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Looking at Eddington Crater

Unless either a) this is your first visit to my blog <in which case, welcome! How did you hear about it>? or b) you’ve been living in a cave in the Afghanistan mountains for the past 4 years, you’ll know that I’m the Secretary of Kendal’s astronomical Society, the “Eddington Astronomical Society,” and that it is named after the famous astrophysicist Sir Arthur Eddington, who was born here in Kendal in 1882. (If you want to know more about who Eddington was, and did, then you should go down to Kendal Museum to take a look at the ‘Our Amazing Universe!” exhibition there, which features lots of Eddington info and stuff, or you could just see here) .

Eddington is often called “Kendal’s Forgotten Famous Son” (well, he is by me, anyway!) which is a shame because he was extremely accomplished and succesful, and his achievements were honoured by the scientific community in many ways. One of those ways was naming a crater on the Moon after him.

Do a Search about it on the internet and you’d learn that…

The south and southeastern rim of Eddington is almost completely gone, leaving only a few ridges and promontories in the lunar mare to trace the outline of the original crater. As a consequence, Eddington is now essentially a bay in the Oceanus Procellarum. The remainder of the rim is worn and irregular, forming a mountainous arc that is widest in the north. The floor is almost free of craters of significance, with the nearly-submerged crater Eddington P lying in the southeast sector. If the crater once had a central peak, it is no longer evident.

Elsewhere you would read that…

Eddington is the lava-flooded remnant of a lunar impact crater, located on the western part of Oceanus Procellarum. The western rim is attached to the wall of the walled plain Struve . To the east-southeast is the smaller but prominent crater Seleucus. South of Eddington is Krafft .

… but basically Eddington crater is a 125km wide hole in the surface of the Moon, blasted out of it billions of years ago by an asteroid impact. If it was near the centre of the Moon’s disc as seen from Earth it would be pretty impressive, but it’s stuck up in the top left part of the Moon, almost over the edge, so we see it foreshortened, reduced to a small half-ellipse shell of a crater for the few days when it is approached and then passed by the terminator, the line between night and day.

I always make a point of trying to spot the crater at that time, not just because it’s only right to honour the man my town’s AS is named after, but also because it’s a cool-looking crater, I think. Earlier this week, with a gorgeous almost-Full Moon blazing in the evning sky above Kendal Castle,  I got out my trusty 4.5″ reflector, charged up my digital camera batteries, and went on an “Eddington Safari”. I was hoping to get some good pictures of the crater, but was quite resigned to failing to do so, just because pictures I’ve taken in the past haven’t been that impressive. But this time, it was different. This time, I got this…

I was really pleased with that! Then I zoomed in on the crater, took some more pictures, and after ‘processing’ them to clean them up a bit and bring out more detail, got this…

Now, that I was REALLY pleased with, because it shows the structure of the hills and mountains on the northern side of the crater, and also, clearly, shows how the crater has been filled with a tsunami of lava at one point, reducing it to little more than a bay surrounded by a curving range of hills. Yes, very pleased with that!

Amazingly, the next night was clear too, if anything even clearer than the previous night, so I took some more pictures…

Zooming in on/cleaning up that gets you…

… which I was quite ridiculously pleased with! I know it’s never going to win any awards, or be featured on any NASA websites (I’d submit it to Spaceweather.com, but the last 4 images I’ve sent in they haven’t used, and haven’t even been bothered to email me about them so ###raspberry noise### ) but that’s an image I took through MY telescope with MY camera, showing the crater that’s named after an astronomer who was born where I live, so I think I’m allowed to be a bit woo-hoo! about it! 🙂

But taking those pictures got me thinking… what would Eddington look like from other viewpoints? How impressive would it look if you were approaching it – or looking down on it from above – as you orbited the Moon?

I went to the trusty CELESTIA solar system visualisation software program first, and it showed me these views…

… which are ok, I suppose, but nothing Earth- (or Moon!) shattering. What about Google Moon? Could that help?

That’s better! Wow, Eddington would look quite impressive from above! Those mountains are fascinating… What about some other viewpoints..? Again, Google Moon was a great help…

That’s Eddington seen in “close-up”, from low altitude. Again, impressive… but still dull and flat. No shadows, no surface relief, just shades of light and dark, thanks to the limitations of Google Moon and my ageing PC’s prehistoric graphics card. Oh, if only I could see the crater as it would *really* appear, with shadows and vertical relief and everything…! 😦

Of course, my friends at unmannedspaceflight.com came riding to the rescue, by making and sending me far more realistic views of Eddington crater created on their hi-tech machines…

That brilliant view was created by Bjorn Jonsson, who imported data collected by the Japanese KAGUYA orbiter into a software program that allows him to make detailed images of the Moon’s disc. I’m not going to point out where Eddington is, you should all recignise it by now! And look at the beautiful view of Mare Orientale, down at the ‘bottom’ there… just gorgeous!)

Doug Ellison – founder and “Dictator for Life” of UMSF also helped me in my Eddington Quest by sending me this image he had rendered…

Eddington is the lower, and larger, of the two “upside down crescents” near the limb. Lovely lighting on that, thanks Doug!

Next to offer their help was Jason Perry, one of UMSF’s most accomplished image makers, who actually works for NASA. Jason – who works on the Cassini mission, and runs a very popular blog focussing on studies of Jupiter’s volcanic moon, Io – sent me a whole folderful of beautiful renders of Eddington as it would appear from a Moon-orbiting spacecraft. These images really give a good impression of what the crater would look like if you went to the Moon and waited for your orbit to bring it into view…

Fascinating stuff..!

Next in line to help was Mike Howard, a long-time member of UMSF who has revolutionised the way armchair explorers follow the exploration of Mars with his “Midnight Mars Browser” software, that autromatically downloads all the raw images sent back by the twin Mars rovers for space enthusiasts to enjoy drooling over. Mike has recently created another software package, this time a ‘virtual Moon explorer’. “Moon Globe” is a free app for viewing the Moon on the iPhone and iPod Touch. As Mike explains, “It helps identify features – pretty handy if you’re looking through a telescope or binocs. For people who don’t have access to a telescope or binoculars, it gives a sense of what the Moon looks like up close.”

Mike very kindly sent me some screenshots of views of Eddington rendered by Moon Globe, and here are a few of them…

Pretty impressive, don’t you think? If you have an iPhone or an iPod Touch you can download the app and start exploring the Moon yourself. The link for Moon Globe is http://midnightmartian.com/MoonGlobe/

Mike told me that Moon Globe is currently being downloaded over a thousand times a day, which is great news; a lot more people will be exploring and appreciating the beauty of the Moon thanks to Mike’s app!

But what would the crater look like if you flew over it at a really low altitude? What new details would pop into view? Well, in May 1967 the Lunar Orbiter 4 – which was imaging the Moon as part of the preparations for the Apollo Moon landings – took an image of part of Eddington crater…

That’s Eddington, over on the right. That Orbiter image certainly brings home how rugged the mountain range is at the northern “shore” of the flooded bay that is the crater. And if you click on the image you’ll bring up a larger version, on which you will be able to see a rille on the floor of the crater, and other fascinating details too.

So, there it is… Eddington crater, as seen through a small telescope in Kendal, on the computer screens of modern image manipulators and software wizards, and through the camera of a spacecraft that flew over it more than forty years ago. Hopefully the Japanese KAGUYA probe took some images of it before its mission ended, and my fingers are crossed that the latest NASA Moon probe, LRO, has either taken some images or is planning to take some in the future.

I wonder what Eddington himself would have thought of these images? I wonder what he would have thought of being immortalised on the Moon?


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