For filters whose appearance cannot be directly distinguished, users can identify them by capturing characteristic nebulae

1.Compared to filters with a thickness of 2mm or 1.85mm, filters with a thickness of 3mm require a longer back focal length, usually calculated at one-third of the thickness. For example, a 2mm thick filter  2/3+55=55.66mm, and 3mm thick filter with a back focal length of 3/3+55=56mm.

2.During the use of the filter, there may be varying degrees of stress due to the filter wheel and pressure ring not being parallel or the pressure ring being too tight, as well as thermal expansion and contraction. Thicker filters can significantly reduce stress

For light with larger incident angles, the wavelength band of the filter will shift blue.
For example the incident angle is 0 ° and the center passing band is Ha 500.7nm, increasing the incident angle of the light to 5 ° may result in the center passing band of the filter being 500nm