3 Reduction method

We have one conditional equation for each observation:

$$({\rm O-C})(-\sin Z~.~\cos\phi) =$$

$$= 1/15 [({\rm UT0 - UTC})-\Delta L]\sin Z ~.~\cos\phi {+} \Delta\phi~.~\cos Z {+} R$$

$$- \Delta\alpha .\sin Z~.~\cos\phi - \Delta\delta ~.~\cos S$$ (1)

where: UT0 - UTC, $\Delta L$ and $\Delta\phi$ represent the deviations related to the pole motion and the Earth rotation velocity; R is related to the zenith distance correction.

We obtain the residual (O - C) after the groups reduction for each star passage (east and west).