olbers A. Here is the portion of the Lunar and Planetary Laboratory’s Quadrant map of the moon (1964) where the feature appears at far right (click the map for the full-size image, since the blog software helpfully “centers” the picture):

LPL quad map of southern Oceanus Procellarum region (Quadrant 2, detail)

It’s a bit hard to see what I’m talking about from that shot, so here’s a close-up of that close-up (again, click the image):

LPL quad 2 detail showing Olbers A

The IAU, apparently in recognition of the prominent ray system visible under day 25–like illumination, decided in 1993 to give the crater a name of its own, rather than have it be “the closest crater to the already-named Olbers.” The name they came up with was Glushko.

Rükl’s atlas from 1996 must have been prepared without updating to current nomenclature, because despite the fact that this name change dates back to 1993, this 1996  edition (published in 1990 in the author’s native Czech Republic) continued to call it Olbers A. I’m happy to report that the 2004 edition of the Atlas updates the name with the current IAU designation, Glushko.

This crater is rather small (43 km diameter), but it has a prominent sharp rim. You can see just how sharp, and how interesting this crater appears, in this radar image, taken with radar from the famous Arecibo dish in Puerto Rico, with accompanying commentary by Chuck Wood. The melt texture to the north of the crater in that linked photo is really interesting; it shows how dynamic the process of creating the moon’s impact craters really was!

(Easter) Egg Moon

April 18, 2011 Full moon

Having a five-week old in the house guarantees that if you need to be awake at night to do something, say, take pictures of the full moon, you’ve got a pretty good chance. Of being awake, that is. Staying awake long enough to put the baby to sleep, get downstairs and outside with your camera and spotting scope, well, that’s another story. But Sunday night/Monday morning I was able to pull it off, and here is the result:

As usual, click on the image to see a larger version.

I had missed the official moment of full by a good four/five hours, so you can just see a bit of shadow creeping in at top right (north and a bit east). That teeny hint of shadow is the “sunset” line on the moon, the advancing lunar terminator that will bring the Mare Crisium into shadow in a couple of days (see screenshot below of the “current” moon phase, with the sea of crises just entering the shadow–I’m writing this on my lunch break).

The same thing happens in reverse as the “sunrise” terminator sweeps across the new moon bringing Mare Crisium to view when the moon is just a couple of days old.

First in, first out, that’s the moon’s inventory control system.

Here are some screenshots of a few iPad apps I use to help me find my way around the moon. The first is a moon-at-a-glance style view from the MoonPhase app. It shows lots of useful data, including name of this month’s moon (you can choose which naming system you prefer), current (or time-specified) phase, location in zodiac, position in sky relative to your horizon/zenith, rise/set times, and ephemeris for the current or specified time/date:

It’s really quite a lot of data, and very customizable. You can view calendars of upcoming or past moon phases, the whole nine yards.

Another app I use to help me navigate the moon is MoonHD. It shows a zoomable map of the moon with terrain features labeled; you can orient the moon as it appears from your location, or from space, or from an earth telescope; you can overlay a compass that shows the relative positions of the sun and moon (although it always shows only current relative positions, no matter what time/date/illumination you’ve got dialed in):

And, last but not least, there’s MoonAtlas, which I use for its libration calendar:

This one even looks like a good old moon atlas, and the libration calendar helps me be sure I’m orienting the image correctly. For example, reviewing the graph I can see that the northern limb of the moon is tilted nearly 7 degrees toward Earth at the time of full moon, so that’s quite a favorable libration for viewing the north pole. The moon’s longitudinal (side to side) tilt is only about 2 or 3 degrees, though.

These three apps are almost as useful as/maybe more useful than my beloved, and very old-school, Rükl atlas, which is apparently out of print again. But the main apps I use to enjoy the moon are even more old school than that: my brain, my eyes, and my telescope. With those, I can do just about anything; with a digital camera and these brave new world apps, I can add to the experience, but they don’t replace me bringing my sensory and cognitive apparatus into direct contact with the moon’s image in the eyepiece. It’s my thoughts/perceptions/enjoyment of the spectacular nature in the night-time sky that I’m after; the technology is just a way of accessing and enhancing those thoughts, those perceptions, that enjoyment. No matter how good they are (and they’re good–really, really good), nothing beats that immersive experience of Going Outside.

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.

Dog Days Moon (almost)

The moon goes by many different names. Here are the moon names for August according to MoonPhase, one of my favorite lunar apps for my iPod (and iPad, but I’m consulting the iPod version because Someone Who Shall Remain Nameless drained the battery last night and didn’t plug it in so it’s recharging from the wall charger):

  • August (Calendar Month)
  • Dog Days (in Colonial American parlance)
  • Sturgeon (Algonquin, which was the basis for the Farmers’ Almanac moon names)
  • Grain (English)
  • Dispute (Celtic)
  • Wyrt (Medieval wiccan)
  • Lightning (Neo pagan).

