2009-08-03: 45 Cap occultation (immersion) by Jupiter



DATE:                         2009-08-03
STAR:                         45 Cap (5.96m) 
PLANETARY BODY:    Planet Jupiter

    Name:    Marc DELCROIX
    E-mail: delcroix.marc@free.fr
    Address: 2, rue de l'Ardèche 31170 TOURNEFEUILLE, FRANCE

OBSERVING STATION: Nearest city: Tournefeuille (31 - France)
  Station:    Marc Delcroix's Home
  Latitude:   N 43 34 59.05 (Google Earth)
  Longitude: E 01 19 34.43 (Google Earth)
  Altitude:    163 m (Google Earth)

  Single station

  Type of event
  Start observation   Interrupt-start   Disappearance   Blink   Flash
  End observation     Jnterrupt-end     Reappearance    Other (specify)

  Event   Time (UT)    P.E.   Acc.  
  Code   HH MM SS.ss   S.ss   S.ss
    S  - 22:50:01.3217      0.008  :
   "H" - 22:59:04.8           0.1    : Half nominal stellar intensity
    E  -  23:04:04.8726     0.008  :

    Type:      REFLECTOR    Aperture: 254 mm   Magnification: F/11
    Mount:    EQUATORIAL   Motor drive: YES

  Time source: NTP server ntp2.oma.be, synchronisation with BeeperSync running
  Sensor: CCD (Lumenera SKYnyx 2-0M, 0.4s individual exposures, Custom Scientific 890nm(18nm) methane filter)
  Recording: PC (Lucam Recorder)

  Atmospheric transparency:     4/5      Wind: none         Temperature: ~22°C
  Star image stability:               4/10    Minor planet visible: yes

Observer analysis results:

- half nominal stellar intensity estimated at 22:59:05.8 UTC, computed around 22:58:42 UTC, C-O=-24s
        computed time derived from
            -estimated predicted time for star at 1bar level in Jupiter atmosphere for observing location between Pic du Midi and Paris (France) - see http://jupiter2009.iota-es.de
            -estimated predicted time for half nominal stellar intensity (at 2µbar level in Jupiter atmosphere) = time at 1bar level -36s


Click here to see animation of 2 minutes individual exposures around estimated half nominal stellar intensity time

Click here to see animation of 3 images over the total recording 14 minutes (magnified by 2, not for photometry purpose)


6 minutes light curve around half nominal stellar intensity:


2 minutes light curve around half nominal stellar intensity:



- 2000 0.4s frames, from 22:50:01.3217 UTC to 23:04:04.8726 UTC
- PC time synchronized with Beeper Sync, estimated time keeping precision below 8ms

Data processing information:

- Individual frames timestamp at mid of individual exposure, taking into account delay between end of frame and time of recording on PC as delay between current and previous frame minus individual exposure time

- Dark substraction
- Exposures aligned
- Photometry performed:
    - with fixed circle including star and part of Jupiter limb (where immersion occured), excluding major Jupiter details in methan (Great Red Spot) rotating along capture
    - on Io satellite with same radius circle

- Intensity calibration:
    - usage of factor=average Io Intensity/Current frame Io intensity for each frame to compensate for turbulence/transparency
    - substraction of linear (y=ax+b) least squared regression performed on intensity before start of occultation, to compensate for sky background evolution

- Half nominal stellar intensity estimation performed on 19 frames sliding average:
    - by calculating half nominal stellar intensity as [(calibrated intensity averaged before immersion)+(calibrated intensity averaged after immersion)]/2
find the time for which this intensity is reached on the main decreasing light curve (between 22:58:48 UTC and 22:59:13 UTC)

    - Method 1: intersection of light curve with line average of linear least squared regression of intensity before immersion, and wh

Marc Delcroix
2009-08-07, updated 2009-08-09


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