I’ve crunched some more precise numbers for this evening’s ISS and STS-133 passes. The times are in UTC, so you need to subtract 5 hours for Eastern Standard time. (Click here to download them in a text file.)

Ottawa-To-ISS
Time (UTCG)                Azimuth (deg)    Elevation (deg)    Range (km)
-----------------------    -------------    ---------------    -----------
9 Mar 2011 00:20:38.123              292                  0    2159.492211
9 Mar 2011 00:21:38.000              287                  4    1765.477591
9 Mar 2011 00:22:38.000              280                  9    1389.558028
9 Mar 2011 00:23:38.000              267                 15    1055.451478
9 Mar 2011 00:24:38.000              244                 22     818.373598
9 Mar 2011 00:25:38.000              209                 24     774.603489
9 Mar 2011 00:26:38.000              180                 18     951.326850
9 Mar 2011 00:27:38.000              164                 11    1258.305207
9 Mar 2011 00:28:38.000              156                  6    1622.294953
9 Mar 2011 00:29:38.000              150                  1    2011.420073
9 Mar 2011 00:29:58.922              149                  0    2150.274764

Ottawa-To-STS-133
Time (UTCG)                Azimuth (deg)    Elevation (deg)     Range (km)
-----------------------    -------------    ---------------    -----------
9 Mar 2011 00:20:05.553              292                  0    2159.008371
9 Mar 2011 00:21:05.000              287                  4    1767.294751
9 Mar 2011 00:22:05.000              280                  9    1390.441394
9 Mar 2011 00:23:05.000              268                 15    1054.707599
9 Mar 2011 00:24:05.000              244                 23     814.906252
9 Mar 2011 00:25:05.000              209                 24     768.231806
9 Mar 2011 00:26:05.000              180                 18     943.899552
9 Mar 2011 00:27:05.000              164                 11    1250.970718
9 Mar 2011 00:28:05.000              155                  6    1615.247805
9 Mar 2011 00:29:05.000              150                  1    2004.620053
9 Mar 2011 00:29:27.464              149                  0    2153.829615

Based on these numbers, the Space Shuttle Discovery (STS-133) is about 30 seconds ahead of the ISS (it rises about 30s before the ISS). For an idea of how far this is in the sky, take a look at this photo from a couple of years ago. The trail of the ISS is 30 seconds long.

Happy observing!