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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: 14 Mar 2018
   STAR: 4UC 574-016894
   ASTEROID: (4000) Hipparchus

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

3. OBSERVING STATION
   Nearest city: CH-6525 Gnosca
   Longitude: 9d 1m 26.5s (E)
   Latitude: 46d 13m 53.2s (N)
   Altitude: 260m
   (WGS84)

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: -
   Event Time (UTC) Accuracy + Comments
   code: HH:MM:SS.ss S.sss

-S : 19:52:53
-D : 19:57:34.80 ± 0.160 s
-R : 19:57:35.44 ± 0.160 s
-E : 20:01:06

   Duration: 0.640 s ± 0.320 s

5. TELESCOPE
   -Type: Schmidt-Cassegrain, Celestron 11-inch
   -Aperture: 280 mm
   -Focal length: 930 mm (with focal reducer)
   -Magnification: FOV 23x18 arcmin
   -Mount: Equatorial
   -Motor drive: Yes

6. TIMING & RECORDING
   -Sensor/Camera: Videocamera WAT-910HX-RC, CCIR, 1/2", ICX429ALL sensor
   -Videocamera settings: Shutter = x16; Gain = 41/41; Gamma = 1.00
   -Device of recording: Personal computer, Imaging Source DFG/SV1 PCI, composite input, Virtualdub acquiring software, saved on Harddisk as Huffyuv compressed file
   -Timekeeping: GPS 1PPS (US Global Sat EM-406A)
   -Time insertion device: IOTA-VTI, v.1.1.42
   -Integration time: 0.320 s
  
7. OBSERVING CONDITIONS
   -Atmospheric transparency: good
   -Wind: none 
   -Star image stability: fair
   -Minor Planet Visible during the occultation: no

8. ADDITIONAL COMMENTS
   -Target position: elevation = 54 deg; azimut = 246 deg.
   
   Accordingly to Occultwatcher prediction, IBEROC feed:
   -Rank: 18
   -Probability: 10.5 %
   -Combined magnitude: 13.7 mag
   -Star magnitude: 13.7 mag
   -Asteroid magnitude: 17.4 mag
   -Lightdrop: 3.3 mag
   -Max duration: 1 s
   -Event time: 19:57:38 UT
   -Error in time: 4 s
   -Moon distance: below horizon
   -Moon illumination: -

-A visual inspection of the individual frames shows that the event lasted 2 integration intervals.

-Tangra v. 3.6.15 was used to generate the lightcurve (aperture photometry, average background).

-From the lightcurve a csv-file was generated. That file was opened in a excel sheet.

-The light intensity (signal minus background) averaged on 320 frames (i.e. 40 integration intervals) of the pre-Disappearing phase is 1365 ADU, st. dev. 369 ADU. 
The light intensity averaged again on 320 frames of the post-Reappearing phase is 1396 ADU, st. dev. 311 ADU.
The light curve drops to 275 ADU of the first integration interval during the occultation event and is followed by the 443 ADU intensity of the second integration interval.
So the light intensity in the occultation time period was not zero, as one would expect from a predicted lightdrop of 3.3 mag.
These numbers show that the occultation lasted probably less than 2 integration intervals, i.e. less than 0.640 s.

-A correction of - 0.180 s was applied because of the use of an integration camera.

-A lightcurve can be seen here:
http://sposetti.ch/wp-content/uploads/2018/03/20180314_Hipparchus_Sposetti_2.png