Op 17-8-2011 13:49, alain.figer@club-internet.fr schreef: > Hi Marco, > > Last night I took a series of 6 consecutive photos in a field in Aquila. All > photos were of 4 sec duration. > > In all the photos, a same flashpattern seems rather obvious : 1 bright maximum > followed by 2 secondary maxima. At times both secondary maxima merge together. > The brightest flash is very sharp and also variable in magnitude. It can be at > times definitely fainter. I derived a photometric period of 0.73 sec, > respectively : 0.727 ; 0.729 ; 0.728 ; 0.723 for the 4 photos with a complete > 4-sec track. Hi Alain, Those are cool images! And you are so right in the periods you derive! Going back to my data (see http://www.satobs.org/seesat/Aug-2011/0088.html), I get a result *exactly* like yours...! With only two exceptions (where secondary peaks are missing/not pronounced), if I take each third peak in the sequence, I get a period of 0.73 +- 0.03 seconds, exactly what you found. The two exceptions (marked * in below table) , themselves are intervals close to this: 0.77 and 0.68 seconds. This suggest two submaxima are missing inbetween two major peaks in these cases. table: peak nr ; seconds after 20:51:00 UTC ; interval between these peaks (s). -------------------------------------- > 3 18.15 0.76 > 5 18.9 0.75 > 7 19.63 0.73 > 8 20.4 0.77 * > 10 21.14 0.74 > 12 21.88 0.74 > 14 22.62 0.74 > 16 23.32 0.70 > 18 24.06 0.74 > 20 24.81 0.75 > 21 25.49 0.68 * > 23 26.22 0.73 > 25 26.91 0.69 --------------------------------------- secondary maxima tend to have intervals of about 0.27s and 0.46s, (see the full list of intervals here: http://www.satobs.org/seesat/Aug-2011/0088.html),in that stereotype order: so a "main" peak in the 0.73 cycle, followed by a 0.27s separated peak, followed by a 0.46s separated peak (the both together creating the 0.73s cycle). Neat! In June, it became very apparent from my photographs that the "regularity" of the flash pattern is, as it is dependant on the exact viewing angle, changing over the course of a pass: http://sattrackcam.blogspot.com/2011/06/nanosail-d-evolution-of-flash-pattern.html Early June, a very regular longer period was gradually added upon by smaller secondary peaks, creating a seemingly more chaotic pattern - see the URL above. I guess the results of this mid-august show something similar: a main longer periodicity "hidden" because of smaller subperiodicities on it. Your images show the sequence perfectly though! - Marco ----- Dr Marco Langbroek - SatTrackCam Leiden, the Netherlands. e-mail: sattrackcam@wanadoo.nl Cospar 4353 (Leiden): 52.15412 N, 4.49081 E (WGS84), +0 m ASL Cospar 4354 (De Wilck): 52.11685 N, 4.56016 E (WGS84), -2 m ASL SatTrackCam: http://home.wanadoo.nl/marco.langbroek/satcam.html Station (b)log: http://sattrackcam.blogspot.com ----- _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-l
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