27 June 1995 This is a more-or-less verbatim copy of something I wrote following my 22 June run. Here are some references I found useful for Thuan-Gunn filter photometric standard stars to use with DIS in imaging mode: (0) Thuan and Gunn 1976 PASP 88:543 defines the system. The standards fainter than g ~ 10.5 don't saturate the chip in a 1 second exposure (though this is seeing dependent); there are about 12 such stars. Positions are given to accuracy to 0.1 m RA and 1 min dec; not sure how many of the stars have large proper motions that would need to be accounted for-- I used BD+28 4211 and BD+17 4708, which did turn up where expected. (i) Inger Jorgensen, 1994, PASP 106:967-973, "Secondary Photometric Standards for the Thuan-Gunn and Johnson-Kron-Cousins Systems" Table of some 100 standard star magnitudes, without coordinates. Therefore, one has to find coordinates in earlier literature cited by Jorgensen: (ii) Stobie et al, 1985, A&A Supp, 60:503-515, "CCD stellar sequences in galactic structure fields", has coordinates for two standard star fields, F762-9 and F1038-6, with photometry in Jorgensen. The one I used, F1038-6, is at 23:31:06 +09:51:00 (1950.0) ; the other is at 3:30:49 -06:15:30 (1950.0). Each has 8-9 secondary photometric standard stars in one DIS field, with a wide range of magnitudes; 5 seconds didn't saturate the brightest star (r=12.7) in F1038-6 but 20 sec did; haven't yet looked to see if I saw the faintest (r=19.2). (iii) Four further fields in Jorgensen's table have coordinates in Landolt 1992, AJ 104:340. They are PG1633+099, at 16:35:32 +09:47:10 (2000.0) [4 stars, r mag 12.7-15] ; Mark A at 20:43:58 -10:46:30 (2000.0) [4 stars, r mag 13.6-15.8]; SA 92 at 00:54:41 +00:42 (2000.0) [6 stars, may not quite fit in 1 DIS field, r mag 13.0-15], and SA 110 at 18:43:09 +00:30:15 (2000.0) [8 stars, r mag 11.4-13.8]. I used the latter, found 5 sec saturated some stars in g, 1 sec did not, and 2 sec would probably saturate in good seeing. (iv) Kent's paper 1985 PASP 97:165-174 has much photometry but seems not to tabulate coordinates beyond the original Thuan-Gunn standards. Might be a useful place to continue the lit search. That's it for now. Please feel free to pass these along to anyone else who might be interested; I've tried to be careful with the above coordinates but can't absolutely guarantee no errors. James Rhoads (rhoads@astro.princeton.edu). APO APO APO APO APO Apache Point Observatory 3.5m APO APO APO APO APO This is message 1 in the apo35-dis archive. You can find APO the archive in /u/strauss/apo/mailer/apo35-dis on astro.princeton.edu APO To join/leave the list, send mail to apo35-request@astro.princeton.edu APO To post a message, mail it to apo35-dis@astro.princeton.edu APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO