2. Observational material, reduction procedure and errors

The areas were exposed 30 minutes on Kodak 103a-0 plates and some of the second epoch were exposed 40 minutes on baked Kodak IIIa-J plates. All of them, near culmination and in good seeing conditions.

The LTT stars were identified with a Zeiss Jena plate blink comparator, and their coordinates were determined to 1 micron (0.1 arcsec at the plate scale) with the two coordinates Zeiss Jena Ascorecord measuring machine, both of the Observatorio Astronómico de Cerro Calán.

Table 1 (click here) gives the coordinates of the centers of the areas and the epochs of observation of the plates.

 

Nr. R.A.(1950.0)DEC. PAIR 1 PAIR 2 Nr. R.A.(1950.0)DEC. PAIR 1 PAIR 2

1 00 07.9 -25 27 1969.53 1993.80 1969.83 1993.87 60 09 09.1 -14 36 1970.02 1993.06 1970.08 1994.10

4 00 38.0 -14 09 1969.60 1992.81 1969.84 1993.80 61 09 10.1 -23 58 1970.02 1992.10 1970.09 1994.11

6 00 43.6 -25 28 1969.53 1993.80 1969.83 1993.87 62 09 15.8 -16 12 1970.03 1993.06 1970.09 1994.04

7 00 48.4 -07 21 1969.84 1993.87 1969.85 1993.95 63 09 21.2 -22 58 1970.01 1993.07 1970.33 1994.10

13 01 30.3 -07 17 1969.84 1992.81 1969.91 1993.95 64 09 24.0 -11 47 1970.02 1994.04 1970.03 1994.11

15 01 33.9 -29 17 1969.84 1990.88 1969.93 1991.85 66 09 41.6 -20 39 1970.09 1994.10 1970.11 1994.11

18 01 50.6 -13 59 1969.86 1992.82 1969.94 1993.80 67 09 43.4 -14 08 1970.02 1993.07 1970.11 1994.10

24 02 43.5 -08 02 1969.87 1992.81 1970.66 1993.80 70 09 57.0 -19 16 1970.01 1994.18 1970.09 1994.19

25 03 02.6 -15 48 1969.84 1992.82 1969.93 1993.80 71 10 02.8 -07 28 1970.02 1994.11 1970.03 1994.19

26 03 03.0 -26 07 1969.91 1991.85 1969.93 1993.87 73 10 16.2 -17 44 1969.36 1994.10 1970.03 1994.11

27 03 08.8 -09 07 1969.86 1993.80 1969.99 1993.87 74 10 16.3 -26 27 1969.37 1992.10 1970.04 1994.11

33 03 36.8 -18 44 1969.92 1991.85 1969.99 1992.81 79 10 32.8 -07 00 1970.02 1993.32 1970.32 1994.10

34 03 36.8 -18 44 1969.85 1991.81 1969.93 1993.80 84 11 18.1 -09 58 1970.05 1994.19 1970.33 1994.36

42 04 59.8 -25 10 1970.00 1991.85 1970.01 1993.87 86 11 45.5 -10 41 1970.10 1994.18 1970.32 1994.19

45 05 10.0 -15 31 1969.85 1993.87 1970.02 1993.95 87 11 45.9 -29 10 1970.11 1995.17 1970.25 1995.18

49 06 12.2 -21 34 1969.84 1994.10 1969.87 1994.11 89 12 04.3 -29 33 1970.09 1994.36 1970.11 1995.17

50 06 16.7 -27 21 1969.86 1993.96 1969.87 1993.96 95 12 57.7 -14 35 1969.46 1994.19 1970.42 1994.37

51 06 23.1 -22 24 1969.86 1993.07 1969.93 1993.95 97 13 00.4 -30 18 1969.46 1990.47 1970.10 1991.29

52 06 43.3 -27 05 1969.85 1990.04 1969.87 1993.95 98 13 03.1 -07 45 1970.10 1994.36 1970.11 1994.36

54 07 00.7 -29 00 1969.93 1988.02 1970.02 1988.06 100 13 12.4 -16 04 1970.11 1993.47 1970.13 1994.18

58 08 31.1 -22 48 1970.02 1992.10 1970.02 1993.07 101 13 17.5 -20 57 1970.12 1995.17 1970.27 1995.17

 

In each area, 35 to 40 stars were selected with blue magnitudes about 16, as reference stars and uniformly distributed over the plates. A six terms quadratic equation was used in each coordinate:

and a similar one for y.

M_x is the movement detected in x between the first and second epoch plates of each pairs, m_x is the annual proper motion in x and T is the time base. To determine the constants, the reference stars were selected from those with no detectable proper motion, so that m_x = m_y = 0.

In computing proper motions, reference stars giving residuals equal to or greater than 0.9 arcsec in x or y were discarded. The annual proper motions and were calculated with equinox J2000.0, as reference, which the total proper motions and position angles were determined. The annual proper motions and the position angles given in Table 2 (only available at CDS) are the means of the two values obtained from the plate pairs; 20 LTT stars were common to the overlapped areas mentioned above. For them, the results given in Table 2 (indicated by (*) in column Remark) correspond to the means of the values obtained from four plates pairs. The determination of positions and the computation of errors in proper motions were explained in Wroblewski & Torres (1989).