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A hidden lunar basin on the near side?

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#1 Astrojensen

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Posted 17 November 2019 - 10:41 AM

I was observing the Moon this morning, just before sunrise, at approximately 7.45 A.M. local time (6.45 UT). Instrument used was my 63/840mm Zeiss Telemator with binoviewer with 2x barlow and 25mm Zeiss eyepieces and 32mm plössl eyepieces, giving 67x and 53x, respectively. The sky was very clear, the seeing fairly good, but nothing special. 

 

I immediately noticed something I've never seen before: A large, very low, circular depression with a subtly darker interior in the area between Catharina and Aliacencis, Zagut and Abulfeda, almost centered on the area between Azophi and Sacrobosco. It didn't really command attention to itself, but once spotted, it was impossible to overlook. Very low ridges seemed to go from Gemma Fricius to Aliacencis and from Aliacencis to the unnamed ghost crater west of Playfair and then in a broken chain from the unnamed ghost crater towards somewhere between Almanon and Abulfeda. The region inside these low ridges was consistently slightly darker, just slightly, than the terrain outside it. The eastern side (towards Catharina) was much less well defined, but the albedo differences were easily seen, despite the rugged terrain and maintained a nicely circular shape. 

 

I stopped observing shortly after sunrise, around 8.15 A.M. local time and the feature was still easy to see at 53x. 

 

None of my lunar atlasses showed anything, but Virtual Moon Atlas showed it prominently!! I grabbed a screenshot of the area. Can you spot the feature?

 

gallery_55742_4772_497847.png

 

Here it's marked (roughly):

 

gallery_55742_4772_265243.png

 

 

So, what is it? A true, hidden lunar basin or just a neat coincidence between a lot of ancient, mostly collapsed crater rims? But if the latter, why is the albedo lower inside it in such a nice, circular shape that follows the outline perfectly? 

 

Why have I never heard of this before? 

 

 

Clear skies!
Thomas, Denmark

 


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#2 jeffreym

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Posted 17 November 2019 - 11:10 AM

Thomas,

When I looked at your first image I didn't notice it then after looking at your second image and then going back to the first, it jumps right out!  Nice catch.

Thanks for sharing,

Jeff


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#3 AllanDystrup

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Posted 17 November 2019 - 11:14 AM

I think I've seen an old Pre-Nectarian bassin indicated around this position;

-- have to research that a bit to tell for sure.

 

Allan


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#4 Astrojensen

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Posted 17 November 2019 - 11:32 AM

Thomas,

When I looked at your first image I didn't notice it then after looking at your second image and then going back to the first, it jumps right out!  Nice catch.

Thanks for sharing,

Jeff

In real life, it was easier to see than in the image. It was quite unmistakable, once spotted. Undoubtedly, the binoviewer really helped in spotting it, but it was also visible with a single eyepiece. 

 

 

Clear skies!
Thomas, Denmark


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#5 frank5817

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Posted 17 November 2019 - 11:49 AM

I recall KraterKid (Rich Handy) pointing this out back  around 2007 as looking like an old ring basin.


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#6 Astrojensen

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Posted 17 November 2019 - 12:00 PM

I recall KraterKid (Rich Handy) pointing this out back  around 2007 as looking like an old ring basin.

I thought it was unlikely in the extreme, that no one should have noticed this feature before. Can you find a link to his comment?

 

I can find almost nothing on it online. It is shown in exactly ONE illustration I can find online:

 

lunar-basins.gif

 

It's the smallest, white spot with a black edge, closest to the middle of the Moon in the lefthand image. Image is from this page: http://www.psrd.hawa...unarBasins.html

 

It doesn't appear to have a name, at least that I can find. It might have one, of course, which would probably get more search results.

 

 

Clear skies!
Thomas, Denmark


Edited by Astrojensen, 17 November 2019 - 12:01 PM.

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#7 Tyson M

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Posted 17 November 2019 - 12:33 PM

Nice catch Thomas!

 will try looking for it next lunar outing. 


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#8 Sasa

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Posted 17 November 2019 - 05:59 PM

Interesting finding Thomas. It is amazing what can such humble aperture reveal. Some time ago I was reporting here similar kind of personal unexpected discovery of three domes near Lansberg D that I made with Telementor as well.

https://www.fzu.cz/~..._Telementor.pdf

Edited by Sasa, 18 November 2019 - 12:23 PM.

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#9 John_Moore

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Posted 17 November 2019 - 06:15 PM

You have a good eye, Thomas...I think that it might be the Werner-Airy basin (named by Don Wilhelms). It hasn't the official IAU stamp on it yet, but you never know in the future. The below image is from the Clementine Lidar altimeter data texture, and the central coordinates are Lat 24.0S, Long 12.0 E, with a diameter of ~ 500 km.

 

Of course, the central part of this possible basin looks more convex than concave (which would be expected), however, this material in the inner 500 km diameter ring regions might just be ejecta deposits from other large impacts (e.g. the Nectaris basin), or other basin-forming events nearby and afar (they don't seem to have that dark-ish look to the lava materials as seen in the general Maria).

