Archive for the ‘Full moon’ Category


The Rule of Ones

October 19, 2013
C102 2013-10-18

Tonight: one scope, one target. Here’s the scope.

I have several distinct modes as a stargazer. Sometimes I’m in exploration mode and I want to see and log new objects. Sometimes I’m in gear mode and I want to see how a given piece of equipment performs. Sometimes I’m in aesthetic mode and I just want to look at beautiful things. Sometimes I do all three in one night, or even looking at one object.

The last post, about current and future observing projects, was written in exploration mode. “Exploration” might seem like an odd word to apply to the activity of tracking down lists of things compiled by other observers. But if I haven’t seen them myself, then there is still the thrill of the hunt and the rush of discovery. And looking at all of these things is how I personally transmute caelum incognitum into known space. That’s exploration in my book.

Saturday night at the Salton Sea, I was in a blend of aesthetic mode and gear mode, because my ongoing thought process was basically, “Oh, hey, that beautiful thing is up now. I wonder how it looks through these scopes?” I think the only new thing I logged was 8 Lacertae, and if I hadn’t been so close to fiinishing the Double Star program, I wouldn’t have logged any new objects at all, despite staying up almost all night.

I do like observing lists. Some people dismiss them as stamp collecting or say that they make a fun pursuit into work. Well, different strokes, I guess. For me, observing lists come with the implicit subtitle, “Hey, here are the next n-hundred things that are really out there to be seen, any of which might knock your socks off.” Every observing program I have completed has introduced me to new favorite objects, which I periodically revisit, and has broadened my knowledge and experience of the cosmos.

But with all of that said, I don’t do enough casual stargazing, with no plan or agenda. That’s all I used to do, in my first few months as an amateur astronomer, and it almost killed me. Observing programs gave me a way to simultaneously learn the sky and educate myself about what’s up there. But the pendulum may have swung too far now; I hardly ever haul out a scope just to take a quick peek at the moon or Saturn.

All of this is on my mind because of a thread on CN called “When astronomy becomes a chore….” Here’s are some excerpts that have been much on my mind:

RussL: If I feel lazy I can get by with just the 120ST and my trusty TV Widefield 32mm. That way I don’t even have to feel obligated to see each object at every power I can. Easy.

Me: Peace through deliberately limited options–I love it! You have inspired me, sir.

RussL: Well, thanks. I’m glad to know my laziness has helped someone. But, it’s true that sometimes we need to relax more. It’s kinda like when I was a kid with next to nothing to view with, but happy as a clam with whatever I had. I have much more now, although not all that much. I guess part of the difference nowadays is that I have so much more knowledge and feel like I need to use it more. But there’s also a lot to be said for just having a good time without feeling like I must do everything possible.

karstenkoch: I’ve been mentally kicking around an idea for awhile that is still taking shape in my head. For lack of anything better to call it, I’ll call it the “Rule of Ones”. I’ve seen some comments above like it, so I thought I would mention it. There’s really nothing to it other than in order to keep things simple, easy, pure, and enjoyable do or choose only one of everything. Take one scope outside. Take only one eyepiece too. Pick one target to observe. You can imagine all of the other variables involved … choose or do only only one of each. Then, with no more decisions to make, just have a rest under the stars and enjoy your time observing and reflecting.

I like that. One scope, one eyepiece, just go. That sorta dovetails with another idea that has been growing in my mind–more on that in the next post.

Full moon - Oct 18 2013

And here’s the target.


Last week’s full moon

August 5, 2012

Ever since the full moon of January 29, 2010, I’ve been wanting to catch another that was perfectly full. Not a day or even half a day early or late, but right on the button. I came pretty close last Wednesday, August 1. Here’s my best shot, taken with the Nikon Coolpix 4500 shooting through my Apex 127 Mak and 32mm Plossl.

It’s hard to say if this moon is really perfectly full or not; in a way it is, and in a way it isn’t. I know that’s enigmatic, and I’ll clarify it at the end of the post. But first, compare last Wednesday’s full moon to the renowned (by me, anyway) January 29, 2010, moon.

Here, let me make that comparison easier for you. As always, click for the big version.

Two things here are worthy of note. First, there is a difference in illumination. On the left, the east side of the moon is better lit, and on the right, the west.

More importantly, these pictures do not show the same stretch of moon! Check out this overlapped composite, with a few prominent landmarks labelled.

