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                ASTERIODAL OCCULTATION - REPORT FORM

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                      EAON & IOTA-ES

              EUROPEAN ASTEROIDAL OCCULTATION NETWORK

   INTERNATIONAL OCCULTATION TIMING ASSOCIATION EUROPEAN SECTION

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1. DATE: 20 sep 2011
   STAR: TYC 2764-01038-1
   ASTEROID: (895) Helio

2. OBSERVER
   Name: Stefano SPOSETTI
   Address: 6525 GNOSCA - Switzerland
   Email: stefanosposetti@ticino.com

3. OBSERVING STATION
   Nearest city: CH-6500 Bellinzona
   Longitude: 46deg 13min 53.2sec (N)
   Latitude: 9deg 1min 26.5sec (E)
   Altitude: 260m

4. TIMING OF EVENTS
   Occultation recorded: POSITIVE
   Type of event:
   "S"tart observation;
   "I"nterrupt-start;
   "D"isappearance;
   "B"link;
   "F"lash;
   "E"nd observation;
   "I"nterrupt-end;
   "R"eappearance;
   "O"ther (specify)

   Personal Equation Substracted: No
   Event Time (UTC)       Accuracy + Comments
   code: HH:MM:SS.ss      S.ss
    -S : 18:10:05
    -D : 18:12:49.09    +- 0.09
    -R : 18:12:52.29     +- 0.09
    -E : 18:15:20
   Duration: 3.20s +- 0.18
   Mid-event time: 18:12:50.69 +- 0.09 UTC

5. TELESCOPE
   Type: Schmidt-Cassegrain, Celestron 11-inch
   Aperture: 280mm
   Focal length: 930mm (with focal reducer)
   Magnification: FOV 23x18arcmin
   Mount: Equatorial
   Motor drive: Yes

6. TIMING & RECORDING
   Timekeeping: KIWI-OSD with GPS Garmin 18 LVC
   Sensor/Camera: Videocamera WAT-120N+, CCIR, 1/2" Sony CCD-Sensor ICX419ALL
   Videocamera settings: Shutter mode=3, Gain=HI , Gamma=LO
   Device of recording: Personal computer, Imaging Source DFG/SV1 PCI, S-video,
   Virtualdub software, saved on Harddisk
   Mode of recording: Integration time=0.160s, CCIR, Huffyuv
   Time insertion: KIWI-OSD

7. OBSERVING CONDITIONS
   Atmospheric transparency: good
   Wind: no
   Star image stability: good
   Minor Planet Visible: yes

8. ADDITIONAL COMMENTS

The event with this 12.5magV star was placed just at dusk.
The telescope pointing was done about 10min before the event because of the bright sky.
Evaluation of the movie was made with Tangra.
All times were corrected accordingly to the table for 120N+ cameras made by Gerhard Dangl at:
http://www.dangl.at/ausruest/vid_tim/vid_tim1.htm

My observatory was outside the predicted path but inside the 1sigma path with 26% of a positive event probability.

The lightcurve of the event is here:
http://www.sposetti.ch/images/stories/Minor_planets/Helio_20sep2011_Sposetti.png



I could observe the event simultaneously with a Newton 40cm f/2.5 placed 3 meters apart. This second instrument was equipped with a Watec 902H Supreme video camera (0.04s integration time) and a IOTA-VTI time inserter. This setup delivered a poor signal of the faint target star but the occultation was also detected.
The resulted lightcurve is quite noisy.
The disappearance is a bit doubful. It can be evaluated at:
18:12:49.01 UTC
The reappearance is more visible. It can be evaluated at:
18:12:52.37 UTC
These times are within the error bars of the times delivered by the Watec 120N+ and KIWI-OSD setup.
The duration can be inferred as: 3.36s but, as said before, is a bit uncertain because of the poor SNR of the star in the individual frames.