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Another month, another sunset on the waning Moon, October 20, 2019

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#1 Tom Glenn

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Posted 22 October 2019 - 03:08 AM

This image was taken at dawn on October 20, 2019, at 13:21UT.  I almost didn't bother waking up to image, because the seeing forecast was only "average", which is never a good sign as these predictions are usually extremely optimistic anyway, and the atmosphere seemed unstable when I went outside, with stars flickering everywhere despite the clear sky.  However, the waning Moon near Last Quarter is very high in the autumn sky, and on this occasion the Moon was at 80 degrees elevation, so despite being tired I decided to give it a go.  This is a small sample of data, which corresponds to the same region that I posted from last month.  This image, however, is taken with the sunset terminator about 13 hours away from the position in the last image.  Below is the image, presented at 67% of the original scale.  I am also posting a comparison between the two images, so you can see the movement of the terminator during this time interval.  The recent image had to be slightly rotated and cropped in order to present the two images at the same scale, because the libration angles were different.  There is about 3 degrees of libration in latitude difference between the two images, which corresponds to roughly the diameter of Tycho, and so this causes an apparent rotation of these features towards the South Pole of the Moon.  You can clearly see this if you try to match landmarks.  There is also about a 1 degree difference in libration in longitude, but this is less apparent.  

 

Once again, the image was taken with the C9.25 Edge HD and ASI183mm with 500-575nm filter.  Stack of 500 out of 5000 frames.  Despite downsizing the image to 67%, there is still good detail visible, and the downsizing allows me to put more of the original image into the field of view.  You will need to click for larger size!

 

Moon_102019_1321UT_TG.jpg


Edited by Tom Glenn, 22 October 2019 - 03:13 AM.

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#2 Tom Glenn

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Posted 22 October 2019 - 03:10 AM

Comparison of two images of the same region of the Moon, separated by about 13 hours of movement of the terminator.  Image on the left is from October 20, 2019, and on the right is September 21, 2019.  Click for larger size!

 

terminator_comparison.jpg


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#3 Foc

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Posted 22 October 2019 - 04:27 AM

Very attractive images as well as the interest in the combination illustrating the apparent rotation due to libration.


Edited by Foc, 22 October 2019 - 04:27 AM.


#4 kbev

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Posted 22 October 2019 - 09:04 AM

Nice image Tom! Looks like we were out at roughly the same time Sunday morning. One of the things I noticed when I was imaging this area was the central peak of Moretus catching the last of the sunlight as the terminator sweeps west.

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#5 Tom Glenn

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Posted 22 October 2019 - 09:13 PM

Thanks for the comments Foc and Kevin.  Kevin, Moretus is a very striking crater that provides a very nice oblique perspective, and it has an impressive central peak.  I'm reminded of a post I made last year of the same region, with nearly the same lighting as this image, in which I commented on the "sundial" effect that the central peak of Moretus was making.  The same effect is taking place in the current image.  Note that in last year's image, Moretus is even closer to the limb, as libration in latitude was near maximum.  

 

https://www.cloudyni...tor-aug-3-2018/


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#6 Kokatha man

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Posted 23 October 2019 - 06:28 PM

A nice terminator image as well as libration comparison Tom waytogo.gif waytogo.gif ...& 80° elevation for the Moon - that's Jovian heights down here recently..! :lol:



#7 Tom Glenn

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Posted 29 October 2019 - 11:18 AM

Thanks for the comments Darryl, and to all for the additional likes.  80 degree elevations are indeed nice to work with, although not by any means a guarantee of success.  Most planets will remain low here for a while, although Mars will get to over 60 degrees next year, which is very nice!



#8 kevinbreen

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Posted 04 November 2019 - 02:04 PM

This image was taken at dawn on October 20, 2019, at 13:21UT.  I almost didn't bother waking up to image, because the seeing forecast was only "average", which is never a good sign as these predictions are usually extremely optimistic anyway, and the atmosphere seemed unstable when I went outside, with stars flickering everywhere despite the clear sky.  However, the waning Moon near Last Quarter is very high in the autumn sky, and on this occasion the Moon was at 80 degrees elevation, so despite being tired I decided to give it a go.  This is a small sample of data, which corresponds to the same region that I posted from last month.  This image, however, is taken with the sunset terminator about 13 hours away from the position in the last image.  Below is the image, presented at 67% of the original scale.  I am also posting a comparison between the two images, so you can see the movement of the terminator during this time interval.  The recent image had to be slightly rotated and cropped in order to present the two images at the same scale, because the libration angles were different.  There is about 3 degrees of libration in latitude difference between the two images, which corresponds to roughly the diameter of Tycho, and so this causes an apparent rotation of these features towards the South Pole of the Moon.  You can clearly see this if you try to match landmarks.  There is also about a 1 degree difference in libration in longitude, but this is less apparent.  

 

Once again, the image was taken with the C9.25 Edge HD and ASI183mm with 500-575nm filter.  Stack of 500 out of 5000 frames.  Despite downsizing the image to 67%, there is still good detail visible, and the downsizing allows me to put more of the original image into the field of view.  You will need to click for larger size!

 

attachicon.gif Moon_102019_1321UT_TG.jpg

 

This is one of the best moon images I have ever seen. Fantastic.




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