All of the offsets are consistently in the southeast-northwest direction, and the two moons are perfectly overlapped at the periphery. The difference between the images is not because the photographs are rotated in two dimensions, but because the moon was differently rotated in three dimensions. This effect is called libration, and because of it we can see almost 60% of the lunar surface from Earth.

Here’s the comparo again, this time with some of the limb features labelled.

On January 29, 2010, the northwest limb of the moon was tipped toward us, allowing a good view of the “shore” of Oceanus Procellarum and some prominent rim craters like von Braun and its equally-spaced outriders Lavoisier A and Harding. Another useful landmark is the bright crater Seleucus, just to the east of the much larger, dark-floored Eddington. On the opposite limb, Mare Marginis and Mare Australe are barely visible, and Mare Smythii is just a dark patch on the limb itself.

Now compare to last week’s fully moon. The northwest limb is rotated so far away that von Braun is completely lost, along with the rest of the shore of Oceanus Procellarum, and Eddington is a barely perceptible dark streak. On the other hand, the southeast limb shows excellent detail in Mare Australe, especially around the very dark-floored craters Lyot and Oken, and farther north we can see all the way across Mare Smythii to the lighter terrain beyond.

Now, as to the “perfection” of the fullness: there is some terminator-like shadow and detail visible in my  photo from last week, but not on the eastern limb where one might expect it. Instead, all of the visibly shadowed craters are around the south pole. This is where the story gets complicated.

There are three widely-discussed causes of libration: (1) the moon leading or lagging, relative to its own rotation, along its eccentric orbital path; (2) the tilt of the  moon’s axis relative to the plane of its orbit; and (3) rotation of the Earth, which from moonrise to moonset carries an Earthbound observer almost 8000 miles from west to east (which is why everything in the sky rises in the east–that’s the direction we’re constantly headed here on the surface). The moon is only 240,000 miles away, so this daily (or nightly) trip equals 1/30 of the distance from Earth to the moon. How much difference does that make? The average interocular distance for a human is 6.5 cm (2.5 inches), so look at something 30 times farther away (195 cm or just over 6 feet) first with one eye and then with the other. You just simulated diurnal libration.

Now, as I noted above, the eastern limb of the moon is darker than the western side in last week’s photo. The Sky & Tel online almanac said max fullness would be at 8:37 PM, PDT. But the moon was just rising then, about four hours before it would cross the local meridian. In other words, at max fullness the moon was dead overhead for people 4000 miles west of me, but the turning Earth wouldn’t carry me directly under the moon for another four hours–and by the time I got there, it wouldn’t be perfectly full anymore. I took the picture I used in this post at about 11:30–three hours too late for a perfectly full moon. I took other pictures at 8:37 and other times in between, but they turned out poorly–seeing near the horizon was rotten and my scope wasn’t properly cooled yet.

So I’m pretty sure that diurnal libration–the effect of the turning Earth–accounts for the less-than-even illumination from east to west in my moon shot. But that doesn’t explain why there are shadows at the south pole. I assume that the alignment of the moon and Earth was such that I was looking up the moon’s skirts, so to speak–so far south, relative to the moon, that I could see past the illuminated area and into the shadowed highlands beyond. If that’s true, then observers in the Southern Hemisphere, being even farther “below” the moon, should have been able to see even farther into the shadowlands.

The moral of the story is that if you want a good photo of the perfectly full moon, it’s not enough that the moon be visible in the sky at the moment of max fullness–you should also be right underneath it (it should be as high in the sky as it is going to get). Even if you get good enough seeing to get a clean shot of the moon low in the sky, you’ll be several thousand miles to one side or the other, and you won’t be seeing it face-on. On the flip side, if you catch the rising full moon a few hours before max fullness, or the setting full moon a few hours after, you might still get a fully-illuminated disk, because Earth’s rotation will put you along the same line as the incoming light. Sounds a bit hairy, but as Timothy Ferris wrote of making chancy observations, “You can’t catch any fish if you don’t get your line wet.”

Anyway, I had a lot of fun, and got a good look at some southeast limb features that I’d never seen before. I’m anxious to see what libration will bring me next.


A Cheshire Cat on the moon

November 21, 2010

It’s been an interesting week.

I got a new scope…

That was sort of by accident. I really wanted the mount for my 5″ reflector, because it’s a bit too heavy for my current mount and tripod. Orion sells that mount as the VersaGo II for $199, but right now OPT has the SkyWatcher-branded version of that mount, the AZ4, and a nice 80mm refractor with finder and eyepieces for the same price. So by going through OPT I essentially got the scope and accessories for free. I originally planned on selling off the scope, but I keep hearing about people falling in love with the crisp views through refractors (which unlike reflectors and catadioptric scopes have no central obstruction), so I decided I’d give this one a fair shake before I got rid of it.

