Hi Frank, Thanks for your detail explanation. yes i agree, it is a possibility what you said. There might have been an error in location and I got stuck with that. I did not check coordinate of the location with GPS. What I did, simply I went by the Calsky center line map. Chosen thbe location exactly on centerline, and went to that position. If you have seen the location, there was a small water stream touching a road where the center line is crossing. I have places myself exactly there. But as you have said, there might have been an error of 200/300 meters in Google map or Calsky map. THus, i have got myself located at wrong place. It is a learning for me. Now onward I shall only take the coordinate from Calsky and find the location with GPS. Thanks and regards- Debasis Sarkar , On Wed, May 28, 2014 at 10:56 PM, via Seesat-l <seesat-l_at_satobs.org> wrote: > Hello Debasis Sarkar, > > You wrote: > "despite being on centerline (Plus Minus 200 meters), I did not get ISS to > run through the center of solar disc. Instead, I had it pass through a > distance of at least 1/4 solar radii from the center of Sun." > > From your photos, I agree with your estimate: the path across the disk > appears to be about 5 minutes of arc away from the center of the Sun. Given > an altitude of 417 km, and 87 degrees high, almost straight up, this > corresponds to a position offset on the ground of about 600 meters (that's > 417km*5/3438). You say you believe your position was accurate to 200 > meters. A difference of 600 meters is only moderately outside that limit. > Is it possible you were 600 meters off the center line? Did you get your > lat/lon from some GPS-equipped device at the time of the solar transit? If > your position was instead taken from mapped data, like Google Earth or > similar, there's a possibility of an offset that large. You wondered about > an offset due to altitude above sea level. Since the ISS was nearly > straight up, there would be no significant difference. Of course a slightly > "stale" TLE is also a possibility, but there were no orbital adjustments > around the time of your transit so this seem! > s unlikely to me. Small errors in the prediction algorithms employed on > the calsky site are also a possibility. > > Frank Reed > Conanicut Island USA > _______________________________________________ > Seesat-l mailing list > http://mailman.satobs.org/mailman/listinfo/seesat-l > _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-lReceived on Wed May 28 2014 - 15:19:27 UTC
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