{HEAD ~ The optical surfaces} have a high value of elastic modulus, reducing coma and {TAIL ~ other aberrations} associated gravity and acceleration 
reducing
{ HEAD ~ The optical surfaces } have a high value of elastic modulus , reducing coma and { TAIL ~ other aberrations } associated gravity and acceleration
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH REL OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH