From: "Bianco Giuseppe" 
To: 
Reply-To: "Bianco Giuseppe" 


This is a multi-part message in MIME format.

------_=_NextPart_001_01C3146B.C69802F5
Content-Type: text/plain;
        charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

Even if I've a PhD in Astronomy and reasonable knowledge in optics, I'm =
puzzled by something which will be certainly solved by somebody in the =
list.
Textbooks on mirror making say that, in order to "parabolize" a
concave = spherical mirror, one should dig into the center of the surface;
= conversely, in order to "hyperbolize" a convex spherical
mirror, one = should depress the outer zones of the surface. To me, both
those action = lead straight to an ellipsoidal figure. In fact, in the case
of a = concave surface, a paraboloid results from flattening the outer
zones = with respect to the center, and even more so in the case of an =
hyperboloid.
Where's the trick? Thank you all in advance.

Dr. Giuseppe Bianco
Centro di Geodesia Spaziale "G. Colombo" Agenzia Spaziale Italiana
75100 Matera (MT), Italy
phone:+39-0835-377209
fax:     +39-0835-339005
e-mail: giuseppe.bianco{at}asi.it


------_=_NextPart_001_01C3146B.C69802F5
Content-Type: text/html;
        charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable






dumb question, maybe




Even if I've a PhD
in Astronomy and =
reasonable knowledge in optics, I'm puzzled by something which will be =
certainly solved by somebody in the list.

Textbooks on mirror
making say that, in =
order to "parabolize" a concave spherical mirror, one
should = dig into the center of the surface; conversely, in order to =
"hyperbolize" a convex spherical mirror, one should depress =
the outer zones of the surface. To me, both those action lead straight = to
an ellipsoidal figure. In fact, in the case of a concave surface, a =
paraboloid results from flattening the outer zones with respect to the =
center, and even more so in the case of an
hyperboloid.

Where's the trick?
Thank you all in =
advance.


Dr. Giuseppe
Bianco

Centro di Geodesia
Spaziale "G. =
Colombo"

Agenzia Spaziale
Italiana

75100 Matera (MT),
Italy

phone:+39-0835-377209

fax:     =
+39-0835-339005

e-mail:
giuseppe.bianco{at}asi.it




------_=_NextPart_001_01C3146B.C69802F5--

--- BBBS/NT v4.00 MP