Guiding and collimation (LBC-style)

The LBCs do not use the autoguiding and wavefront sensing (AGw) units like the LUCI and MODS instruments. Instead, autoguiding is done using stars on the tech chip #1 (see Focal Plane Layout) and focus and collimation are achieved through use of the Focal Plane Imaging Analysis (FPIA) procedure and maintained through the telescope metrology system (TMS).

• LBC Guiding is described here.
• The method to focus and collimate is described in LBC Active Optics; and
• TMS is described here.

Use of TMS during LBC observations started only in 2021. The TMS consists of a set of IR-laser trusses whose lengths are maintained to within 5 microns over time and over slews from object to object. By keeping the relative position of the primary mirror and LBC hub fixed, TMS removes some factors that have affected LBC image quality and allows a deeper study of aberrations that result from thermal gradients and shape changes in the optics themselves. A more thorough description of TMS and an outline of how to use the system when observing with the LBCs can be found here.