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Arzachel with the C8

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#1 GEC

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Posted 02 August 2021 - 10:12 PM

After Jupiter I had a quick go at the Moon on July 31st.  Arzachel with its rimae and the smaller crater Alpetragius to the left.  Prime focus with the NexImage 5 camera.  I wish I had continued with Alphonsus as well. The braided looking terrain in that crater is interesting.

 

 

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  • 2021-07-31-0925_5_Arzachel_C8_F12_Nl5.jpeg

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#2 Jim Waters

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Posted 02 August 2021 - 11:06 PM

Nice image GEC.  How many stacked and processed images is this?



#3 spereira

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Posted 03 August 2021 - 07:29 AM

Moving to Lunar Observing & Imaging.

 

smp


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#4 GEC

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Posted 03 August 2021 - 04:55 PM

Thanks Jim,

 

NexImage 5 camera

12,681 frames captured in Sharpcap

    Gain was set to 33 (33 percent?)

     Exposure was .056 s which would be anout 18 frames per sec

 

50% stacked in Autostakkert 3

wavelets in Registax 6

processed and cropped in Gimp

 

Not too much processing done.



#5 Tom Barnacle

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Posted 04 August 2021 - 02:25 AM

Fantastic image!

 

That braided terrain is a ridge of ejecta from Arzachel that bisects the floor of Alphonsus - it is often said to be part of the Imbrium Sculpture but is not.  If you look closely at the left hand side of the ridge in your image you can see that there is a line of elongate secondary craters just peeping out from beneath it - these craters formed first during the Arzachel impact event. The ridge then formed as a result of, I suspect, collimated plumes of debris that was ejected from the crater northwards, and were deposited over the surface, including the secondary craters that formed earlier. The ridge has a herringbone pattern typical of interfering ejecta deposits - you can see this in you image. The reason this ridge is here is that Arzachel is a low angle impact crater, with the impactor having arrived from the south - not low enough to produce an elliptical crater, but low enough to influence the ejecta pattern.

 

You can see something similar if you look at Cardanus - also a low angle impact from the south (but not as low as Arazachel probably). Here two converging crater chains (one being Rima Cardanus) stretch away from Cardanus and across the floor of Krafft, where they converge on the northern rim. The crater chains are then overlaid by later ejecta that drapes the surface and partially obscures the chains. Same process as seen in Arzachel.

 

The ridge across Alphonsus divided that crater into two, the eastern half then filled with volcanic deposits of some form, but the ridge prevented the spread of these deposits across the western half - thats why in low angle images the two halves of Alphonsus look so different, with the western floor looking more heavily cratered and older.



#6 GEC

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Posted 04 August 2021 - 04:00 PM

Thank you Tom.  One of the nice things about this site is that knowledgable members are willing to share.  Learning something of the history of these formations makes observing them more meaningfull. 


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#7 Tim J Fowler

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Posted 06 August 2021 - 07:33 PM

Thank you Tom.  One of the nice things about this site is that knowledgable members are willing to share.  Learning something of the history of these formations makes observing them more meaningfull. 

Astrophotography is a lot like golf. You start out bad, and have plenty folks telling you how to get better. At least most of the folks here are better than a 20 handicap!




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