5919 Obs 2007-03-11 problems

From: ComHem (b.gimle@comhem.se)
Date: Mon Mar 12 2007 - 05:35:39 EDT

  • Next message: Brad Young: "PPAS BY Early March 2007"

    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
    



    This archive was generated by hypermail 2b29 : Mon Mar 12 2007 - 05:48:58 EDT