Lorenzo Zago, firstname.lastname@example.org,
Sun Feb 26 22:57:31 GMT+0100 1995
It may be useful to note that the VLT is just one case of the
extraordinary development of new large astronomical telescopes which is now taking
At the time of writing this report, there are, beside the VLT,
several other ongoing projects:
Other large telescope projects are still in an earlier planning
phase, such as the Columbus project for a telescope with a double
"binocular" mount with two 8-m mirrors, and several national projects
in Germany, Spain and England.
- The first Keck 10-m telescope is completed on Hawaii island
and in the tuning phase, while a twin telescope is being fabricated.
- The american Gemini project for two identical 8-m telescopes for
different sites (Hawaii and Chile)
- The japanese Subaru
8-m telescope project, also to be located on Hawaii.
- The american privately funded Magellan project for a 6-m
telescope in Chile.
99#99 is often called airmass in the astronomical
See footnote at page .
- Including the total seeing contribution.
The 2.2-m building includes a cooled floor while the 3.6-m
now has an active air cooling system in the dome.
- The SuperIMAQ program [ESO]
was written by
Ph. Diericks of ESO to compute the PSF and all image quality
parameters of a telescope mirror,
accounting for all diffraction effects, surface wavefront errors and
seeing by the method described in [Diericks].
- Mirror seeing is treated extensively in section
See for instance [Incoprera], p. 506.
- The wavefront of light
is reflected by the primary mirror toward the secondary mirror
and then again downwards to an instrument focus
(see fig. ).
The DIMM is special 35-cm telescope
for measuring seeing located in open air on a 6-m high tower
(cf. also page ).
see footnote at page .
- In that case the
DIMM was located 2 meters above the ground, 40 m south (downwind)
of the NTT.
- See fig.
- See for instance [Incoprera], p. 506.
We recall that seeing contributions along the line of sight add up
with the power 5/3, while all other contributions add quadratically to
the total seeing (cf. equations () and
- Only the lower atmospheric pressure of an astronomical
mountain site was considered here (770 mb with respect to 1000 mb
for the wind tunnel).
may recall that turbulence frequencies are increased inversely to
the geometrical scale: as a
comparison the velocity spectra are generally measured up to 200 Hz.
- This is the case at the Paranal site of
the VLT ([Sarazin 90]).
- The mirror cooling system should
ideally allow the mirror to remain always slight colder than ambient
air without overcooling it, in order to avoid water condensation.
During the observations,
the mirror can only be cooled from the back side and, because of
its thermal inertia, there will be inevitably
instances when the air temperature will drop during the night to a
lower temperature than the front surface.