What is the role of the lens coating? There are several coating methods? How are they different? If the eyepiece is also used multi-layer coating is not that more advanced?
The coating is a kind of technical treatment to prevent the light reflected from the damage caused by the impact. Fine coating is often used chemical treatment, so plated film is not easy to wipe off, the coating also appears to be natural and gentle. According to the process of coating in the optical sight is divided into single-layer coating and multilayer coating (MC).
Optical aiming mirror coating with a single layer of blue film is the most common, but also a few share the use of multi-layer coating. Multi-layer coating can better reduce the various wavelengths of light on the lens reflectivity, in order to improve the overall sight of the color reproduction. The simplest way to distinguish is: single-layer coated lenses reflect a single color in daylight. The multi-coated lenses in different positions show a variety of colors under the gentle reflective (different from the Daxing Russian telescope on the street that big reddish green thing).
Because of the direct light, so if a good mirror objective multilayer coating has done very good, then there is no need to multilayer coating on the eyepiece, the general all coated mirror eyepiece has also been coated, the general eyepiece coating is a single film. The coating method must be able to distinguish between the multi-layer coating and the nature of single-layer coating, so as not to be deceived (the best coating is "green broadband coating," which is a kind of high-definition image with the transmittance of super-coating).