Coming home very late after baby-sitting a granddaughter I found the sky very clear (2nd night in months!) and just about time to locate USA 184 near delta Leonis with the telescope. Though it was the first time I saw it, I found it easy, bright and steady, and easy star pairs. After ~3 min observations I went in to make notes, and expected no problems. However, I could not recognize the stars I had used, neither in SkyMap nor in ObsReduce (problem 1)! IOD format: 29249 06 027A 5919 E 20070311003608030 17 25 1116064+211813 97 S (29249 06 027A 5919 E 20070311003701960 38 25 1117385+204511 78 S) 29249 06 027A 5919 E 20070311003727860 17 25 1118031+202602 28 S (29249 06 027A 5919 E 20070311003851160 17 25 1119941+190555 97 S+080 04) I used Mike's integrated elset: USA 148 int2 1 29249U 06027A 07068.58010703 0.00000495 00000-0 00000+0 0 06 2 29249 63.3401 11.9691 7202455 269.5129 0.0000 2.00645648 06 00:36:08 was 80% outside right (left?!) of .3 deg pair - sat was 1.7 s early? 00:37:02 was an inaccurate appulse .8 deg from delta Leo - I thought it was taken late, and timing does not invalidate previous and next obs. 00:37:28 was merely 1/20 to the right of the upper of two along the track - 1.9 s early? 00:38:51 was 1/6 to the left of the upper of two along the track - but this position makes the sat 28.6 s early, so these star IDs are clearly wrong ! ... Cross-track errors for these are .03 (.04) .05 (and .06) deg, according to ObsReduce. Problem 2: Some stars used for these splits/right angles are mag. +10 - I believe that is close to my limit with 8" at only 27x power (32 mm eyepiece and f/4), but subjectively they were easy. Problem 3: I added the first three obs, and the predicted position for time 4, to SkyMap's DEEPSKY.TXT file. They show a track with a lower inclination and angular speed. Problem 4: In SkyMap I see a better star pair for the third position, with a +10.50 mag star at 11:17:44.39 +20:32:56 I have the Tycho105 star file on my new PC, since Tycho120.zip (or TychoAll) are missing at http://www.satobs.org/programs/ObsReduce/ Using that star in SkyMap, and the same time offset at first obs, I find there is a better star pair; the sat WAS left as my notes said. Adding that star to ObsReduce's addstar.txt, and using the better star pair for first obs I get three new pos. 29249 06 027A 5919 E 20070311003608030 37 25 1116151+212683 57 S (29249 06 027A 5919 E 20070311003701960 18 25 1117266+204985 78 S) 29249 06 027A 5919 E 20070311003727860 17 25 1117716+203267 97 S but the fourth is still missing. Time offsets reported are +8.2, (+7.2) +8.5 s late, Xtrack .05 (.05) .04 deg, now all east of the predicted track. Problem 5: In SkyMap I see a pair where the sat would be at the fourth pos, but mag are +10.58 and +11.07, and the sat would be 1/6 left on extended line, not at right angles. If my notes were correct, I would have to to use the +7.91 star 0.5 degrees down (possibly a +10.75 star 0.3 deg down west) but these alternatives increase the cross-track error, and all differ in time offset from the first three obs. (29249 06 027A 5919 E 20070311003851160 17 25 1119421+193501 37 S) -- Björn Gimle -- -- COSPAR 5918 WGS84, +18.10127 (E), +59.29813 (N), 44 m -- -- COSPAR 5919, MALMA, +18.6206 (E), +59.2615 (N), 33 m -- -- COSPAR 5920, FRUVIK,+18.4820 (E), +59.3260 (N), 11 m -- ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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