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The Classic Moon

beginner classic moon refractor
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#201 AllanDystrup

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Posted 31 March 2021 - 02:25 AM

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6-Day Moon
Crop: Janssen

     

     

    Janssen is a large, old crater (Pre-Nectarian, ~4.3 Byr), with a floor covered in Nectarian ejecta (3.9 Byr); The floor shows an interesting highland rille system (Rimae Janssen), where the N rille is broad and looks like a tension crack in the fluidized Nectaris ejecta, while the W rille is narrower and looks a bit like the Hyginus rille, composed of several small volcanic pits.

     

     Young Fabricius (Eratosthenian, ~2 Byr) has impacted on the NE crater floor of Janssen, where part of its NE crater rim pushed up against the Janssen crater wall, where after it slid down like a horse-shoe shaped terrace around the central mountain.

     

2021-03-31 8-Day Moon - Janssen.jpg

*click*

     -- Allan

     

 


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#202 AllanDystrup

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Posted 06 April 2021 - 01:15 AM

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8-Day Moon
Overview

     

     

     It’s the end of March and I’m out in the evening to study the 8-Day Moon (2021-03-21 @  22:00 Local CEST, UT+1). The waxing half Moon is well up at 41° altitude above the W horizon, the weather is cool and calm, and both transparency and seeing are well above medium. All-in-all a splendid evening, so I plug in a 500nm Green Bandpass filter on my Zeiss 100/640mm refractor, and off we go for a sweep down the lunar terminator.

     

     I first take in the full-frame view of the half moon, -- crisp and clear and ready to go for higher resolution tonight! Many interesting areas to study (Alpine Valley and Cassini, Apennine Bench and Mountains, the Hyginus-Triesnecker rille area, the Ptolemaeus-Alphonsus-Arzachel craters...), but I decide to concentrate on the Southern Highlands, from Deslandres down to the South Pole.

     

8-Day Waxing half Moon.png
Full Res & Zoom-in: https://www.flickr.c...tetaken-public/

     

     Ahh well, -- sweeping across one of my favorite lunar landscapes (the ABF), I decide to spend some time enjoying this geologically interesting formation too, so I may as well share this observation here also...

     

     -- Allan


Edited by AllanDystrup, 06 April 2021 - 08:37 AM.

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#203 AllanDystrup

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Posted 07 April 2021 - 02:12 AM

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8-Day Moon
Crop: Apennine Bench

     

     

     ABF (the Apennine Bench Formation) consists of several light-hued, hummocky plains found mostly between the second ring (Archimedes/Wrinkle Ridge) and the third ring (Apennine/Basin Rim) of the Imbrium basin; -- The ABF includes terra-formations that are topographically higher than the mares but lower than the highlands.

     

     The ABF was formed on the Imbrium basin floor shortly after the Imbrium impact (period Lover Imbrium: 3.84 Byr) by KREEP-rich magma erupting from the upper lunar mantle through deep cracks in the thin crust, which was already shattered by the Procellarum basin impact. The large, early Imbrian crater Archimedes impacted directly on top of the ABF-plains, (around ~3.7 Byr ago) next to a part of the Imbrium basin rim (the Apennine Mts.) that has slid down as slump terrasses (now known as the Archimedes Mts.)

     

     Later (in Upper Imbrium: 3.6-3.2 Byr) massive, low viscosity basaltic lava floodings filled the Imbrium basin to about half its original depth, thus creating Mare Imbrium (and also flooding the other major impact basins on 30% of the lunar near-side). The Imbrian lava flooding embayed the Archimedes Mts. and crater, seeped up through cracks in the Archimedes crater floor and covered part of the ABF east of Archimedes (now known as Palus Putredinis).

     

     Later still, other large impacts occurred on the ABF, each throwing out ejecta carpets covering the surroundings; Most notable examples are Autolycus (Eratosthenian: 2.1 Byr) and the more recent Aristillus (Copernican: 1.3 Byr), still with obvious radiating ridges.

