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APOD: Alphonsus and Arzachel (2021 Jul 17)
Posted: Sat Jul 17, 2021 4:05 am
by APOD Robot
Alphonsus and Arzachel
Explanation: Point your telescope at tonight's first quarter Moon.
Along the terminator, the shadow line between night and day, you might find these two large craters staring back at you with
an owlish gaze.
Alphonsus (left) and
Arzachel are ancient impact craters on the north eastern shores of Mare Nubium, the lunar Sea of Clouds. The larger Alphonsus is over 100 kilometers in diameter. A low sun angle highlights the crater's sharp 1.5 kilometer high central peak in bright sunlight and dark shadow. Scouting for potential Apollo moon landing sites, the
Ranger 9 spacecraft returned closeup photographs of Alphonsus before it crashed in the crater just northeast (left) of its central mountain in 1965.
Alpetragius, between Alphonsus and Arzachel, is the small crater with the deeply shadowed floor and overly large central peak.
Re: APOD: Alphonsus and Arzachel (2021 Jul 17)
Posted: Sat Jul 17, 2021 6:28 am
by Steve Randall
Both of these craters seem to have grooves near the northern rim. Alphonsus has several other lesser grooves too. How do we explain the grooves?
Re: APOD: Alphonsus and Arzachel (2021 Jul 17)
Posted: Sat Jul 17, 2021 9:07 am
by wolfie138
i was just comng to ask the same. maybe fractures caused by the impact that have filled w/ dust over time?
Re: APOD: Alphonsus and Arzachel (2021 Jul 17)
Posted: Sat Jul 17, 2021 10:15 am
by XgeoX
Steve Randall wrote: ↑Sat Jul 17, 2021 6:28 am
Both of these craters seem to have grooves near the northern rim. Alphonsus has several other lesser grooves too. How do we explain the grooves?
Those are lunar rilles. The cause of their formation is in dispute. They could be collapsed lava tubes. They could also be tectonic in nature where the crust broke apart under pressure with one side falling or they were pulled apart.
Here are two examples…
There are rilles on mars but they are said to be inhabited…
Eric
Re: APOD: Alphonsus and Arzachel (2021 Jul 17)
Posted: Sat Jul 17, 2021 10:28 am
by JohnD
Both of those are "Rille", a German word for 'groove' that seems to be given a Latin name in the plural, "Rimae", for some reason. They may be straight or more usually 'sinuous'.
There are many rimae on the Moon and other bodies of the Solar System, and many explanations for them, all of which may be true. One of the most prominent on the Moon is Hadley Rille, visited by the Apollo 15 crew, so we probably know more about that than any other. This report summarizes all that is known, and suggests that it is a collapsed lava tube.
https://www.lpi.usra.edu/resources/USGS ... o-0041.pdf
Of different interest is the oblique line above the craters in the ApoD and tangential to Alphonsus. Obscured by later impacts, including Alphonsus, such straight lines have raised suggestions of intellegent intent, especially when seen on Phobos (
https://www.wired.co.uk/article/phobos- ... ry-created) but are the relic of ancient crater chains.
XgoeX jests!
John
Re: APOD: Alphonsus and Arzachel (2021 Jul 17)
Posted: Sat Jul 17, 2021 11:46 am
by De58te
Interesting observation because these two craters are so close together. The larger crater seems to be shallower than Arzachel. The walls of Arzachel appear to be at least twice as tall and if an astronaut were to slip and fall into it he probably couldn't climb out without help, whereas there seems to be a valley on the side of Alphonsus at around 3 o'clock where the astronaut could potentially walk out. Could this be because the larger asteroid hit with a much gentler force and speed, or that it hit with the same force but was originally just as deep but it was filled up with much more molten lava?
Re: APOD: Alphonsus and Arzachel (2021 Jul 17)
Posted: Sat Jul 17, 2021 12:43 pm
by orin stepanek
To me Arzachel seems to have struck when the
moons surface was like a thick gooey paste before
hardening! IMO
Re: APOD: Alphonsus and Arzachel (2021 Jul 17)
Posted: Sat Jul 17, 2021 1:21 pm
by tf1212
Lovely image, but you have it tilted 90 degrees. Northeast is upper right
Re: APOD: Alphonsus and Arzachel (2021 Jul 17)
Posted: Sat Jul 17, 2021 1:22 pm
by tf1212
my error, lower left.
