3 Reductions

High proper motion stars were identified blinking the first epoch plates against the second epoch plates with a Zeiss-Jena plate comparator.

Being M_x the motion detected in x between the first and second epoch observations, and T the time base between both epochs, the annual proper motion in x, m_x will be:

$$M_{x} + ax + by + cx^{2} + dxy + ey^{2} + f = m_x \times T.$$

An analogous relation gives the annual proper motion in y, m_y.

To determine the constants in the above relations, 35 to 45 uniformly distributed $\sim$ 16th magnitude background stars with no evident proper motion were adopted as reference stars in each area. Reference stars whose calculated proper motions turned out to exceed 0.5$\hbox{$^{\prime\prime}$}$ during T were rejected in the final reductions.

The positions of the newly discovered high proper motion stars were determined from the second epoch plates, relative to a subset of the Hipparcos Catalogue stars present in each field. Although on the average roughly 60 measurable catalogue stars could be identified in the fields, considering that ultimate positional precision was not in the scope of the present work, only the best distributed ones were used for the reductions. This number varied between 30 and 40.

The plates were measured to $1\mu$ (0.1$\hbox{$^{\prime\prime}$}$ at the plate scale) with a digital Zeiss-Jena Ascorecord measuring machine. Only one setting was made on all stars (catalogue, background and target). Six term (const., X, Y, XY, X², Y²) quadratic relations were used in the reductions. Third order terms were not included because the flat field of the Maksutov Astrograph is almost free of distortions. Also, since all plates were taken near culmination, refraction third order terms were not important.