11 replies to this topic

[PKDfan]

A closeup


This mountain unbelievably was moved back out of sight within a few minutes of taking the image.
Taken april 21 1:59am 2024

THANKS for any help you might have.


Clear Steady Skies
Lance
Edit this daylight saving Mountain time

Edited by PKDfan, 17 February 2025 - 12:44 AM.

[NiteGuy]

It may not be a mountain at all.

 

Possibly an impact plume from a small meteor.

[scottinash]

Possibly the eastern side of Harlan crater rim toward Gum S and Gum?

Edited by scottinash, 17 February 2025 - 09:10 AM.

[PKDfan]

It may not be a mountain at all.

Possibly an impact plume from a small meteor.

I wish it was ! How cool would that be !!

CSS
Lance

[PKDfan]

Possibly the eastern side of Harlan crater rim toward Gum S and Gum?

Thanks scottinash !

I think it might be a rim peak off Oken south flank but your idea works too ! Harlan has a west flank peak too.

I Really need a better moon map.


Thanks for the help !!


CSS
Lance

[Tom Glenn]

The NASA Dial-A-Moon website is an excellent first stop to obtain a simulated view of the Moon at a specific time.  In this case, I think the feature you are seeing in your image is an artifact, likely from unstable seeing.  What appears as a mountain peak in your image does not correspond to any feature shown in the simulated images (reproduced below).  At the time of your image, the limb near Mare Australe is very smooth, with no prominent peaks at the location indicated in your image.  You also mention that the peak disappeared after just a few minutes.  Peaks along the sunlit limb of the Moon only appear to move with changes in libration, and would show no change over the course of minutes.  A noticeable change in libration would likely require at least a day to notice, even with high resolution imaging.  

 

[scottinash]

As usual, you present a lot of good info, Tom.     When I first saw Lance's post, I pulled up an image of this region taken by Physicsman last year, which we worked on jointly to label.  Note that this image was taken at a different time (I think around May 2024) so it doesn't match Lance's image libration perspective exactly.  My intention is to show that there are several slightly elevated features along the limb.  

 

Side note: I find that most "soft tools" seem to flatten the limb horizons.  I do enjoy using ACT Quickmap (Lunar Globe 3D option) to study various limb angles/perspectives - you can use your keyboard arrows and/or mouse to travel/orbit the area from different perspectives/viewpoints.

 

 

 

Edited by scottinash, 18 February 2025 - 12:51 PM.

[PKDfan]

The NASA Dial-A-Moon website is an excellent first stop to obtain a simulated view of the Moon at a specific time.  In this case, I think the feature you are seeing in your image is an artifact, likely from unstable seeing.  What appears as a mountain peak in your image does not correspond to any feature shown in the simulated images (reproduced below).  At the time of your image, the limb near Mare Australe is very smooth, with no prominent peaks at the location indicated in your image.  You also mention that the peak disappeared after just a few minutes.  Peaks along the sunlit limb of the Moon only appear to move with changes in libration, and would show no change over the course of minutes.  A noticeable change in libration would likely require at least a day to notice, even with high resolution imaging.  

 

Dial_a_Moon-1.jpg

Dial_a_Moon_2.jpg

 

I'm sorry Tom but that libration timeframe is wildly out whack.

 

I spent four hours observing the south pole on april 20 & 21st/2024 and in that short period the moon nodded in and out so quickly that if you weren't watching continuously you'd have missed the Leibonitz mtn and several south pole peaks.

 

Thanks for the link though !

 

I believe that this is not an artifact and in my high resolution map Oken and a crater between Gum s and Abel b have mtns on their rim edges and is not so flat.

 

 

 

First is Oken area & second Gum & Abel area.

 

 

CSS

Lance

[Tom Glenn]

Lance, I appreciate the discussion.  Please see below. 

 

I'm sorry Tom but that libration timeframe is wildly out whack.

 

I spent four hours observing the south pole on april 20 & 21st/2024 and in that short period the moon nodded in and out so quickly that if you weren't watching continuously you'd have missed the Leibonitz mtn and several south pole peaks.

 

The very rapid changes you are describing are caused by changes in solar illumination, not libration.  Sorry if my statement in the previous post was unclear.  I was referring to changes in perspective of features on the sunlit limb, not to changes in illumination near the terminator (because your feature in question is not near the terminator).  Illumination changes can indeed be very dramatic and rapid near the terminator as the sunlight and shadows move quickly.  Libration, on the other hand, is the wobbling of the Moon due to parallax, or the apparent shift in an object that occurs when changing viewing angles.  This is caused by the movement of the Moon relative to the Earth.  Changes in libration are much slower to be perceived than changes in illumination.  In fact, we can look up the exact values at any given time.  Libration is typically reported by providing the coordinates of the sub-Earth point, and at the time of your image, the sub-Earth point was located at -1.564 S, -0.596 W (values in degrees).  Four hours later, the sub-Earth point was -1.333 S, -0.821 W.  This is a very small change that would not be perceived at the image scales you are sharing with us.  

 

I believe that this is not an artifact and in my high resolution map Oken and a crater between Gum s and Abel b have mtns on their rim edges and is not so flat.

 

Your hypotheses are very reasonable.  The way to test them is to determine if such craters do in fact project above the limb at the time of your image.  The NASA Dial-A-Moon images I posted yesterday indicate that they do not.  But if you don't like that reference, we can also look to LTVT (more on that below) to produce a simulated image at the same time.  This is reproduced below, with a few landmark craters labeled.  The image indicates a relatively smooth lunar limb, with some very slight irregularities, but nothing that corresponds to the peak shown in your image.  Some of the difficulty is due to the limitations of resolution in your image. 

 

 

The gold standard for identifying features along the lunar limb is to use software that simulates the view from Earth and provides a mechanism to take accurate latitude and longitude measurements that may be cross referenced with LROC data.  The best example of such software is LTVT, although the software does require considerable practice in order to use effectively.  As it turns out, I'm very familiar with the Mare Australe region, having done an analysis several years ago posted here, as well as in an image I captured of the region during an occultation of Mars.  All the crater identifications were performed by matching precise locations in the images to latitude and longitude coordinates (with the help of LTVT) that could then be looked up using the LRO Quickmap for verification.  Peaks are sometimes visible along the limb in this region, although they tend to be very subtle ones, and conclusive identification is not always easy without some of the methods mentioned above.

Edited by Tom Glenn, 19 February 2025 - 05:03 AM.

[Claude Navarro]

Lance,

It's not a mountain, just a slope revealing either a steep crater rim or a peak within a crater. For example, if you look closely at my image, you can see on the limb something similar to what you've noticed.

Claude N.

 

[Tom Glenn]

I don't think it's possible to say what it may correspond to though in this case, Claude.  I reproduced the OPs image at 200% scale.

 

 

Could it be something like what Claude showed in his image?  Maybe, but honestly the resolution of this image is quite limited, and the limb is saturated.  There are no obvious candidates in the simulated image along the limb at this time.  It might be helpful to know more about how this image was processed, and if perhaps a more "raw" version could be provided.  It's possible that a very small irregularity in the limb has become exaggerated during processing. 

[PKDfan]

Thanks very much Tom and Claude for your help!!

Its really appreciated.

Obviously i need to be more diligent and keep an eye open for this limb mystery on other months with similiar librations.

I love that the moon has so many surprises left to discover.


Lets keep the lunar love alive !


CSS
Lance