Whatever you call it, it happens today at 1:05 p.m. EDT. And as you may recall from previous full moon posts, I don’t like to take clear weather for granted, so I went out last night to shoot the moon. Here is how I found it at 15 hours before full:

Libration was pretty minimal; the eastern limb was slightly turned toward Earth (1 degree past neutral) and the southern limb was tilted our direction by 3 degrees. Not too much “extra” on the face of the moon last night, and there will be even less tonight (a bit more southern limb, but bang on neutral east–west).

If you recall the question of moon names from previous posts, you might like this very good explanation of the two different systems for naming the full moon. That is, whatever actual name you choose to assign to the full moon (Dog Days, Sturgeon, etc.), in whatever tradition (Colonial American, Farmers’ Almanac, etc.), you will be assigning it based on one of two methods: the (straightforward) “monthly” system (in which the full moon of January gets the first name of the system: Winter moon, January Moon, Cold moon, etc.) or the more involved, but much more seasonally consistent “seasonal” method. The seasonal method involves knowing where you are in relation to the solstices and equinoxes. That is, you need to know what season you’re in, so that you can name the moons appropriately over a longer term. For example, December is the “last” month of the calendar year, but the “first” month of the Winter season.

The difference between the two systems shows up most clearly around the solstices and equinoxes. For example, if, like in 2009, there’s a full moon in December after the Solstice, that moon would have the first name in the series in the seasonal system, but the last name in the series under the monthly rules.

And, if you recall, December 2009 posed a problem because there were two full moons! That made it a blue moon month under the monthly system. Under the seasonal system, though, there was no blue moon in December 2009. There was just the last full moon of autumn (December 1) and the first full moon of winter (December 31). Blue moons can only occur in February, May, August, or November in this method, because it’s the third full moon in a season that has four the blue moon. (Remember? I wrote about this earlier. And if that post isn’t readable enough, you can try this one.)

Regardless of which computus you’re using, though, you still need to name your moons. And I like the Colonial American moon names best, so those are the ones I use, for the most part, in these posts. Others prefer the Farmers’ Almanac names. I reproduce a chart from their website with the moon names for 2010. A prize to the person who spots the irony in this table (think November):

Maine Farmer's Almanac moon names for 2010. What's wrong with this picture?

That’s right. The Maine Farmers’ Almanac, the people who originated the seasonal blue moon rule, list November’s moon, the third moon in a four-moon season, as Full Beaver Moon. I assume this is because there are only 12 moons in this calendar year, so they didn’t have an “extra” moon to name?

Getting back to last night’s moon, though, I still want to get to the bottom of this idea of Dog Days moon. If you believe Wikipedia, the “actual” dog days (“the hottest, most sultry days of summer”) arrive at different times of the year depending on latitude and climate, but I’m afraid I’m a bit more traditional than that. I maintain that the best definition of dog days, at least in the Northern Hemisphere, are those 30 to 40 days surrounding the heliacal rising of Sirius, the Dog Star.

To be fair, the Wikipedia article does mention this definition as well, but it relegates it to the “also defined as” ghetto. But to be even more fair, Wikipedia’s notion that the dog days vary by latitude is “right,” but for the wrong reasons! It’s not just that the hottest, most sultry days of summer arrive at different times of the year depending on how far north of the equator you are; the actual heliacal rising of Sirius varies by over a month in the Northern Hemisphere! As a a matter of fact, the heliacal rising of Sirius at my latitude (roughly 26° N) was nearly a month ago, during the so-called Summer Moon! And it was even earlier (July 17) at the latitude of Heliopolis when this idea appears to have originated (now it occurs on August 4 at that latitude, but that’s because thousands of years of precession have changed things).

If we go by the modern definition of dog days as the hottest days of summer, then here in South Florida they can start as early as June (or even May if you’ve just moved to our fair clime), and they don’t end until late September. Even Halloween is pretty hot here; poor little Eric was sweating like a monster in his dinosaur costume two years ago, and he was one hot sweaty little bee last year!

But I digress. As always, here is the gallery of the full moons of 2010:


Holberg, J.B. (2007). Sirius: Brightest Diamond in the Night Sky. NY: Springer.

Summer Moon

It’s been said so often, and not just by those who dabble in astronomy, but perhaps especially often among those who do: patience is a virtue. After waiting up two hours past my normal bedtime for the summer moon to come out from behind the clouds, she finally did:

Last night’s insurance photo, all warm and fuzzy as it is, really isn’t in the same league. Part of the issue, I’m convinced, is that if I’ve already been asleep, I have a much harder time coaxing focus into my eyes. And on a difficult subject like the full moon through a point and shoot camera’s digital viewfinder, having “awake” vision is critical. So, here’s the Summer Moon 2010, taking its rightful place among the moons of 2010:

Success has its compensations: Tonight’s warm and humid night doesn’t seem nearly so awful as last night’s. The night-blooming jasmine smells particularly sweet, but not too cloying; the crickets are chirping pleasantly, not too aggressively. Everything seems brighter and clearer now that the moon has come out from behind the clouds.

Hope you’ve had a pleasant evening as well.

For those who are interested, the moon was officially full at 9:35 p.m., but this is as close to full as one can reasonably hope to catch her; she’s usually rather inconveniently located at the precise moment. Tonight, she was low on the horizon and behind a rather rude thundercloud.

