Walking the Moon with my own Photos - Overview

Overview of my Moon Walks | Information about the Moon | Elements of the Moon Surface | How Small Objects Can You Still Recognize? | Software | References

On these pages I "walk the moon" on the basis of my own photos. In other words, I try to name the objects on my lunar photos to get to know the moon better. Maybe these pages will help others to get to know the moon better as well...

On this page, I provide an overview of the "moon walks" and some information about the moon.

 

Overview my Moon Walks

 

Information about the Moon

Latin and English Names of Seas/Oceans

Mare Cogitum Sea of Knowledge
Mare Crisium Sea of Dangers
Mare Fecunditatis Sea of Fertility
Mare Frigoris Sea of Cold
Mare Humorum Sea of Moisture
Mare Imbrium Sea of Rain
Mare Nectaris Sea of Nectar
Mare Serenitatis Sea of Cheerfulness
Mare Tranquilitatis Sea of Calm
Mare Vaporum Sea of Vapors
Oceanus Procellarum Ocean of Storms

Numbers

Mean distance from the earth 384,400 km
Closet distance 356,000 km
Farthest distance 407,000 km
Diameter 3,476 km
Circumference 10,920 km
Mass 1/81 earth masses
Specific weight 3.3 g/ccm
Sidereal orbit period (star - star) 27.32 days
Synodic orbit period (New Moon - New Moon) 29.53 days
Smallest angular diameter 29' 26"
Largest angular diameter 33' 30"
Overseeable area (thanks to the libration) 59%

 

Elements of the Moon Surface

Elements of the Moon Surface - in Brief

Elements of the Moon Surface - Short Version (According to Spix moonscout, Adapted)

Elements of the Moon Surface - Long Version (After Spix, Adapted)

Seas and Highlands

Seas (lat. Mare) are largely flat, often circular basins and irregular depressions, which very created by the impact of very large celestial bodies that hit the lunar crust and which were later flooded with dark lava.

Highlands (lat. Terra) are the bright areas of the moon's surface. They used to be considered continents. They are structured like mountains, dotted with countless craters and traversed by valleys, making them the most richly structured lunar surfaces.

Craters, Ring Mountains and Wall Plains

Craters are the most common lunar formations and are usually also caused by meteorite impacts. They are roughly divided into the following classes:

Mountains and Valleys

The "real" mountains (lat. Montes) of the moon usually run along the edges of the moon seas. They are mighty crater walls which were formed during the formation of the moon seas and later partly flooded with lava. They reach heights of up to several thousand meters. In the telescope, the mountains look very rugged due to the shadow cast. In fact, however, they are more comparable to huge hills.

Single standing mountains (lat. Mons) are to be found practically only in the moon seas. These mountains are also peaks of crater walls rising from the lava-covered plains.

Valleys (lat. Vallis) are divided into three types according to their different history:

Grooves and Furrows

Due to their different origin, grooves (lat. Rima) are divided into different types:

The term furrow (lat. Rupes) is equated with a whole series of terms: steep slope, mountain slope, or cliff.
Essentially, two types are to be distinguished:

 

How Small Objects Can You Still Recognize?

When you take photos of the moon, of course, the question arises how small objects you can see or recognize on photos. Since I do not take enough time with visual observations and do not inform myself properly beforehand, the question remains, what can be seen on the photos. A quick empirical answer is that, in my photos, you can see minimum objects with a diameter of 10 to 20 km. The image resolution seems to depend less on the magnification (also through the camera optics), but rather on the telescope itself, i. e. its aperture. Since the aperture determines the resolution of telescopes, my first impression is no surprise.

In the following, I will extend the question to the eye, visual observation with the telescope, the Atik Infinity camera at the telescope, and a camera at the telescope using the 1:50 or projection method.

What Does the Naked Eye See on the Moon?

With a lunar diameter of 3,476 km and a field of view of approx. 30' (0.5°) = 1800", an arc second would result in a distance of approx. 2 km (1.93 km).

The theoretical resolution of the eye is given as 20", which corresponds to 38.6 km. In practice, however, only 60" = 1' are achieved, which corresponds to 115.87 km. This means that the smallest moon structures that can be seen with the naked eye are about 120 km in size (116 km exactly). This corresponds to the crater Alphonsus (118 km diameter).

What Do I See with my Telescopes on the Moon?

Now I will calculate the theoretical resolution of my telescopes! We already know that an arc second corresponds to a distance of about 2 km (1.93 km). Depending on the aperture, my telescopes have a theoretical resolution between 1.15" (4" tube ) and 0.77" (6" tube). This would correspond to moon structures between 1.5 and 2.2 km, which is considerably smaller than I can achieve in practice. Now the question is, whether my eye is able to resolve that. To answer this, I need to know which magnification is used, because depending on which resolution I assume for the eye, the moon structures have to be between 20" and 60" in size so that I can recognize them.

