Encumeada Alta (Madeira) is known to be one of the best existing dark-sky optical observing sites (Walker, 1984) in the northern hemisphere. At latitude 32 46' and longitude 16 56' , it is located within one of the regions of stable tropical maritime air in the northern hemisphere, the same as Canary Islands, were there is often a well developed inversion layer with the basis at approximately 1000 m above sea level and the top about 400 m above the base of the inversion (Walker, 1984).
It is one of the sites tested in the 70's for the "Northern Observatory site testing project" and McInnes (1981) provides month-by-month percentages of hours with seeing 1" while Walker (1984) compares with various other sites around the world.
At an altitude 1784 m, Encumeada Alta presents to the north a smooth and convex surface open to the prevailing wind from the ocean, in the north-west direction and due to its location it is expected to be much less affected by the Sahara dust than the Canary Islands.
There is no record of seismic activity in Madeira. Encumeada Alta is located within a protected area (natural park) free from industrial or light pollution. There is no large city or sizable commercial or tourist development on the northern coast - up to now the main development is on the southern coast of Madeira and Encumeada Alta is protected by the high ridges to the south of the site. There is very good connection between Madeira and the main European cities by regular commercial flights.
A feasibility study for the development of an astronomical observatory in Madeira - a national facility open to international collaboration - was undertaken in the beginning of 1994 at request of the Portuguese government. The report was approved and successfully used for funding application both to european funds for regional development and national funds in 1995. The following step, a detailed proposal (including the set-up of the observatory and associated facilities on the site as well as the creation of a research support Institute in Funchal) was submitted still in 1995, also at the government request, at the same time as the administrative and legal organization of the future governing body were looked into. While still waiting approval by the new Minister of Science & Technology, the project is open to proposals for partnership and/or installation of telescopes at this prospective new observatory.

References:
"High Quality Astronomical Sites Around the World", M.F.Walker, 1984, "Site Testing for Future Large Telescopes" ESO Conference and Workshop Proceedin gs n 18, 3.
"Site Testing on Hawaii, Madeira and the Canary Islands", B. McInnes, 1981, Q. Jl. R. astr. Soc., 22, 266.

Teresa Lago
Centro de Astrofisica da Universidade do Porto
Rua Campo Alegre 823, 4150 Porto, Portugal
Tel. 351-2-6007081 Fax 351-2-6007082
e-mail: mtlago@astro.up.pt
Madeira - ESPAS/18 March 96