Re: APOD: Alphonsus and Arzachel (2021 Jul 17)
Posted: Sat Jul 17, 2021 1:23 pm
by JohnD
Re: APOD: Alphonsus and Arzachel (2021 Jul 17)
Posted: Sat Jul 17, 2021 1:47 pm
by JohnD
Re: APOD: Alphonsus and Arzachel (2021 Jul 17)
Posted: Sat Jul 17, 2021 3:59 pm
by Fred the Cat
This owl has a nice
supercilium!
Super silly us.
Posted: Sat Jul 17, 2021 5:22 pm
by neufer
https://www.etymonline.com/search?q=supercilious&ref=searchbar_searchhint wrote:
<<supercilious (adj.) 1520s, "lofty with pride, haughtily contemptuous," from Latin superciliosus "haughty, arrogant," from supercilium "haughty demeanor, pride," literally "eyebrow" (via notion of raising the eyebrow to express haughtiness), from super "above" (see super-) + second element akin to cilium "eyelid," related to celare "to cover, hide."
Since cilium is more recent than supercilium, the former can be interpreted as a back-formation to the latter .... If indeed derived from the root *kel- 'to hide', we must still assume that a noun *kilium 'eyelid' existed, since the eyelid can 'hide' the eye, whereas the eyebrow does not have such a function. Thus, supercilium may originally have meant 'what is above the cilium'.>>
Re: APOD: Alphonsus and Arzachel (2021 Jul 17)
Posted: Sun Jul 18, 2021 6:13 am
by Fred the Cat
Well I only used the camera and the skies were a little hazy from our surrounding fires but the moon did reveal some nice detail. Now where was that
owl?
Re: APOD: Alphonsus and Arzachel (2021 Jul 17)
Posted: Sun Jul 18, 2021 12:24 pm
by johnnydeep
Fred the Cat wrote: ↑Sun Jul 18, 2021 6:13 am
Well I only used the camera and the skies were a little hazy from our surrounding fires but the moon did reveal some nice detail. Now where was that
owl?
IMG_1868 (2).JPG
That was from a camera alone? I see from the image data that it was a Canon EOS 80D. What lens did you have and were you zoomed in at all? Did you use a tripod?
Re: APOD: Alphonsus and Arzachel (2021 Jul 17)
Posted: Mon Jul 19, 2021 10:15 am
by JohnD
Several members above have posted images. I see from the FAQ page that image posting is allowed if so enabled for that thread (which clearly has been done) and if that member has the priviledge. May I post images, please?
JOhn
Re: APOD: Alphonsus and Arzachel (2021 Jul 17)
Posted: Mon Jul 19, 2021 10:46 am
by XgeoX
JohnD wrote: ↑Mon Jul 19, 2021 10:15 am
Several members above have posted images. I see from the FAQ page that image posting is allowed if so enabled for that thread (which clearly has been done) and if that member has the priviledge. May I post images, please?
JOhn
With the vast amount you have posted I can’t believe you don’t have that privilege. I have only a 100 posts and I have never had to ask.
Question: do you use the advanced editor and the picture tag?
Eric
Re: APOD: Alphonsus and Arzachel (2021 Jul 17)
Posted: Mon Jul 19, 2021 10:54 am
by JohnD
XgeoX,
I'm looking at the 'Full Editor' now. It has an "Insert Image" button which generates pairs of square backets, with 'img' and '/img' in them.
But pasting anything into the space in the middle gets nothing.
There's something in the FAQ about posting images that are online, not on one's hard disk, but are all the above, and elsewhere, pics online somewhere? EG Fred's Moon pic, which he took himself.
What am I doing wrong?
John
Re: APOD: Alphonsus and Arzachel (2021 Jul 17)
Posted: Mon Jul 19, 2021 11:36 am
by johnnydeep
JohnD wrote: ↑Mon Jul 19, 2021 10:54 am
XgeoX,
I'm looking at the 'Full Editor' now. It has an "Insert Image" button which generates pairs of square backets, with 'img' and '/img' in them.
