miniature helical focuser and
1-1/4" nosepiece constitute a nice enhancement
to SBIG's CCD camera efinder, typically used for
autoguiding without a guidescope.
SBIG efinder Focuser Enhancement
The standard hardware supplied by SBIG includes
the 1-1/4" nosepiece (standard with the CCD camera),
efinder lens, extension tube, and efinder barrel.
In efinder configuration, the 1-1/4" nosepiece is
not used. Instead the efinder barrel is screwed
directly into the CCD head and the efinder lens and
extension barrel combination is held in place
on the opposite end of the barrel with nylon
With the standard SBIG configuration,
focusing is done by loosening the
thumbscrews and sliding the lens assembly in
and out. At best, this is a clumsy two-handed
procedure which must be done while watching the
CCD imager's output on a screen. In cold
weather, this is extremely difficult to do with
To add the Borg helical focuser, put the SBIG-supplied
1-1/4" nosepiece on the CCD head. Then slide the Borg
focuser assembly onto the SBIG assembly, pushing it
all the way in before tightening the two chrome-plated
Finally, screw the SBIG lens assembly into the nose of
the Borg assembly but do not include the
extension tube. The lens may not screw completely in.
In this case, do not force the lens on, but screw it in
far enough to insure a secure fit.
When using the completed setup, infinity focus
should be reached with the helical focuser at
about the middle of its range of travel. Note
the focuser scale readings and tighten the
focuser lock screw after achieving critical
focus. In the future, the focuser reading
recorded can be used to rapidly come close to focus
even if the assembly has been taken apart.