Warm and fuzzy moon

This morning at 2 a.m. it was still over 80 degrees outside, and, it being 2 a.m. and all, I found it hard to focus. Not just mentally. Literally. See the picture below if you doubt me.

Summer Moon, 25 July, 2010, 2:10 a.m. EDT.

Summer Moon, 25 July, 2010, 2:10 a.m. EDT.

What we have here is a fuzzy shot of the Summer Moon, taken on a warm and sleepless night here in south Florida. I only took the shot because I couldn’t get back to sleep after giving Eric his middle-night bottle (he’s sick. again. and needs his comfort food), for fear that tonight’s Summer Moon (9:35 p.m. EDT) would be clouded out or too low on the horizon for me to shoot while I’m still awake, etc. etc. So it’s an insurance shot, with strong hopes for a do-over, although the clouds outside my window right now make me glad I’ve got this one in the image bank, so to speak.

So, a warm and fuzzy summer moon to you all, and I’ll hope for a sharper image tonight.

Full moon for June

Friday night/Saturday morning, I decided to put my 2 a.m. wakeup call* to good use and get a shot of the moon at close to full. Backyard astronomy at its best!

The house is nice and cool these days, thanks to the a/c man and my suddenly light bank account, and the contrast between the cool and dry indoors and the hot and muggy out of doors was intense, even at 2:25 a.m. I thought I’d entered a sauna just by opening the door to the Florida room! There was a deep mist in the air, but not too dense; a few stars were visible overhead. And, playing peekaboo with some higher fluffier clouds, so too was the moon, just five hours before full:

Here’s the technical data from the caption (which you can see if you mouse over the blank area to the right of the image, or if you read the text below):

Moon 5 hours before full, June 26, 2010, 2:28 a.m. EDT. 100% illuminated. Moon age 13d, 19h, 12m.

I’m quite pleased to have gotten any shot of the moon at all, given the cloudy conditions.

The libration was about 5 degrees east (nearly maximal), and 6 degrees north (again, fairly high, but not maximal). You can see about as far around the eastern limb as possible; you can see both the Mare Marginis and Mare Symthii poking their heads around the side:

Again, you can mouse over the white space, or you can read the caption below:

Maria Marginis and Smythii peeking around the eastern limb near maximal elongation, June 26, 2010, 2:28 a.m. EDT.

Or, you can just enjoy the fuzzy pictures. If you want to know the names of the other maria in the picture, they are, from clockwise, Crisium (top center), Undarum (the little teeny patch of darkness just below and right of Crisium), Fecunditatis (with the bright smudge of the crater Langrenus at the right (eastern) side), and Tranquillitatis.

Here’s the gallery of all the full moons in this sequence; only the first full moon of the astronomical year (Winter 2010, which happened in December 2009) is missing. (For the explanation of how the second full moon in the month of December 2009 is actually part of the Winter 2010 moon sequence, and is NOT a blue moon, try this post.)

*Yes, Eric is still waking up at 2 a.m. to enjoy his nightly appetite-destroying bottle.

Full moon for May

Here at long last is last month’s shot of the near full moon. Time, weather, and energy permitting, I’m still committed to posting at least one shot of each month’s full moon in 2010.

Depending on your browser, you can either click on the image, or mouse over the area to the right of the image, in order to see the caption/description. (In my browser, Safari for Mac, clicking on the image brings up a new window with a “full size” version. Full size in quotes, because I reduced it to 1200 pixels wide just to make it easy to upload.) I’m not sure why my photo gallery tool behaves this way, but there you have it. If you’re curious about the caption and can’t find it with your mouse, here it is:

Just past full moon, May 29, 2010. 2:18 a.m. EDT. Moon age 15d, 5h, 12m.

This shot was taken a little over a day after the full moon (which was on May 27 at 2307 UT), but it still looks pretty full. The moon was at about 4 degrees eastern libration, and a little over 3 north. That is, the northern and eastern limbs were tilted very slightly toward us. You can tell the moon was past full, because the upper right corner of the moon is starting to show some shadow.

Interestingly, the shadow is much more prominent in that upper right corner; it seems to peter out shortly after you pass the equator heading south. I’ve not quite figured out the geometry of that, but it’s a fun puzzle. Some of the effect might be due to an optical illusion; the Mare Humboldtianum is in that NE corner, and the shadow from its far wall might be deepening the shadows in that area, while the southern limb, lacking this large uniform feature, isn’t thrown into such high shadow.

Anyone else out there have a better idea?

March’s full moon

Jet lag from a recent trip to India combined with a cloudy night to make the blurry shot below the best one I could get of the full moon closest to the March equinox. Oh, well. Here, for the record, is the full moon from March 30, 2010, at 2:52 a.m.:

now, to compare it to December, January and February’s full moons, so we can see any libration effects:

Ignoring my poor alignment skills, you can see that Mare Crisium in March is much farther from the visible limb of the moon than it was in December. This means that it’s a pretty favorable western elongation; it’s even better to the north. Look how “l0w” Copernicus, with its bright ray system, is; the southern limb of the moon is tilted almost as far away from us as it could get. Had I managed to take a clear image, it might be interesting to see what can be seen way up north, there….

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