     

     

2021-03-21 8-Day Moon - ABF01.jpg

2021-03-21 8-Day Moon - ABF02.jpg

*click*

Illustration from Paul Spudis: Composition & origin of the ABF
Proc. Lunar Planet Sci. Conf. 9th 1978, USA.

 

     

     -- Allan


Edited by AllanDystrup, 07 April 2021 - 02:40 AM.

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#204 jimsmith

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Posted 07 April 2021 - 05:58 AM

Thank you, Allan. This is fascinating stuff. Can I ask, what is the purpose of the green bandpass filter?

 

Thanks, Jim



#205 AllanDystrup

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Posted 08 April 2021 - 02:51 AM

Hi Jim,

     

     I seldom use any filters for visual observation of the solar system with my APOs; With achromats I have obtained increased contrast using a light-blue or green (540nm) on the sun and a yellow (495nm) on the moon; Even a semi-APO like my Zeiss AS 80/840 benefited from the yellow filter. These color bandpass filters work by reducing the effect of chromatic aberration.

     

     For photography there are several factors in play:

  • angular resolution (AR): imaging in shorter wavelengths (green bandpass with UV/IR block) increases the AR;
    Blue light is scattered more by the atmosphere, which decreases the AR here on the surface of the Earth (maybe better on Mars?)
     
  • atmospheric turbulence (AT): imaging in longer wavelengths (red into IR) is less affected by adverse seeing and transparency; The larger the aperture (above say 4”) the more negative effect of AT.

     I currently image with a monochrome sensor (IMX183mm) at prime focus on my preferred small(ish) 4” f/6.4 APO; I observe from my suburban backyard in a temperate costal climate N of Copenhagen (Denmark), where my seeing and transparency are mostly around medium, often below that and seldom good to excellent. I don’t bother imaging in well below medium seeing (high AT and/or low transparency).
     

     I use a red (610nm longpass) filter for dusk/dawn or daytime lunar imaging, -- not so much to reduce the effect of AT (my preferred aperture being only 4”), but primarily to increase contrast. My 180 f/10 Mak was more sensitive to AT and thus less time diffraction limited, so I did more often use a red filter on that scope.
     

     I use a green (610nm bandpass) on my 4" refractor in medium to excellent seeing with good results for increased AR.
     

     -- Allan


Edited by AllanDystrup, 08 April 2021 - 07:39 AM.

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#206 jimsmith

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Posted 08 April 2021 - 08:19 AM

Thanks for the comprehensive explanation.

 

I have taken one or two lunar photographs but I would like to do some more. I have a 4" SkyMax Maksutov, a 2.5x Powermate and two cameras to try...a Nikon D5500, and with smaller pixels, an Altair GPCAM3 178C. I shall try out various combinations at the next opportunity.

 

Have you found a reliable source for predicting seeing and transparency conditions?

 

Regards, Jim



#207 AllanDystrup

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Posted 11 April 2021 - 04:12 AM

Have you found a reliable source for predicting seeing and transparency conditions?

     Well, there are several weather web-sites and apps that have information on local seeing and transparency, -- but what is the most reliable for you depends on your location. Some I'm currently using (for Scandinavia) are: "Meteoblue.com" and the apps "Xasteria", "Sat24" and "Weatherology". The most reliable source for info on seeing and transparency however is just poking your head out the door, and if that looks good, have a quick look at the moon and/or a startest. This will tell you all you need to know. grin.gif 

 

 

8-Day Moon
Crop: Deslandres

     

     

    The Southern Cratered Highlands have seen no major Imbrium mare-lava floodings, but are dominated by ancient impacts in the lunar terra crust. Some of the largest impacts in this area are the old Pre-Nectarian basin structures: Werner-Airy (VA: 500km ø) and Mutus-Vlacq (MV: 700km ø), but the large walled "Hell Plain" Deslandres (235km ø) can also be considered a smaller basin impact with a possible 70km ø inner ring.