Let us assume a magnification of 100 x, a field of view for the moon of about 30' (0.5°) = 1800" and a diameter of 3476 km for the moon. Thus, we get 50° = 3000', spread over 3476 km. This results in 1.16 km for one arc minute and 0.39 km for the theoretical resolution value of 20". This is better than what my telescopes are able to resolve. So let us have a closer look! The following table calculates these values for different combinations of my telescopes and eyepieces:

Telescope Aperture Resolving
Power (Dawes)
Max. Usab.
Magnification
Focal Length
of Telescope
FL of
Eyepiece
Magni-
fication
Enlarged
Diameter '
km for
1' 20"
Skymax-102 102 1.15" 153/204*
1300
32
40.63
1218.75
2.85
0.95
24
54.17
1625.00
2.14
0.71
7
185.71
5571.43
0.62
0.21
Skymax-127 127 0.91" 190.5/254*
1500
32
46.88
1406.25
2.47
0.82
24
62.50
1875.00
1.85
0.62
7
214.29
6428.57
0.54
0.18
Explorer 150PDS 150 0.77" 225
750
32
23.44
703.13
4.94
1.65
24
31.25
937.50
3.71
1.24
16
46.88
1406.25
2.47
0.82
7
107.14
3214.29
1.08
0.36

*) While for Newton tubes, a factor of 1.5 is used, for refractors and Maksutov-Cassegrain tubes a factor of 2 is usually used - but not always (in their book Moonhopper, Spix & Gasparini use 1.5 x for all telescope types).

Using the 32 mm eyepiece, which allows me to attach cameras firmly, I get a range of 2.5 to 5 km, while using the 7 mm eyepiece (1:50 method), I get a range between 0.5 km and 1 km. This means that when using eyepieces with a long focal length, I can only achieve about half of the resolution with my eyes that the telescopes can achieve theoretically (this applies to a 1' resolution capacity!). However, for eyepieces with a short focal length my eyes are superior to my telescopes. This is also better than I am able to achieve with my cameras in practice (see below). Theoretically, however, the resolution of my cameras using the 1:50 or projection method is higher. I will try to find some small craters when the moon will show up again to check these calculation results in practice...

What Does the Atik Infinity Camera See on the Moon?

This depends, of course, on the telescope used. When I took a phote of the crescent moon with my Explorer 150PDS, the diameter of the moon was about 1080 pixels, which corresponds to 1800" or 3476 km. Thus, 1 pixel corresponds to 1.67" or 3.22 km. This is almost double the resolution of my telescopes. Thus, the Atik Infinity camera does not exploit the telescope resolution.

A few measurements:

These estimates are plausible. Better accuracy is achieved with large craters. The small craters are used to determine the resolution limit.

What Does a Digital Camera See on the Moon?

I took most of my moon photos with a camera held or attached to the eyepiece. Here I discuss two photos taken with the Ricoh GR (16 megapixels, APS-C sensor) on the Skymax-102 and Skymax-127 (for the photos see below).

R0048031 (GR, Skymax-102)

Moon diameter approx. 2000 pixels corresponding to 1800" or 3476 km >> 1 pixel corresponds to 0.9" or 1.74 km
This is more or less the telescope resolution, that is, the camera fits the telescope (the used Skymax-102 has a resolution of 1.15", the 150PDS one of 0.77").

Measurements:

R0048106 (GR, Skymax-127)

Moon diameter approx. 2650 pixels corresponding to 1800" or 3476 km >> 1 pixel corresponds to 0.68" or 1.31 km

This is a little bit better than the telescope resolution, that is, the camera fits approximately the telescope (the Skymax-127 used has a resolution of 0.91", the 150PDS has a resolution of 0.77").

Measurements:

These estimates are plausible. Higher accuracy is achieved with large craters, the small craters are, however, needed to determine the resolution limit.

Detail Photos

After a little more searching and viewing of the original photos I found (preliminarily) out that objects between 5-7 km diameter can be "guessed" and objects of 8 km diameter or more can be recognized (see photos below). This is certainly only true for the better photos like the ones below.

    

100% section

 

Examples of small craters with diameters in km

    

100% section

 

Examples of small craters with diameters in km

Photo data: February 23, 2018, Sky-Watcher Skymax-102 telescope, Ricoh GR held to the eyepiece

    

100% section

 

Examples of small craters with diameters in km

Photo data: February 23, 2018, Sky-Watcher Skymax-127 telescope, Ricoh GR held to the eyepiece; the shape of cater Müller is reproduced better than on the photo above

 

Software

Virtual Moon Atlas

The Virtual Moon Atlas is a great piece of open source software, but perhaps a little outdated. And it is not as "attractive" as Moon Globe (see below). Nevertheless, it is useful for me, because it provids me with information that Moon Globe does not deliver, especially the names of small caters and information about them.

The last update was in 2012 and my Macintosh version does not run at all. Luckily, I can also run Windows on my Macintosh computer and so I use the Windows version. From time to time, however, it freezes on my computer, and I habe to restart AtLun, which is the moon atlas.

    

Thewhole moon...

 

... and a section at maximum magnification

Moon Globe (HD)

Moon Globe (HD) is a 3D simulation of earth's moon that you can manipulate with the multitouch screen. It features realistic realtime lighting, a catalog of lunar features, and a compass to show the Sun and Moon's position in the sky (from the developer's Website).

I personally think that this is a great piece of software for exploring the moon. I also bought the HD version.

    

Lower magnification, similar regio as above

 

Higher magnification

   

At the terminator - not as pronounced as in reality...

 

References

 

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gerd (at) waloszek (dot) de

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made by walodesign on a mac!
01.04.2018