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Stub Mandrel

Exploring the Sea of Tranquillity at High Resolution

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The Southern Half of Mare Tranquilitatus (The Sea of Tranquillity)

Well known as the location of the first Moon landing by Apollo 11, this area was well explored before the landings by robotic probes. The landing site was chosen because of its relatively flat terrain, rather than for interesting geology, however, as this image shows the wider area contains many interesting features (the labelled image is not an entry, but is to assist with identifying the key features).




Arago Domes

These two rounded domes to the north (α) and west (β) of the crater Arago are a pair of shield volcanoes formed of thick, sluggish lava. Only a few hundred metres height they are only clearly observed or imaged when the light is low.

Aridaeus Rille

The double crater Aridaeus lies at the eastern end of a 300 kilometre rille. It is considered to be a ‘graben’ -  a block of the crust which has sunk down between two parallel faults.


This carter is noted for its bright rim and dark rays, however, these are barely visible in this image as, like most crater rays, they appear strongest when the sun is overhead.

Sabine and Ritter

These two craters, are near-twins in size and with respect to the concentric features inside them. For many years they were thought to be volcanic calderas, but they have since been determined to be impact craters.


This small crater has a sharply defined rim and is surrounded by bright material.

Hypatia Rilles

The Hypatia Rilles are a system of graben on the south-west margin of Mare Tranquillatatis. There near-alignment with Sabine and Ritter was once thought to be evidence of the craters having a volcanic origin.

Delambre Crater

The terraced inner rim of this crfater is hidden in shadow, but you can see the tiny craterlet on its northern rim. The two craters to its west are the unconventionally named Theon Junior and Senior.


This curiously irregular crater has an undulating central plain, with a low peak in the centre.


This small crater is 6km in diameter. It has a dark central spot which is about 1,000m across, which appears to have been resolved.


Censorinus would be one of the less significant landmark, if it wasn’t for the presence of short, bright rays radiating from it, which make it one of the brightest points on the Moon’s disc.


This 12km crater is intersected by s curved ridge running approximately north south. It is unusual in being named after a Greek benefactor of astronomers, rather than an astronomer or philosopher.


The low angle of illumination of this image reveals the huge-double walled ‘ghost crater’ Lamont which appears to have been submerged by the lavas which fill Mare Tranquilitatus.

Ranger 8

Ranger 8 was a 1965 lunar mission, one of a series of survey spacecraft that obtained close up images of the moon. It returned over 7,000 images before crashing into the surface and creating a 13.5 metre crater, which is to small to show in this image.

Surveyor 5 Landing Site

This lander one of the successful lander missions to the moon that paved the way for Apollo. It successfully operated from September to December 1967.

Apollo 11 Landing Site

Perhaps one of the most significant archaeological sites in the solar system, ‘Tranquillity Base’ is the place where human beings first stepped onto the surface of another world in 1969.

Aldrin, Collins and Armstrong

These three modest craters record the names of the three astronauts who participated in the Apollo 11 mission.

Image Details

This image was taken using a Skywatcher 150PL reflector on an EQ3 mount, using an x3 barlow for an effective focal length of 3.6 metres. Using a Touptek mono camera this gave 0.25 arc minutes per pixel, which is slightly oversampling, but an x2 barlow would probably under-sample with this scope. Exposure was limited to 25ms to minimise the effects of slightly better than average seeing.

The theoretical resolution for a 150mm telescope is about 0.75 arc seconds. At the distance of the moon, this corresponds to 1,500 metres – just under a mile but is not uncommon for stacked lunar and planetary images under good conditions to exceed this limit.

Collins crater is 2.4 km across and has resolved as circular with a shadow crossing its bowl, indicating that the imaging scale was well matched to the setup.

Edited by Stub Mandrel
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