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