Ganymede, the largest of the four Galilean moons  with a diameter of
5262km, appears as tiny disk about 1.8 arcseconds in calm air. This is
enough to be able to perceive vague surface shading with large telescopes
under favorable conditions. In order to display a more detailed map, I used
the Lucky Imaging process, using a high- resolution video camera.

An 18" Dosonian telescope was used on an equatorial platform in combination
with a coma corrector, Barlow lens, infrared/UV cut filter, atmospheric
Dispersion corrector, and a color video camera with small pixels.

Videos with a high number of frames, short individual exposure times and
small image sections were stacked and sharpened using various freely
available programs. Without the extremely quiet and numerous nights with
excellent seeing over Central Europe, especially in the summer of 2023,
this high resolution would not have been possible.

The large dark regions and the light trenches can easily be recognised in
the photos. By turning the brightness up, numerous bright spots become
visible, which can often be assigned to Ganymed's craters in space probes
images.

A lot of shots were necessary to photograph all areas around the moon.

I drew the map by hand, using freely available software, mostly ignoring
obvious artefacts in the photos but documenting as many actual detail as
possible.

I dedicate this map to all active planetary observers and photographers.
Although it is if course not as detailed as NASA maps, it shows what is
achievable for the committed amateur astronomer today. 

[Mike Wolle : Austria ]