Evening all I forwarded some of the SeeSat reports about the program HEAVENSAT to its author and queried whether a bug or not. I attach his reply just received which clarifies operation of his program. Hope this helps. Cheers Greg ----- Original Message ----- From: "HeavenSat" <HeavenSat@mail.ru> To: "Greg Roberts" <grr@telkomsa.net> Sent: Tuesday, October 31, 2006 8:23 PM Subject: Re: Bug? > Hi! > >>>It has come to my attention that among the programs being used for >>>predictions, there are some significantly differing results for >>>at least some objects. A specific case is ETS 6 (94-56A, 23230). >>>Orbitron and Heavensat gave predictions that were something like >>>one hour of RA different from what Highfly predicted... > > I will take a little time for me to examine the problem. > >>I have installed and tested Heavensat and I believe that its >>computations are correct, but I found that one of its displays >>could be misleading. >>In particular, I tested a case where ETS 6 was low in my south >>rising towards apogee: >>30.3N 97.8W BCRC 2006 Oct 28 Times are UT 23230 ETS 6 94 56A >>Hrs Min Alt Azi Hgt Range R A Dec (2000) >>2 0 27.8 152.6 9643 11298 23 41.36 -26.48 >>2 10 26.6 148.0 10447 12190 0 10.02 -25.53 >>The SeeSat program and Ted's ObsReduce produced very similar answers. >>When I ran Heavensat and asked it to find a passage near a star >>during this 20 minute interval, it produced a prediction that the >>satellite would pass about 1/10 of a degree from the star SAO 192166 >>at 02:00:51. The altitude was 27.5 and the azimuth was 152.0. >>When I changed the field of view to 2 degrees, the mag 6 star was >>just above the plotted satellite trajectory. >>When I ran Heavensat in the "passes prediction" mode, the output >>was the entire 14 hours that ETS 6 was above my horizon (even though >>the duration was set to 20 minutes). The [***] was around the maximum >>altitude of the pass - alt 62, azi 153, time 12:22. So this was 10 >>hours after the 20 minute "duration" of the prediction. I could >>zoom in on the 02:00 part of the trajectory and the alt/azi was >>correct, but the 6th magnitude star did not appear. It seems that >>the stars are in their proper places for 12:22 UT, not 02:00 UT. >>There are no RA and Dec labels on this display. This is confusing. >>So I can see how you could select a part of the trajectory that >>was one or more hours off of the time of prediction and the stars >>would not be in the right place for that part of the trajectory. > > Shortly - there is no bug. > > I will try to explain: > The logic of mode "passes prediction" is to give prediction of > satellite pass for whole trajectory from rise to set if duration > interval > lays in borders or intersects of full pass time. After passes > prediction, program always shows satellite in its maximum altitude > and draws stars of course for the > same time. Satellite trajectory cannot be selected, it is just shows > related information. So it is normal when Mike not saw the wanted > star in the position for 02:00:51 part of track. This star was at place > at time of satellite maximum altitude (12:22). All objects in program > are always drawn at the time which displays on left-top HUD or > right-bottom status field. > To avoid this confusion I will add a function on the right click on > track to set corresponding time, but now I only may recommend to > change time for the sky. > > > Best regards, > Aleks ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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