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11.1 Standard Star Observations

Three standard star fields were observed: M67, PG1633+099, and SA110 centered on star 503 (hereafter SA110-503). The M67 field was observed with the telescope defocused, since the stars in that field are very bright; the other two fields were observed with the telescope focused. Examples of the visual appearance of a defocused and a focused star are shown in Figure [*]. four passbands were used: Gunn r, and Johnson V, B, and U. Standard stars were observed on all the nights that the Hydra galaxies were observed in Gunn r and Johnson B (night 1, 2, 3, 4, & 6), but not the night that the Hydra galaxies were observed in Johnson U (night 9). In addition, standard stars were observed on night 7. Details of the standard star observations are in Table [*] and [*].

Two naming schemes exist for the stars in the M67 field: The F numbers (e.g. F108), and the quadrant numbers (e.g. II20). They are almost, but not completely, disjoint. A finding chart for the F numbered stars is in Johnson & Sandage (1955). A finding chart for the quadrant numbered stars is in Eggen & Sandage (1964). Four stars (of interest to this study) with F numbers, are not marked on the map of Johnson & Sandage (1955), and have also been assigned quadrant numbers by Eggen & Sandage (1964). These are: F93= I12, F106= I11, F128= I198, and F129= I199. The finding chart of Schild 1983, which covers a smaller area than that of Johnson & Sandage (1955), has these 4 stars on it with the F numbers. Also note, that two stars are labeled 124 (i.e. F124) in the map of Johnson & Sandage (1955). The bright one (the one most to the east) is F124, the other one is I10.

Finding charts for the PG1633+099 and the SA110 field are in Landolt (1992).


  \begin{figure}% latex2html id marker 23815\makebox[\textwidth]{ \makebox[\hal... ...is 499 (r = 11.5 mag), the one to the right is 502 (r = 11.4 mag).}\end{figure}


 
Table: Standard star observations, by night
Night Field Airmass Exposure time [sec] Image name (dfsc #)
      GR JV JB JU GR JV JB JU
1 M67 1.33 5 10 20 120 d1263 d1262 d1264 d1266
1 PG1633+099 1.43 10 20 120 300 d1322 d1318 d1320 d1321
1 SA110-503 1.67 4 7 20 240 d1325 d1326 d1327 d1329
1 SA110-503 1.16 3 6 20 90 d1349 d1350 d1351 d1352
2 M67 1.34 5 10 20 120 d1388 d1389 d1390 d1391
2 PG1633+099 1.38 7 20 120 300 d1464 d1465 d1466 d1467
2 SA110-503 1.67 4 7 20 120 d1472 d1469 d1470 d1471
2 SA110-503 1.15 4 7 20 120 d1494 d1495 d1496 d1497
3 M67 1.34 5 10 20 120 d1534 d1535 d1536 d1537
3 PG1633+099 1.42 10 20 120 300 d1597 d1598 d1599 d1600
3 SA110-503 1.68 4 7 20 120 d1603 d1606 d1605 d1604
3 SA110-503 1.15 4 6 20 120 d1632 d1633 d1634 d1635
4 M67 1.34 5 10 20 120 d1689 d1690 d1691 d1692
4 SA110-503 1.60 4 10 20 120 d1771 d1772 d1773 d1774
4 PG1633+099 1.29 10 20 120 300 d1785 d1781 d1782 d1783
4 SA110-503 1.15 4 7 20 120 d1797 d1798 d1799 d1800
6 M67 1.35 5 10 20 120 d1948 d1949 d1950 d1951
6 SA110-503 1.44 4 10 20 120 d2016 d2018 d2021 d2022
6 PG1633+099 1.29 10 20 120 300 d2023 d2024 d2026 d2027
6 SA110-503 1.16 4 7 20 60 d2044 d2045 d2046 d2047
7 M67 1.33 5 10 20 120 d2092 d2093 d2094 d2095
7 SA110-503 1.64 4 7 20 120 d2145 d2148 d2147 d2146
7 SA110-503 1.15 4 7 20 120 d2169 d2170 d2171 d2172
 
Notes: Only the images used to fit the parameters of the transformation equations are shown (i.e. the images in the output from mkimsets). Airmass is an approximate average for the 4 exposures. In the actual calculations, the exact airmass for the individual images has been used. The M67 images were defocused, the PG1633+099 and SA110-503 were focused. GR, JV, JB, and JU are the 4 used passbands: Gunn r, and Johnson V, B, and U.


 
Table: Standard star observations, by field
Night Field Airmass Exposure time [sec] Image name (dfsc #)
      GR JV JB JU GR JV JB JU
1 M67 1.33 5 10 20 120 d1263 d1262 d1264 d1266
2 M67 1.34 5 10 20 120 d1388 d1389 d1390 d1391
3 M67 1.34 5 10 20 120 d1534 d1535 d1536 d1537
4 M67 1.34 5 10 20 120 d1689 d1690 d1691 d1692
6 M67 1.35 5 10 20 120 d1948 d1949 d1950 d1951
7 M67 1.33 5 10 20 120 d2092 d2093 d2094 d2095
1 PG1633+099 1.43 10 20 120 300 d1322 d1318 d1320 d1321
2 PG1633+099 1.38 7 20 120 300 d1464 d1465 d1466 d1467
3 PG1633+099 1.42 10 20 120 300 d1597 d1598 d1599 d1600
4 PG1633+099 1.29 10 20 120 300 d1785 d1781 d1782 d1783
6 PG1633+099 1.29 10 20 120 300 d2023 d2024 d2026 d2027
1 SA110-503 1.67 4 7 20 240 d1325 d1326 d1327 d1329
1 SA110-503 1.16 3 6 20 90 d1349 d1350 d1351 d1352
2 SA110-503 1.67 4 7 20 120 d1472 d1469 d1470 d1471
2 SA110-503 1.15 4 7 20 120 d1494 d1495 d1496 d1497
3 SA110-503 1.68 4 7 20 120 d1603 d1606 d1605 d1604
3 SA110-503 1.15 4 6 20 120 d1632 d1633 d1634 d1635
4 SA110-503 1.60 4 10 20 120 d1771 d1772 d1773 d1774
4 SA110-503 1.15 4 7 20 120 d1797 d1798 d1799 d1800
6 SA110-503 1.44 4 10 20 120 d2016 d2018 d2021 d2022
6 SA110-503 1.16 4 7 20 60 d2044 d2045 d2046 d2047
7 SA110-503 1.64 4 7 20 120 d2145 d2148 d2147 d2146
7 SA110-503 1.15 4 7 20 120 d2169 d2170 d2171 d2172
 
Notes: Same data as in Table [*].

The standard star images were reduced in the same way as the galaxy images, i.e. trim, bias, fat zero, dark, shutter, and flat field, with the exception, that the height of the fat zero background box (boxh) was set to 3 pixels instead of 21 pixels. This worked better for the stars close to the fat zero columns. The flat field used for the Johnson V images was a dome flat - no sky flats were taken in this filter.

next up previous contents
Next: 11.2 Aperture Photometry Up: 11. The Standard Calibration Previous: 11. The Standard Calibration

Properties of E and S0 Galaxies in the Clusters HydraI and Coma
Master's Thesis, University of Copenhagen, July 1997

Bo Milvang-Jensen (milvang@astro.ku.dk)