I’m glad I did. It’s a keeper–it has very sharp optics, gives a nice, clean, contrasty image, and is very fun and easy to use. It doesn’t pull down as much light as my bigger scopes, but it’s easier to handle and it cools down in no time, which is a big plus at this time of year. (One  of the biggest sources of image distortion at the eyepiece is heat waves coming off lenses and mirrors that haven’t reached ambient temperature.) Frequent commenter David DeLano has this scope as well, and he warned me that if I wanted to sell it, I shouldn’t look through it, because I’d get hooked. You called that one right, David!

I gave it a name, too. Some people name their scopes and some people don’t. I also talk to myself and to inanimate objects when I’m alone, and I suspect that those traits are highly correlated with naming scopes. Anyway, there’s a bit of back story behind this one. When I was a kid, my cousin Michael had a good friend, also named Michael, who was quite a bit taller than he was. They felt dumb calling each other by their own name, so my cousin Michael dubbed the taller one “Shorty Long”, and tall Michael retaliated by calling my cousin “Stubby Fats”. That’s never ceased to crack me up. And now I’ve got two shiny black SkyWatcher scopes that will be sharing a mount, one a long skinny refractor and the other a short fat reflector, so it made sense to name them Shorty Long and Stubby Fats.

With the moon and Jupiter both high and bright in the evenings this week, it didn’t pay to go after fainter fare, and I hadn’t put in any serious time on the moon in a long time.

Tuesday the moon was waxing gibbous. I got this shot through Shorty Long with my Coolpix 4500:

It doesn’t show everything there was to see. Sinus Iridium, the Bay of Rainbows, is the C-shape, open to the bottom, at the very top of the moon in the above picture; it’s an old impact basin mostly flooded by the later basalt flows that formed the maria or lunar seas. Just past Sinus Iridium I saw a couple of mountain peaks that the sunlight was just reaching, and they glowed like a pair of eyes staring at me from beyond the terminator. Here, I’ll show you:

Kinda spooky lookin’, eh?

It got better. As I stared back, the rising sun (from the perspective of those mountains) lit a couple of lower peaks, below and between the first two, and then a ridge running beneath all of them. It looked for all the world like the face of the Cheshire Cat, with two bright eyes, two nostrils, and a big wide smile. The nostril peaks and the smile ridge were too faint to show up in any of my photos, but a helpful guy on Cloudy Nights produced this image with the Lunar Terminator Visualization Tool (yay, more free astro software!) using my location and the time of the observation:

One of the nostril peaks was too dim to show up even in the LTVT shot, but other than that the face looks pretty much like what I saw Tuesday night. There is even a suggestion of eyebrows.

The peaks turn out to be the aptly named Harbinger Mountains. I asked around on Cloudy Nights and no one has reported seeing the Cheshire Cat “lunarism” before. I’m going to do a little more research on the features involved and report back.

That wasn’t the end of my weird moon adventures for the week. Last night I was back outside for the full moon:

I had basically just gotten set up when I saw a small, perfectly round object float by in front of the moon. I figured it was probably either a weather balloon or a satellite. Turns out that a CN user got video of the thing; the video is now on YouTube, here.

[Almost Immediate Update: the thing in the video is not the same thing I saw, or at least not the same pass, because that video was made about three hours before I made my observation. I just learned that in the CN thread, which is here.]

It’s probably a satellite; another CN user got video of a similar thing flying in front of the sun, and reports seeing them on a regular basis. So don’t get out your tinfoil hats just yet. But do get out and have a look at the moon when you get a chance. As this week has shown, you never know what you might find, even with this closest and most familiar of celestial objects.


Notes from the underground

September 25, 2010

This is my teaching time of year, and between that and attending a conference in England the week before last, I have had precious little time for observing. But I did get out this week for half an hour to take some pictures of the full moon. Not nearly as detailed and sharp as some of the others I’ve taken in the past, but most of those were taken with 6-10″ scopes, and this was taken with my 2″ SV50.

Now that moon is on the wane, every night will be better and better for observing comet Harley 2, which is cruising through Cassiopeia right now. S&T has a nice page with info on the comet and finder charts. I haven’t looked for it yet, but it’s on my to-do list.

