Astrometric Reference Binaries for IRCAL

Empirically, the position angle orientation of IRCAL and the AO bench relative to the sky may vary by as much as a few degrees. Thus for precision astrometric work, it is necessary to observe binaries of known position angle in order to accurately calibrate IRCAL's orientation. At a minimum, one should generally observe at least one reference binary per observing run.

The good folks at the US Naval Observatory's Washington Double Star catalog have put together a list of canditate calibration stars, selected on the basis of having well-known orbits. In general one can not just observe any old Hipparcos binary, since Hipparcos is a single-epoch catalog and orbits are not known for most of the stars there. Even for relatively distant binaries, where orbital motion is presumably less, the fairly large uncertainties in the Hipparcos proper motions render this approach less accurate. So always choose a target from the WDS calibration targets list if at all possible!

I present here a subset of stars from the WDS calibration candidates list, selecting those most useful given IRCAL's plate scale and field of view. This list is only intended to guide you in picking out a likely star to use; once you've selected one you really ought to look it up in the WDS to get the full ephemerides and correct orbital position for the date of observations.

Here is a Lick-format target list containing these binaries. All are bright NGS objects, between 5th - 9th magnitude at V.

  WDS        Name        HD#      Grade  Reference  Equinox  Last  Ephemeris    Date     Theta   Rho   

00057+4549  STT 547AB    HD38       4    Pop1996b     2000   1994   1996-15    2001.00   182.5   5.973
00057+4549  STT 547AB    HD38       4    Kiy2001                               2001.00   182.3   6.068
02020+0246  STF 202AB    HD12446    4    Sca1983f     2000   1982   1981-90    2001.00   270.9   1.819
02442+4914  STF 296AB    HD16895    5    Hop1958      1900   1956   1960-80    2001.00   304.1  20.062
03368+0035  STF 422      HD22468    5    Hop1964b     1900   1954   1960-80    2001.00   269.8   6.672
05364+2200  STF 742      HD37013    5    Hop1973b                   1960-00    2001.00   273.8   4.093
07201+2159  STF1066AB    HD56986    5    Hop1960a     1900   1959   1960-00    2001.00   225.3   5.749
08122+1739  STF1196AB-C  HD40167    4    Hei1996b                   1996-34    2001.00    72.4   5.899
09144+5241  STF1321AB    HD79210    4    Chg1972      2000   1970              2001.00    93.3  17.185
11182+3132  STF1523AB    HD98231    1    Msn1995             1995              2001.00   268.7   1.828
12244+2535  STF1639AB    HD108007   4    Ole2000b            2000   2000-01    2001.00   324.5   1.720
14131+5520  STF1820      HD124640   5    Kiy1998             1997              2001.00   117.8   2.575
16147+3352  STF2032AB    HD146361   4    Sca1979      2000                     2001.00   236.1   7.031
17153-2636  SHJ 243AB    HD155885   4    Irw1996                               2001.00   146.0   4.850
18055+0230  STF2272AB    HD165341   1    Pbx2000b                              2001.00   146.1   3.989
18428+5938  STF2398AB    HD173739   4    Hei1987b     2000   1987   1985-35    2001.00   173.9  12.516
19121+4951  STF2486AB    HD179958   5    Hle1994      2000   1991              2001.00   206.3   7.495
20462+1554  STF2725      HD197913   5    Hop1973b     1900                     2001.00    10.8   6.078
20467+1607  STF2727      HD197963   4    Hle1994      2000   1993              2001.00   265.8   9.248
22038+6438  STF2863Aa-B  HD209790   5    Zel1965      1950   1951   1960-00    2001.00   274.5   8.233
22266-1645  SHJ 345AB    HD212697   5    Hle1994      2000   1990              2001.00     8.3   1.642

This page last updated by Marshall on 2004-10-25