Mewlon 210: The original focal length of 2415mm and focal ratio of f/11.5 changes to 1961mm focal length and f/9.3 focal ratio. The image circle is now enlarged from 18mm to 39mm and the field of view to using the reducer becomes 1.2 degrees. 

Mewlon 250: The original focal length of 3000mm focal length and focal ratio of f/12 changes to 2307mm focal length and f/9.2 focal ratio. The image circle is increased to 42mm and delivers a 1 degree field of view. 

Mewlon 300: The original focal length of 3572mm changes to 2739mm and the focal length of f/11.9 changes to f/9.1. The image circle is enlarged from 25mm to 42mm and the the field of view becomes 45 arc minutes in diameter.