Telescopes for advanced users are recommended for those who want to engage in the detailed observation of the sky. These can be experienced observers, but also committed beginners who want to invest in a larger instrument right from the start.
Telescopes for advanced users are not necessarily complete systems. This applies in particular to OTAs. This acronym stands for optical tube sssembly and means a telescope without a mount.
Telescopes with an aperture of 12 inches (305 millimeters) or more are also classified as "recommended for advanced users” since they are somewhat more complicated to handle. Also in this category are telescopes designed primarily for astrophotography, such as Newtonian telescopes for photography, RC telescopes and apochromatic refractors.
The classification according to beginners, advanced and for observatories is for orientation and is not meant to rule out or exclude in any way.