     

     The Nubium Basin bordering on the Highlands towards NW is also Pre-Nectarian (but older than Deslandres), and it was mare-filled in the great Upper Imbrian lava flows; The Highlands though, including the ancient basins VA and MV, were not flooded by the Imbrian basaltic lavas, but instead repeatedly molded and battered by impact cratering; This long-lasting bombardment has resulted in a zone of ancient fractured megaregolith (brecciation) down to on average 2km depth, overlaid by a ~10m layer of smoother regolith plains material from the cratering ejecta consisting of impact melt and pulverized crust.

     

     As an example, the floor of Deslandres is rough, pockmarked by several medium-size primary craters: Lexell, Walter W, Hell ("ghost", A, B, C) and on top of that, pitted by countless smaller secondary craters, some in chains (catenae) and clusters, like the one that includes Cassini's "bright spot". Also note the 110km long (unnamed) trough (valley) running diagonally from NW towards NE, -- radially to Imbrium, which may indicate the origin of this formation.

     

     A couple of patches towards the NE on the Deslandres crater floor are smoother and darker than the rest, maybe caused by non-mare volcanism. Some surrounding craters - including Regiomontanus, Walter and Stöfler - have larger areas with smooth (young) floors, possibly formed by dark non-mare volcanism and later streaked with light hued impact ejecta (?).

     

8-Day Moon - Deslandres 02.png
*click*

     -- Allan


Edited by AllanDystrup, 11 April 2021 - 05:56 AM.

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#208 AllanDystrup

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Posted 26 April 2021 - 03:03 AM

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11-Day Moon

     

     

     The gigantic Procellarum impact basin formed ~4.3 Gyr ago (Pre-Nectarian) in the residual melt from the ancient Lunar Magma Ocean; This melt is characterized by a high content of Potassium/Kalium, Rare Earth Elements and Phosphorus (“KREEP”). Later, ~3.9 Gyr ago, the smaller lunar basins formed during the heavy bombardment, and in the following 3.8-3.2 Gyr (Late-Imbrian) period the basins were filled with low-Titanium lava flows from the then still partially melted lunar mantle.

     

     Imbrium is the largest of the well-preserved lunar basins, and it was formed on the Procellarum KREEP-rich terrane, parts of which was excavated and deposited in the basin rim ejecta (as sampled on the Apennine Bench by Apollo 15 at the Hadley Rille). Three later lava flows with increasing levels of Titanium have occurred on top of the thick early Imbrium lava cover, -- all originating from volcanic shield eruptions in a small area SW of the crater Euler and from here flowing up NE towards the Helicon crater :

     
  I: Late Imbrian flow (3.0 Gyr) up to 10m thick and extending 1200 km
 II: Early Eratosthenian flow (2.7 Gyr) 15-25m thick and extending 600 km
III: Middle Eratosthenian flow (2.5 Gyr) 25-60m thick and extending 400 km

     

     The  source region for these (relatively) young lava sheets is located where the second Imbrium basin ring crosses a fraction line around the Copernicus crater, possibly providing crust fissures/conduits for low-viscosity and fast extrusion-rate lava flows, which can still be identified as cones/vents (Mt. Vinogradov), channels (Rima Euler), levees and flow fronts (for the II and III lava fields, eg. around Mt. La Hire).

   

     

     Below is shown the 11-day waxing gibbous moon with Mare Imbrium framed. In the following image is shown a zoom-in/crop of the Mare Imbrium region, and the next image is annotated with the young phase I-II-II lava flows emanating from the Euler fracture region and extending up NE past Mt. La Hire towards the Helicon crater.

 

11-Day Moon 2021-04-22 Full Frame.jpg

11-Day Moon, 4” f/6.4 prime focus full disc and full resolution:

https://www.flickr.c...tetaken-public/

 

11-Day Moon 2021-04-22 Imbrium.jpg

11-Day Moon 2021-04-22 Imbrium Annotated.jpg
*click*

     

     The Moon was well up above the horizon (40° Alt.) and both seeing and transparency were around medium. The time was late afternoon bordering on civil dusk ('golden hour') with a still blue daylight sky, so I used a green longpass filter for better contrast. The result is only “so-so” for finer details, but I’m having a busy spring with garden, building and family projects, so I have to work with what opportunities I get for astronomy.

