Guider Conversions

The guider generates centroids in the pointing origin coordinate system (as offsets relative to the center of the guider detector). These positions have to be rotated to the telescope (Az,El) coordinate system. This is illustrated in See Guider Centroid Conversions , which is simply the central section of See Telescope Offset Conversions (ignoring on-sky scaling issues) .

FIGURE 7. Guider Centroid Conversions

Guider centroids can also be used for other purposes:

• to adjust collimation coefficients (e.g. the xguide CENTER command); same transformation but results stored in different variables
• to adjust pointing origin definitions (e.g. the xguide CENTER command when the "Center by adjusting pointing origin?" button has been checked); no transformation required, already in correct coordinate system
• to offset the telescope (RA,Dec) (e.g. the xguide GOTO command); same transformation, followed by Az flip and PARANG rotation to (RA,Dec) (see See Telescope Offset Conversions (ignoring on-sky scaling issues) )