A mirror cell supports the primary mirror of a telescope against gravity.
It shall do that in a way that avoids deflections by the mirrors
own weight forces. Most commercial mirror cells are
optimized for cheap production with an approach similiar
to "one size fits all", i.e. they offer a set of designs
each roughly adapted to a range of mirror sizes.
To get the most out of a fine mirror, it is worth while,
to consider the real nature of the problem:
- Every mirror size requires it's correct cell size.
- Mirrors with a bore behave differently than full ones.
- The part of a primary mirror occluded by the secondary is not
relevant for the optical quality of the system.
- Lateral forces deflect the mirror, when the telescope is tilted.
It makes a difference, whether the mirror is thick or thin.
The larger the mirror, the more support points are needed to
keep deflections low. But it's not only the number, the distribution
of the support points is of allmost equal importance. Using
FEM optimization, I found a new distribution for nine support
points, very different from the common system, that gives
much less disturbing deflections for a typical Newtonian telescope.
Worth mentioning, the mirror cells we produce are of good mechanical
design, providing for minimal image shift, when the telescope
is tilted. Close attention has been used on good thermal behaviour
of the cell and uniform cooling of the mirror.