7.4) Collimation and focal plane tip-tilt in the
Veloce
.
To collimate your
Veloce
you have to follow a procedure almost identical to the one described in
Chapter 5, i.e. you will tip-tilp the primary mirror only, working from the
back plate
of the telescope.
The secondary mirror (and the frontal meniscus lens) is fixed during production. The secondary
mirror shadow will obviously show no spokes.
The
Veloce
has a series of screws on the back
plate that you must became confident with.
See the photo at left. You see three BIGGER
screws, 120° apart, for collimation (yellow
arrows), and four SMALLER
couple
of screws,
90° apart, that control the tip-tilt of the focal
plane (green arrows). Their use is described
later in this section.
All the necessary wrenches have been
provided with your
Veloce
. Remember, the
bigger screws are for collimation, and you work
on them with the bigger key (red arrow).
To collimate the
Veloce
you have to follow
exactly the same procedure described in
chapter 5. As a matter of fact, it is more
comfortable to collimate a
Veloce
than other
instruments, because you can work on the
back plate
and
look in the eyepiece at the
same time, the instrument is more compact,
and screws are smaller and require less
torque. Like in all other
Officina Stellare
telescopes, the collimation screws are spring-
loaded, so if you tight one screw there is no need to loosen the other two.
Because of the Riccardi-Honders optical scheme used in the
Veloce
, it is extremely unlikely you
have to turn each collimation screw more than one turn, to reach perfect collimation. If this is the
case, work on
all
screws instead of rotate more than full turn only one screw. This will preserve the
distance between mirrors, that has a quite tight tolerance. Moreover, if you unscrew too much one
of the collimation screws, you could disconnect the main mirror from the tube. Not a tragedy, but a
big nuisance. Ask support Officina Stellare if this happens.
The
Veloce
is a very fast focal ratio astrograph, with a large corrected and illuminated field (42mm
for the RH200). For this reason, if the optical train to the sensor is less than perfect, or the chip is
not perfectly "squared" into the body of the camera (yes, it happens), you can have the unpleasant
situation where the image is perfect in the center of the field, but out-of-focus or with non-pinpoint
stars in one or more of the corners. In this case, you have to fine-tune the tip-tilt regulation of the
focal plane. Four couples of screws are provided for this job. See section 6.6. You can do this
regulation only during night time, with a series of short exposures, acting by trial and error. Each
couple of screws does include a "locking" screw (the smaller one) and the spring-loaded regulation
screw (the bigger one). Look the photo in this page (lower green arrow). The black hex key is in
the regulation screw, the thinner bright one is in the locking screw.
You must unlock all the four "locking" screws, do your trial and error with the four regulation
screws, and then lock again the tip-tilt mechanism, locking (gently) the four locking screws
WARNING: this procedure requires just small movements, for sure under one full turn of
the screws. Do not unscrew the orthogonality adjustment screws too much, as the focuser
or the attached optical train may disconnect from the tube.
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