N

With the radial push force function fr <x 1 + cos 0 shown in Fig. 8.10-D, we have 5 = 0.

With the equi-spaced push-pull forces Fxn = —W/Nl, Fyn = 0 in Fig. 8.10-C, ¡5 = 0.5.

For the 8.2-m VLT meniscus mirror at f/1.8 with aspect ratio t/2a = 1/47, compared to the two latter distributions by Mack, it was found that if the tangential forces Ft,n are given a certain geometry so that ¡5 ~ 0.75, then the flexure is substantially reduced [74]. The lateral forces act along a circle located somewhere between the rear and midpoint edge of the mirror. This circle is in a plane which does not pass through the center of gravity. Therefore, the final acting forces were given small Fz,n force components to recover the static moment equilibrium which, then, avoids use of lateral forces at the inner contour of the hole. The primary mirror lateral support of the Eso-Vlt is with Nl = 48 forces equally spaced at the outer contour (Fig. 8.12). The force distribution Fr,n, Ft,n that generates the shear function is obtained by hydraulic levers acting on extra-peripheral pivots. Each pivot pad is sealed

Fig. 8.12 Equal-spacing push-pull force distribution for the lateral support of the 8.2 m primary mirrors of the Eso-Vlt. Frn, Ftn forces are with increased shear components 5 = 0.7529 generated via extra-peripheral pad pivots lying in a circle. Because this circle is off-plane to the center of gravity, the final forces are inclined by addition of Fz,n components [74]

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