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