the art will appreciate that if the operational and design requirements dictate the need for a chamber optics platform whose total mass is such that thermal or other stresses are not rendered insignificant and which would affect the platform 39 s stability as a result of the constraints imposed by the ball cup joint described herein that modifications at each point can be made to free movement along the required degree of freedom for example with one of the three points fixed by a ball cup joint as described herein the second and third mounts could incorporate a cup and roller combination or a 34 v 34 groove to allow movement along the line segments which define the isosceles triangle created by the attachment points those skilled in the art will recognize that these alternative mounts are only two examples of attachment methods which would allow the chamber optics platform to move along the required degrees of freedom in reaction to thermal or other forces and that other equivalent arrangements are available referring now to fig3 a ball cup joint 190 is shown as an exploded close up comprising a threaded shaft 191 leveling means and locking device comprising a washer 192 and jam nut 193 threaded onto shaft 191 cup element 194 is mounted on floating pin 195 housed in cup housing 196 washer 197 is mounted inside cup element 194 atop floating pin 195 to provide support for the cup element when cup housing 196 and pin engagement screw 199 are threaded into engagement with flange 198 and floating pin 195 respectively bolts 200 secure flange 198 to the underside of chamber optics platform 150 not shown fig3 b showing ball cup joint mounting along section lines a a of fig2 d depicts threaded shaft 191 of.