 

John Moore

 

Normal Werner Airy Basin LIDAR

Edited by John_Moore, 18 November 2019 - 03:30 PM.

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#10 Astroman007

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Posted 18 November 2019 - 09:20 AM

Nice catch Thomas!

 will try looking for it next lunar outing. 

Same here!



#11 Astrojensen

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Posted 18 November 2019 - 11:35 AM

You have a good eye, Thomas...I think that it might be the Werner-Airy basin. It hasn't the official IAU stamp on it yet, but you never know in the future. The below image is from the Clementine Lidar altimeter data texture, and the central coordinates are Lat 24.0S, Long 12.0 E, with a diameter of ~ 500 km.

 

Of course, the central part of this possible basin looks more convex than concave (which would be expected), however, this central material might be ejecta from other large impacts (e.g. the Nectaris basin to the east, or others afar etc.,) nearby.

 

John Moore

 

It matches the observed location perfectly, so that must be it. 

 

Now, who first discovered it and by what means? 

 

 

Clear skies!
Thomas, Denmark



#12 AllanDystrup

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Posted 18 November 2019 - 12:11 PM

It matches the observed location perfectly, so that must be it. 

Now, who first discovered it and by what means? 

Clear skies!
Thomas, Denmark

 

     Several (presumed) pre-Nectarian basins and craters have been described by the USGS in the geological stratigraphic surveys and analysis in the post Apollo decade (mid 1980'ies), -- among these the basins Werner-Airy (which you observed) and Mutus-Vlack in the South-Central nearside highlands.

 

    As John Moore noted, these features are generally heavily subdued and modified by later deposits from Nectarian and Umbrian impacts, so they can be hard to identify.

 

    I have started a Lunar observing project, so I may have some observation reports to share eventually (if we ever get some clear skies again here in Denmark... undecided.gif ).

 

     -- Allan


Edited by AllanDystrup, 18 November 2019 - 01:31 PM.

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#13 Astrojensen

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Posted 18 November 2019 - 02:08 PM

I wonder if the Werner-Airy basin is much easier to detect, when the Moon is waning, than when it's waxing? My observation seems to suggest this.

 

Edit: It might be easier to detect at waning phase, but it's apparently easy enough to see at waxing phase, once you know what to look for. I can easily see it in Thierry's two images in this post: https://www.cloudyni...-3#entry8415192

 

Incidentally, both shots were taken with another 60mm, a Takahashi FS-60.

 

 

Clear skies!
Thomas, Denmark


Edited by Astrojensen, 18 November 2019 - 03:14 PM.

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#14 Daniel Mounsey

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Posted 20 November 2019 - 05:20 PM

I was observing the Moon this morning, just before sunrise, at approximately 7.45 A.M. local time (6.45 UT). Instrument used was my 63/840mm Zeiss Telemator with binoviewer with 2x barlow and 25mm Zeiss eyepieces and 32mm plössl eyepieces, giving 67x and 53x, respectively. The sky was very clear, the seeing fairly good, but nothing special. 

 

I immediately noticed something I've never seen before: A large, very low, circular depression with a subtly darker interior in the area between Catharina and Aliacencis, Zagut and Abulfeda, almost centered on the area between Azophi and Sacrobosco. It didn't really command attention to itself, but once spotted, it was impossible to overlook. Very low ridges seemed to go from Gemma Fricius to Aliacencis and from Aliacencis to the unnamed ghost crater west of Playfair and then in a broken chain from the unnamed ghost crater towards somewhere between Almanon and Abulfeda. The region inside these low ridges was consistently slightly darker, just slightly, than the terrain outside it. The eastern side (towards Catharina) was much less well defined, but the albedo differences were easily seen, despite the rugged terrain and maintained a nicely circular shape. 

 

I stopped observing shortly after sunrise, around 8.15 A.M. local time and the feature was still easy to see at 53x. 

 

None of my lunar atlasses showed anything, but Virtual Moon Atlas showed it prominently!! I grabbed a screenshot of the area. Can you spot the feature?

 

gallery_55742_4772_497847.png

 

Here it's marked (roughly):

 

gallery_55742_4772_265243.png

 

 

So, what is it? A true, hidden lunar basin or just a neat coincidence between a lot of ancient, mostly collapsed crater rims? But if the latter, why is the albedo lower inside it in such a nice, circular shape that follows the outline perfectly? 

 

Why have I never heard of this before? 

 

 

Clear skies!
Thomas, Denmark

WOW! Nice!


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#15 AllanDystrup

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Posted 29 November 2019 - 04:37 AM

.

Lunar Basins...

    

    

     I stumbled upon this overview of Lunar basins in another context, and thought I'd share it here;

 

     The overview includes 43 large impact basins on the Moon as identified by Spudis (1993/94) and Wilhelms (1987). The pre-Nectarian ones are of course those hardest to identify. I miss the pre-Nec Procellarum (Gargantuum) basin in the overview though...

    

Lunar Basins 01.png
Lunar Basins 02.jpg

*click*

    

     -- Allan


Edited by AllanDystrup, 29 November 2019 - 04:46 AM.

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