The design uses a 45 flat secondary mirror to view the image, as in a standard Newtonian telescope.
A small secondary mirror focussed the image from the primary into a 35 mm movie camera, which captured the images on film.
Newtonians have a central obstruction due to the secondary mirror in the light path.
The comparatively small secondary mirror is 2.74 m in diameter, which will serve active corrections.
A centrally-placed secondary mirror and usually an additional small lens group bring the light to focus.
In late 2002, a novel deformable secondary mirror was added to the telescope.
The f/ratio is long to have a small secondary mirror, again to minimize the telescope's thermal emission.
This was to allow the same cell to measure both selective and full field for which the secondary mirror was larger than earlier cameras.
It has been upgraded, including the installation of a new secondary mirror.
They are artifacts caused by light diffracting around the support vanes of the secondary mirror.
