Obs 24 Jan 2006 Part 2 last

From: Greg Roberts (grr@iafrica.com)
Date: Thu Jan 26 2006 - 11:32:45 EST

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    Observations 24 Jan 2006:(Part 2)
    ----------------------------------
    
    Cosatrak 1 (Computerised satellite Tracking System).
    MINTRON low light level CCD surveillance camera (0.005 lux typical
    in non integration mode) and 0.00005 lux in STARLIGHT mode with 128
    frame integration.
    
    Used with 145mm focal length f/2.5 lens,integrating for 128 frames
    which is equivalent to an exposure of 2.56 seconds per image.
    
    Site 0433 : Longitude 18.51294 deg East, Latitude  33.94058 deg S,
    Elevation 10 metres - situated in Pinelands (Cape Town), South Africa
    
    
    Stray seen:
    -------------
    
    Ariane 3 rocket body  range 31050 kms, magnitude variable
    15562 85 015C   0433 G 20060124211437400 56 15 1010258+092728 39  +105 05
    Cosmos 1704  magnitude variable
    16291 85 110A   0433 G 20060124184544600 56 15 0518021+154418 39  +070 05
    Ariane 5 rocket body  range 8100 kms, magnitude variable
    27716 03 013C   0433 G 20060124191454000 56 15 0540142+290251 39  +080 05
    SL6-rocket body   range 5330 kms, magnitude variable
    15223 84 089D   0433 G 20060124204103200 56 15 1102317-072226 39  +090 05
    Intelsat 904
    27380 02 007A   0433 G 20060124204758100 56 15 0924469+052005 39  +100 05
    SL-12 rocket body  range 38160 kms
    15581 85 016F   0433 G 20060124211211800 56 15 0642495+191503 39  +110 05
    15581 85 016F   0433 G 20060124214818000 56 15 0719514+193418 39  +105 05
    SL-12 rocket body  range 37730 kms
    15630 85 024D   0433 G 20060124211211800 56 15 0643502+193311 39  +110 05
    15630 85 024D   0433 G 20060124214818000 56 15 0721353+194051 39  +110 05
    Globalstar M046
    25651 99 012C   0433 G 20060124212301500 56 15 0010550-581631 39  +070 05
    SL-12 rocket body
    19120 88 039B   0433 G 20060124212414700 56 15 0008059-571906 39  +041 05
    OPS 8579 (DMSP) magnitude variable
    07218 74 015A   0433 G 20060124212338900 56 15 0010551-582150 39  +080 05
    Raduga 18
    16497 86 007A   0433 G 20060124214512700 56 15 0701582+185535 39  +115 05
    SL-12 rocket body range 37730 kms
    18578 87 096D   0433 G 20060124215624800 56 15 0728224+173255 39  +110 05
    SL-12 rocket body range 37840 kms
    18446 87 091D   0433 G 20060124215624800 56 15 0730030+174535 39  +110 05
    Atlas 5 centaur  range 36300 kms
    27500 02 038B   0433 G 20060124215624800 56 15 0732229+181838 39  +105 05
    
    
    Notes:
    --------
    (1) Period of #90029 (reported yesterday) about 71 seconds from
        invisible ( ie fainter than mag 12) to about +7
    
    (2) Period of #90041 (reported yesterday) is a bit complex. I can
        see it slowly brightening from invisibilty (fainter than mag +12)
        and then it gives a flash followed a few seconds later by another
        flash and then invisible and it repeats the cycle. The two flashes
        are not of equal magnitude, nor are successive pairs the same
        magnitude. Sometimes the interval between the double flashes is as
        much as 18 seconds. The approximate interval between the main
        flashes is just over a minute ( 64 seconds?). I also got the
        impression that as time passed the flashes were getting brighter.
    
    (3) Looks like I stumbled upon the graveyard for SL-12 rocket bodies-
        found 4 close together at dec +17 to dec +18 :-))
    
    (4) This concludes observations for 24 Jan - now going to play with
        ASTROSNAP in producing good dark frames and flat fields. Once I
        have this solved properly I can probably increase my magnitude
        penetration by another magnitude.
    
        For the uniniated dark frames are exposures made with no light
        reaching the CCD chip and thus one gets a record of the dead
        pixels which show up as bright dots and can be mistaken as 
        geostationary satellites.
    
        In addition it also reveals the glow on the left side of the image
        frame caused by an amplifier in the CCD circuitry. The dark frame
        obtained is then subtracted from an actual exposure and
        theoretically the dead pixels and amplifier glow should then be
        removed from the image ( so says theory!!) but Im not getting it
        exactly right at the moment so some experimentation is needed,
        especially as I have over 200 dead pixels in my ccd chip and they
        all look like stars (or geostationary satellites!). Unfortunately
        the number of dead pixels are growing as cosmic rays strike the
        CCD pixels (diodes) and "pop" them. This happens even with the
        camera off so eventually I will have so many dead pixels that
        the camera becomes useless for this kind of work.The CCD chip
        has about 437664 pixels so currently about 0.05% are dead.
    
        A flat field is an image made of the twilight sky with nothing in
        the field of view. This shows up blemishes like dust on the ccd
        chip or nearby lens surfaces as well as defects like vignetting
        ( non uniform field illumination) etc. So once flat fields and
        dark fields are applied to the image one should be left with a
        "perfect" image.... (and so say all of us!)
    
    
    (5) This endeth the lecture for today:-))
    
    Cheers
    Greg
    
        
    
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