The main drawback is a lower limiting magnitude in the case of small holes, and this method can only be used for objects with $V < 8$ at the TBL.

to

[*3.3. Coronagraphic mode*]{}

10000 PISCO can be used as a Lyot’s coronagraph by putting adequate masks $m_1$ in the entrance image plane (I1) and $m_2$ in the pupil plane (P1) (wheels EN and MA of Fig. ). This mode was successfully tested in 1994 with long integrations on a conventional CCD detector. Speckle imaging from short-exposured frames has little interest in this mode since the obturation of the mask $m_1$ in (I1) needs to be quite large (a few times the FWHM seeing) to hide most of the brightness of the central target. This mode would take its real advantage with adaptive optics and a small obturation of $m_1$, to investigate closer to the target (see f.i., some recent developments with a phase mask in the image plane, Roddier & Roddier, 1997).

A four-hole pupil mask can also be used to suppress the diffraction image of the spider of the telescope. This reduces the diffusion of a bright object and allows the detection of a possible faint close companion 