Optical coating: (C)-It means that only one or more lens surfaces have anti-reflection coating;
Fully Coated: (FC)-means that all glass surfaces in contact with air have been coated (in most cases this means less, if most plastic lenses are used, there will be no coating
Multi-layer coating: (MC)-One or more lens surfaces have been coated with multiple layers. Some lens surfaces may only be coated with a single layer or some have no coating at all
Full multi-layer coating: (FMC)-all glass surfaces in contact with air have multi-layer coatings
If you have more money on hand, buy a fully multi-layer coated telescope, because this type of telescope has a higher light transmission and clearer imaging. This is why the price of a fully multi-layer coated telescope is higher than the price of ordinary telescopes. High reason.