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Mewlon
Dall Kirkham telescope is one
of the Cassegrain optical systems, with a concave
elliptical mirror for the primary and with a convex
spherical mirror for the secondary. The Mewlon is a
new concept telescope that is made in mass
production by virtue of Takahashi's high polishing
technology in having made a great number of various
non-spherical reflecting optical systems.
* Designing concept
The
Mewlon-210 is designed mainly based on the visual
performance that is the basic function of an
astronomical telescope. Therefore, this optical
system can be used better for visual observations
than for taking deep-sky astrophotograph which
requires sharp images over the wide photo field. In
the view field, this optical system can produce so
good images as a Newtonian can do. Therefore, this
can be said to be an ideal telescope to do the
planetary observations as well as to the lunar
observation. Thus, the Mewlon-210 has been developed
as a very compact and highly easy-to-use telescope
by simplifying the aim of the use.
*
Performance
The
Dall Kirkham telescope is a well known and excellent
optical system from the old times. However, it has
been hardly produced as a commercial telescope because
of difficulty of making its primary mirror of a
concave elliptical surface. The image focused in the
center is a very sharp without any aberration like
as in a Newtonian telescope. The images toward the
edge are generally fine within the view field,
although it is sometimes said that some amount of
coma aberration is visible.
In
the astrophotography, especially in highly magnified
lunar and planetary photography, you can expect a
good result with your Mewlon-210. When it is
compared with a traditional Cassegrain telescope,
the Dall Kirkham telescope can be easily assembled
and aligned in the process of production. This
optical system as a highly precision telescope can
maintain stable performance. As mentioned before, it
is so suitable especially for lunar and planetary
observations because its long focal length by a
spherical convex secondary mirror (a parabolic
convex mirror in a Cassegrain) can easily produce
high magnification.
*
Operation
The
handling of your Mewlon is so simple. At first, set
the devo-tail plate under the main tube into the devo-tail
adapter attached on the equatorial mount. The finder
is so firmly attached on the tube that you can hold
the tube by the finder when you set the tube into de
devo-tail adapter.
Your
Mewlon-210 is a Cassegrain type so that the length
of the tube is far shorter than that of a Newtonian
telescope with the same aperture and the same focal
length. Moreover, it is a very compact and
light-weighted, which permits you to use a
relatively smaller equatorial mount. Because of
this, the whole system becomes totally compact and
easy-to-use.
The
optical axis alignment can be made with the three
screws provided in the secondary mirror section.
Once aligned, the optical axis will become hardly
out of order except when a great shock is given to
the telescope.
Focusing is made by the mirror shifting method,
turning the focusing knob clockwise or
counter-clockwise. This system will permit you to
focus smoothly with your fingers when a camera is
attached on the visual back, without giving an extra
load of a camera as in the rack and pinion focusing
system.
From Takahashi Seisakusho
Ltd. product manual (1993) |
