Thank you, Tony. I did not realize the shadow constraint. Having used HA, I know the sky charts resolve the transit path for a location based on the ISS first rising above the local horizon and terminate with the ISS entering shadow. In retrospect, TheSky and Satellite Tracker do not discern visibility along a transit path, only report "if" the ISS is visible. Adam If you use HA to select the ISS from the select a satellite option, and ask for all passes in the 10 day interval that includes sunday may 18 for your location , you will see that their is a pass culminating at 21:35 EDT or may 19, 01:35 UT. Its just that HA reckons its in shadow. The other software programmes you used obviously disagreed. Its hard to calculate a satellite illumination accurately when the trajectory is nearly tangent to the shadow cone. Differences in the effective shadowing radius of the Earth that is assumed can result in differing results from different programmes. I remember doing some observations utilizing Echo 1 (1960 9A) or Echo2 ( 1964 4A ) at the request of Moonwatch HQ to help decide the right number empirically. Tony Beresford ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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