Advanced CT Laser Collimator Manual (V9.0 =OH=) Page 16 of 20
b. Accessory Focuser DrawTube Tilt Setscrews – MoonLite telescope accessories
CHL MODEL 2.5” Focusers
with draw
tube tilt adjustment setscrews. These focusers are available for all Celestron Edge telescopes for use with and without the
dedicated Celestron reducers installed, and for other telescope brands. The CHL focuser draw tube tilt adjustment has
greater tilt adjustment range and maintains the rotational feature between the telescope-side fixed flange and the top
flange (eyepiece/camera) side flange. The draw tube tilt setscrews are set cross-wise to the optical axis. The CHL focuser
has both older style flange tilt setscrews, and draw tube tilt setscrews. This is necessary because the flange tilt setscrews
have special self-lubricating delrin bearing tip material that allows the rotational feature to function.
When the draw tube tilt is adjusted to accomplish
Step 11.1.d & .h
the focuser must maintain the same orientation on the
telescope rear cell when it is removed and installed – the tilt adjustment will be incorrect in any other orientation. However,
leave the flange rotational feature functional, and when installing accessory reducers or flatteners rotate the focuser to the
orientation where tilt adjustment is correct and lock it down again in the correct orientation when using the accessories.
When not using the accessories, again, rotate the focuser to the correct orientation.
(To re-square the flanges after inadvertent flange tilt setscrew adjustment: use a feeler gauge set to check the gap
between the flanges and adjust the gap with the flange tilt setscrews until the gap is the same all the way around, and
rotation is free with no play between the flanges.)
Adjusting tilt using the MoonLite CHL focuser draw tube setscrews:
1. Maximum CHL DrawTube setscrew adjustments will be on the order of less
than one-half turn, and most adjustment will be small increments of a turn.
2. Determining which of the four setscrews to adjust first is strictly trial and error.
Get the feel of how much torque is on each of the setscrews. Put the 5/64” allen
wrench into any setscrew and note its position, then turn it in (CW) a bit while
noting how much torque is on the setscrew; also observe if Tilt alignment is
better or worse, then return it to the start position. Do this for all four setscrews
getting a feel for a normal range of torque values that can be expected. (Torque
on a setscrew represents force to hold metal into a position; it does not
represent load applied to a bearing.)
3. When the tilt is completely adjusted the setscrews will have varying torque and
this is OK and expected. However, all setscrews should have some minimum
torque. If backing out a setscrew (CCW) improves tilt alignment to the point that
all torque is lost, turn it back in (CW) until the first movement of tilt alignment is
observed and stop – this is the minimum torque required. Then proceed using
the other setscrews to continue adjusting the tilt alignment. More adjustment
will be available using the other setscrews. The CHL 2.5” Focuser allows more
Tilt adjustment than was available with previous focusers.
4. When Tilt adjustment is complete, some setscrews will require much more
torque than others to bring everything into alignment.
CHL focuser draw tube tilt
setscrews
c. Visual Back Shim – Final optical tilt axis adjustment with a visual back is typically done with wedge shims between the
telescope rear cell threaded mounting flange (rear surface) and the mating surface of the visual back where it butts up
against the rear cell flange. (Some telescope accessory makers offer specialized visual backs with a tilt adjustment.) To
create a wedge shim for the tilt adjustment, Mylar tape (like Scotch 3M #600 transparent tape), can be placed on the visual
back - rear flange mating surface (a single piece or in layers as needed), and trimmed to size with a No. 11 Exacto blade.
After applying the tape, when installing the visual back on the rear cell, hold it up against the telescope rear flange and do
not let the visual back turn when tightening the large nut (B-nut) that secures the visual back to the rear cell. By applying
the Mylar tape to the visual back flange the tilt shim can be rotated to different positions. However, to prevent tape peeling
problems, it is recommended to loosen the B-nut sufficiently to lift the visual back away from of the rear cell flange before
rotating it to a new position.
d. Tilt Adjustable Reflector Mirror – Use the instructions supplied with the accessory to adjust Tilt.
11.3. Mechanical Systems Used for Corrector Plate Adjustment
This step will cover the mechanics of moving the corrector plate in lateral directions to achieve adjustment. The necessary
checks and observations that must be made to achieve centering are presented in
Step 11.1.g
.
PRECAUTION – Use care working around the corrector plate. Work so as not to touch it or get finger prints on it. Use a lens
blower and/or a soft camel hair lens brush to remove any dust, pollen, and debris before starting. If an aerosol blower is used,
do not tip it on its side so much that liquid propellant is discharged on the telescope parts. Use care to prevent debris from
falling into the telescope tube.
a. Direction to move the corrector plate for adjustment – The push or pull direction is the same when observing either the
collimator target plate or the reflector mirror target: Visualize the center of the collimating lasers’ three dots or focused
single laser dot – the dot or dots move toward the direction from which the corrector plate is pushed, or conversely away
from the direction the corrector plate is pulled. (To move the dots – push to fetch or pull to repel.)