With the help of Wipneus, I now received my Petermann and Zachariae images printed on canvas and the result is fantastic, thanks Wipneus!!
The Petermann image is 1,3m x 1,3m
The Zachariae image is 1m x 1,5 m
The Petermann image even got a 3D effect (not intentionally).
The images are seen below (in reduced format).
The resolution is even so good I found new details I was not aware of.