Focuser Parallelism; Balancing The Tube With A Heavy Image Train - SKY-WATCHER Quattro-200 ST Instruction Manual

Focuser parallelism

Fig. 6

Balancing the tube with a heavy image train

Since the Quattro Newtonian telescope is very well suited
for wide field photography, the focuser of this telescope is
equipped with adjustment screws for alignment of the
focuser to the optical axis of the telescope. Misalignment
can be detected in the edge of wide field pictures when
the stars in the 4 edges look different. The stars in the
edges may show some coma if the optional coma
corrector is not correcting all of the coma aberration in the
image edge of a very big size CCD, but this aberration
should be symmetric (all pointing to the center of the
image). If not, realigning the focuser with the push pull
screws ([Fig. 6 A
In Newtonian reflectors the secondary mirror intercepts the
light and points it out the side of the tube at right angles to
the tube through the eyepiece.
This configuration allows positioning the eyepiece in a
comfortable viewing angle, mainly parallel to the ground or
elevated some degrees when the target is low on horizon.
When using an accessory in the focuser, like an eyepiece,
the tube is not in perfect balance due to the added weight of
the eyepiece on one side of the tube. It has no real
importance when the accessory is light, the mount can
easily support such imbalance.
When using a heavy imaging train, containing a heavy CCD
Fig. 7
camera, a radial guider, a filter wheel and maybe an adaptive
optic system the imbalance can become a real problem.
A neat solution to this imbalance problem is to put all the
imaging train vertically, oriented to the ground, as shown in
[Fig. 7].
I
N THIS CONFIGURATION GRAVITY IS YOUR ENEMY
CAREFUL TO PROPERLY SECURE YOUR ACCESSORIES
TO THE FOCUSER
Part IV: Advanced Operations
and B]) may be needed.
F
INE TUNING THE FOCUSER PARALLELISM IS A
DELICATE OPERATION
FOR OTHER CAUSES BEFORE ATTEMPTING THIS
.
PROCEDURE
!
9
. P
LEASE CAREFULLY CHECK
! B
E