#19860 - Lacerta for Lodestar Focus Aide
199 Smith Street · Lowell, Michigan 49331 · U.S.A.
Telephone: 616-897-9351 · Fax: (616) 897-8229 · Toll Free: 888-488-0381
Lacerta for Lodestar User’s Guide, Revision 1
Page 2 of 5
How FocusLock Works:
FocusLock operates by continually analyzing the guide camera image for relative roundness of the guide
star. The relative roundness is a measure of focus with signed information showing which side of focus
the camera is currently positioned. By setting the imaging camera and guide camera parfocal, FocusLock
can drive any ASCOM focuser to the ideal focus in real-time without leaving the imaging target.
The diagram below shows the shape of a guide star inside focus, at perfect focus, and outside focus.
Designed as an ASCOM local server application with a pass-through methodology, FocusLock operates
seamlessly and transparently to all other guide and imaging applications. Similar to Optec’s Alt-Az De-
rotation Server software, the ASCOM shim is part of the magic behind FocusLock. As long as the
telescope is guiding, the focus remains locked.
Allowance for Filter Offsets
FocusLock works with most any imaging workflow when an ONAG or OAG is utilized. Filter focus offsets
can be determined once and then stored for automatic focus adjustment when a new filter is moved
into the imaging camera’s light path. Even if the guide camera is not located behind the filter wheel,
focuser offsets can still move the imaging camera to the precise, optimal focal point.