     

     -- Allan

 


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#209 AllanDystrup

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Posted 27 April 2021 - 07:39 AM

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Euler and Mt. La Hire volcanic features

     

     

     The mountainous area SW of Euler (‘Natasha Hills’) may be the remains of a slump terrasse that slid down during a collapse of the Imbrium basin rim (i.e. from the Carpathian Mts., -- much like the Archimedes Mts. Slide at the Apennine Bench); More recent topographic investigations (LRO, Kaguya, Clementine) have revealed that the young Mare Imbrium lava flows show well defined flow margins, levees and channels that are traceable back to a source region SW of Euler crater. 

     

     Around Mt. La Hire the phase II and III lava flows converge, showing sheets with lobate margins and channels surrounded by levees. These morphologies cannot be clearly seen on my zoomed-in image crop below, -- the resolution is simply not high enough due to my limited (4”) aperture and the mediocre seeing this afternoon. I have however included a LROC:QuickMap transect from the area just SE of Mt. La Hire, displaying a cross section of several lava channels with surrounding levees.
       
     The region SW of Euler shows several features of volcanic origin: domes with central pits, lava channels (rimae) and lava tubes with collapsed roofs. I’ve marked a couple of domes plus the position of the Euler rilles on my image below. These were all hard to spot during my observation, but I’ll try again under better observing conditions. I include a 3D view of the dome with central pit, which I’ve indicated as #1 on my image. This view (3x height exaggerated) was created using the LROC:QuickMap application.

     

Euler Region.jpg

*click*

     -- Allan


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#210 AllanDystrup

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Posted Yesterday, 06:24 AM

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11-Day Moon
Copernicus South

     

     

          Insularum is the common name for the lava-covered trench bordering the Imbrium Basin rim (3.8 Gyr) towards the south, i.e.  S of the Carpathian and Apennine mountain ranges. The Insularum mare lavas (age ~3.6 Gyr) were partly covered by dark mantle deposits (DMD): fine volcanic ash from explosive “fire fountain” eruptions, stretching from the E shores of Sinus Aestuum across eastern Mare Insularum.

     

11DY Moon - Copernicus area.jpg
*click*

 

     Later, a large young impact (<1.1 Gyr) created the magnificent 93 km wide Copernicus crater on top of the dark lava and ash deposits, complete with central crater peaks, a 1 km high rim surrounded by a large ejecta carpet with chains of secondary craters and a light hued web of ejecta rays. The young small crater ‘Copernicus H’ has dug through the ejecta carpet S of Copernicus, down to the underlying DMD-layer, leaving a dark halo around the crater.

     

11DY Moon - Copernicus S.jpg
*click*

     -- Allan


Edited by AllanDystrup, Yesterday, 06:25 AM.

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#211 AllanDystrup

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Posted Today, 01:15 AM

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11-Day Moon -- Crop
Mare Insularum South
Apollo Missions

     

     

     After the Apollo 11 mission to the eastern old Mare Tranquilitatis,  the following two successful Apollo missions (12 and 14) were designated to explore the younger mare region (12) and an ejecta blanket  (14), both in the central equatorial region of the Moon. 

     

     Apollo 12 touched down 370 Km S of Copernicus on a bright ejecta ray from the young Copernicus impact; The samples collected from this site showed that the dark mare basalts in S Insularum were 500 Myr younger than Mare Tranquilitatis and that the ejecta ray material could date the Copernicus impact to only ~850 Myr ago.

     

     Apollo 14 landed 500 Km S of the Imbrium Basin rim (Mts. Apenninus) on a rough ejecta carpet from this impact containing smoother patches, which were thought could be of volcanic origin; Analysis of the collected samples from the blanket of debris however, showed no volcanic basalts, but rather complex breccias, including some excavated pre-Imbrium (3.9 Gyr) rocks and some conglomerates containing melt from the Imbrium impact (3.8 Gyr).

     

Insularum S -- Apollo.jpg
*click*

     -- Allan

 

 

     

 

 


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