But pasting anything into the space in the middle gets nothing.
There's something in the FAQ about posting images that are online, not on one's hard disk, but are
all the above, and elsewhere, pics online somewhere? EG Fred's Moon pic, which he took himself.
What am I doing wrong?
John
There are several ways to post images that show up as pictures in posts. The "picture" button gives you the [ img ] ... [ /img ] tags between which you put a url link to an online image. There are also the "img2" and "img3" buttons and tags that are variations of that. I find "img3" most useful because you can include caption text with the image. Just hover over a button to get some format help on how to use it.
Then, for uploading pics from your local PC (or iPad, or smart phone), you can use the often overlooked "Attachments" tab below the full editor text entry frame. I don't recall ever being prevented from posting an image except due to exceeding size restrictions. It is recommended to keep your images below 1 MB if possible
Re: APOD: Alphonsus and Arzachel (2021 Jul 17)
Posted: Mon Jul 19, 2021 11:53 am
by JohnD
AaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaH! The "Attachments" button!! Thank you, johnny!
Just to check, a quick shot by mobile of the half moon in my sky.
JOhn
And it works! I promise not to abuse!
Re: APOD: Alphonsus and Arzachel (2021 Jul 17)
Posted: Mon Jul 19, 2021 12:13 pm
by johnnydeep
JohnD wrote: ↑Mon Jul 19, 2021 11:53 am
IMG_20210716_200810.jpg
AaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaH! The "Attachments" button!! Thank you, johnny!
Just to check, a quick shot by mobile of the half moon in my sky.
JOhn
And it works! I promise not to abuse!
Yes, it worked. But note that this is an 8.3 MP image and will likely be flagged and removed by the moderator(s). Not sure why it even allowed it to be uploaded, but ideally, it should prevent it in the first place.
[ EDIT: oops - never mind. Though the image is indeed 8.3 Megapixels, it's still well under 1 MB in actual size. So, it should be fine. ]
Re: APOD: Alphonsus and Arzachel (2021 Jul 17)
Posted: Mon Jul 19, 2021 2:54 pm
by bystander
JohnD wrote: ↑Mon Jul 19, 2021 10:15 am ...
May I post images, please?
See:
How to post images
While these are instructions for posting to the
Submissions threads, they apply to the rest of the forum as well.
Re: APOD: Alphonsus and Arzachel (2021 Jul 17)
Posted: Tue Jul 27, 2021 11:00 pm
by Fred the Cat
johnnydeep wrote: ↑Sun Jul 18, 2021 12:24 pm
Fred the Cat wrote: ↑Sun Jul 18, 2021 6:13 am
Well I only used the camera and the skies were a little hazy from our surrounding fires but the moon did reveal some nice detail. Now where was that
owl?
IMG_1868 (2).JPG
That was from a camera alone? I see from the image data that it was a Canon EOS 80D. What lens did you have and were you zoomed in at all? Did you use a tripod?
Sorry. I hadn't noticed your question. Had it mounted on a tripod with a shutter release on the Canon. The 55-250mm lens was at its highest magnification.
Re: APOD: Alphonsus and Arzachel (2021 Jul 17)
Posted: Tue Jul 27, 2021 11:10 pm
by johnnydeep
Fred the Cat wrote: ↑Tue Jul 27, 2021 11:00 pm
johnnydeep wrote: ↑Sun Jul 18, 2021 12:24 pm
Fred the Cat wrote: ↑Sun Jul 18, 2021 6:13 am
Well I only used the camera and the skies were a little hazy from our surrounding fires but the moon did reveal some nice detail. Now where was that
owl?
IMG_1868 (2).JPG
That was from a camera alone? I see from the image data that it was a Canon EOS 80D. What lens did you have and were you zoomed in at all? Did you use a tripod?
Sorry. I hadn't noticed your question. Had it mounted on a tripod with a shutter release on the Canon. The 55-250mm lens was at its highest magnification.
Impressive!