#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 4 of 5
Two spacers, one approximately 0.8mm thick and another 1.6mm thick, may be used singly or together
to take up any slack under the threads or to adjust the distance of the Lacerta to the imaging sensor as
necessary.
After installation, check to see if the Lacerta is properly seated by gently shaking the camera and listen
for a rattle. The Lacerta flange is less than 1mm thick and is machined precisely to fit the Lodestar body.
Parfocal Adjustments to Main Camera
It is important the Guide camera and main Imaging camera are parfocal. That is, the optical distance to
the center of each imaging sensor should be the same. To accomplish this parfocal adjustment, we
recommend the following steps be done at the telescope.
Step 1 - Focus the Imaging camera:
With the Lacerta installed into the Lodestar, re-assembly your Off-Axis Guider (OAG) and re-attach to
the main Imaging camera. Reinstall on the telescope and adjust your focuser for best focus on the main
Imaging camera. A Bahtinov mask or other diffraction based focus aide can be very helpful in this step.
Step 2 – Adjust the OAG Guide camera focus:
With the main Imaging camera in sharp focus, you now adjust the Lodestar camera for best focus. The
Starlight Xpress OAG allows a simple mechanism to adjust the height of the pick-off mirror stalk to bring
the Lodestar guide camera into sharp focus. You will notice the astigmatism introduced by the Lacerta.
Adjust the off-axis guide star image for the best cross possible by manually adjusting the height of the
pick-off stalk.
For QSI camera owners using the Lodestar guide camera,
Gary Jarrette offers his KISS focuser which makes this step
very simple –
See
https://www.youtube.com/watch?v=YX-nyWe0qp0
Other camera and OAG installations may require other
adjustments but the idea is to ensure the Lodestar guide
camera is in focus when the main Imaging camera is also in
focus.
Step 3 - Find Focuser Offset:
Ideally, the Guide and Imaging cameras are parfocal, but for fine adjustments FocusLock allows an offset
between the two cameras. Open
FocusLock – Settings
and click the Find button in the Find Focuser
Offset panel. Follow the instructions to set the focuser offset between the Guide and Imaging cameras.