Finally, the fourth installment in my series on the world’s largest telescopes appeared in this month’s PVAA newsletter. This link will be good for the next three months, after which it will be available on the Nightwatch archive site.


January 29th full moon

February 4, 2010

Continuing our all full moon, all the time coverage here at 10 Minute Astronomy, here’s my best full moon photo to date:

You’d think that getting a decent picture of the full moon would be a cinch; after all, it comes around every month. The trouble is, there is a fairly narrow window in which the moon is precisely full (i.e., completely lit from edge to edge), and a couple of days on either side in which it is not-exactly-full-but-close. NEFBC moons look pretty to the naked eye but photographically they elicit pity mingled with contempt: “Ah, I see that you were trying for the full moon there. Bummer, dude.” Most of my previous full moon shots have fallen into that latter category.

The evening of January 29th was just about perfect. For one, the moon reached its fullest when it was centered right over western North America, dead in my sights. It doesn’t matter how still the atmosphere or how good your camera, if the moon maxes out while it’s over Sri Lanka but you’re in California, it’ll be in NEFBC territory by the time it gets to you (or, more accurately, by the time you get to it).

Also, the atmosphere was nice and still. It definitely helped that I was shooting in the middle of the night. When the moon (or anything else) is at its highest point in the sky, you look through the thinnest skin of atmosphere to see it, so there’s less opportunity for bad seeing to spoil the view. Also, by midnight the ground, buildings, roads, and so on have had lots of time to give up their daytime heat, so there’s less stirring of the atmospheric pot.

Also, I cheated, a bit. This is the raw image that came out of the camera:

To get the one at top, I did some fiddling in GIMP (still awesome, still free). First, a light application of Unsharp Mask to punch up the fine details. Be very careful about overusing this one, it is easy to do and oversharpened pictures look worse than raw ones. The biggest giveaway is artificial brightening of any high-contrast boundaries, which in the case of the moon and planets means a ring around the edge. Second, I converted the image from color to grayscale, which keeps the colored pixels from getting tweaked into grossness by the next step. Finally and most importantly, I used Curves to adjust the colors. Curves is sort of like Brightness and Contrast on steroids; you can hold some values constant and brighten or darken other selectively. It is hands down my most used image processing tool.

Feel free to download GIMP and the raw file above and play around. Better yet, get your point-and-shoot camera and binoculars or telescope and take your own moon photos to mess with. If you haven’t seen Mars, it’s not too late, but now that we’re past opposition it’s a little farther away and a smidgen smaller every night. So don’t tarry.


The moon in 3D!

January 27, 2010

Last month I sent in my completed logbook for the AL Lunar Club to Steve Nathan, the coordinator for that club. We struck up a conversation and he shared the above image and some information about it (with permission to post):

The Moon image is attributed to L. M. Rutherford.  The images were take on Sept. 15 and Nov. 13, 1864.  His original negatives were copied by many (!) 3D stereo card publishers for decades…into the early 1900’s.  Other phases of the Moon were also shot in 3D, but all took advantage of the libration effect. Similar 3D images exist for the planets, sunspots, meteors, etc.; all with limited, to no 3D effect. However, somewhere around here I have Neil Armstrong’s famous lunar bootprint…in 3D! (FYI: much of the NASA lunar program photography was done in 3D).  Intriguing, eh?!

If you don’t have a stereo-viewer (I don’t), don’t click on the image (leave it at column width), hold your head back at least a foot and a half from the screen (farther is easier), cross your eyes until the moons double up and then merge the two in the middle to make one bright 3D moon between the two flat ones.

Earlier I had asked if two cameras had to be widely separated geographically to get the stereopair. For making stereopairs of Earthly objects, two photos must be taken with the camera in slightly different places to simulate the separation between our eyes. Since the moon is a quarter of a million miles away, it seemed logical that you’d need the cameras to be as far apart as possible. But as you can read above, the two shots were separated not in space but in time. Steve wrote:

Libration alone will do the trick, the object of interest (the Moon) presents two different views of itself to the observer; increasing the baseline/camera separation would be redundant.

Libration is the “wobbling” of the moon over time as seen from Earth, because of the complex geometry of the Earth/Moon/Sun system. Go here for a more complete explanation.

Pretty darned cool; there is absolutely no reason I couldn’t give this a whirl as soon as the clouds clear out. If I get anything, I’ll post it here. In the meantime, here’s another version of the stereopair that I cleaned up a bit in GIMP. I like the sepia-toned classic version as well; use whichever tickles your fancy.

Finally, many thanks to Steve for sharing the image and the information!