Advertisement
•
FINE FOCUS
Fitting a motor focus to the fine focus knob can help find & track focus. However unless the motor controller has a
digital read out it can still be a hit & miss affair.
•
FINE FOCUS
OPTEC TCF-S digital focuser
-
MOTORISED FOCUS
-
REMOTE DIGITAL FOCUSER
The focuser I recommend for focusing a DSLR is
the Optec TCF-S temperature compensating
Crayford focuser, with digital read out & PC
remote control. It has a red LED digital read out
and is adjustable in 80 micro-inch steps, over a
0".7000 range.
The technique I use is first focus on a bright
star, checking the image on the LCD view
screen, RAW image @ x19. Then point the
telescope at the object of interest & take a
sample shot. Check the focus on the LCD screen
@ x19 & make systematic adjustments in 10 &
then 5 step increments until the focus is as
sharp as the seeing permits. Because there is
backlash in the spur gear train between the
stepper motor and the Crayford focus spindle,
(~±20 steps) you must rack in @ 10 or 5 step
increments until it is evident the focus is
becoming worse, and then backtrack until you
home in on the sharpest possible focus. Seeing
will limit your ability to locate the precise focal
plane.
Advertisement
