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ASTEROIDAL 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: 13 Apr 2021
   STAR: UCAC4 444-070642
   ASTEROID: (1628) Strobel

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

3. OBSERVING STATION
   
   Nearest city: CH-6525 Gnosca
   Station: 143 (MPC-code)
   Longitude (DD MM SS.s): 09 01 26.5 (E)
   Latitude (DD MM SS.s): 46 13 53.2 (N)
   Altitude: 260 m
   (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 : 03:42:47
-D : 03:45:48.24 ± 0.15 s
-R : 03:45:53.34 ± 0.15 s
-E : 03:48:53

   Duration: 5.10 ± 0.21 sec 

5. TELESCOPE
   
   -Type: Newton
   -Aperture: 420 mm
   -Focal length: 1640 mm
   -Mount: Equatorial
   -Motor drive: Yes

6. TIMING & RECORDING
   
   -Camera/Sensor: Videocamera  QHY174M-GPS, SONY IMX174 CMOS sensor
   -Device of recording: personal computer, USB3 input, SharpCap PRO v. 3.2.6173.0 software, saved on SSD as SER file
   -binning = 2x2, sensor uncooled, camera bit depth = MONO16, area size in pixel = 960x600, USB traffic = 5, setted exposure = 300 ms, gain = 439, offset = 0, contrast = 0, brightness = 0, gamma = 1, banding suppression = 0, banding threshold = 35, apply flat = none, subtract dark = none
   -Timekeeping: GPS UTC clock
   -Integration time: 0.300 s
 
7. OBSERVING CONDITIONS
   
   -Atmospheric transparency: fair with some thin clouds
   -Wind: yes 
   -Star image stability: bad because of turbulence
   -Minor Planet visible during the occultation: no

8. ADDITIONAL COMMENTS
   
   Prediction:
   -Occultwatcher, IBEROC feed
   -Rank: 99
   -Probability: 47.5 %
   -Combined magnitude: 13.0 mag
   -Star magnitude: 13.1 mag V; 12.7 mag R
   -Asteroid magnitude: 15.7 mag
   -Lightdrop: 2.6 mag
   -Max duration: 5.5 s
   -Event time: 03:45:53 UT
   -Error in time: 2 s
   -Moon distance: -
   -Moon illumination: -

   Other comments:
   -Target sky position: elevation = 42 deg, azimut = 182 deg
   -About one minute before the event, the gain was lowered from 480 (maximum) to 439 because of the increasing background light of the dawn
   -At the beginning of the recording (i.e ~ 3 minutes before the event), the exposure time was setted to 200 ms. About one second before the event, the exposure was augmented to 300 ms because of the diminishing sky transparency and was keeped until the end of the recording (i.e ~ 3 minutes)
   -Tangra v. 3.7.3 was used to generate the lightcurve (aperture photometry, average background). Time reference: Start Frame 
   -A normalized lightcurve was plotted because of the changed gain and exposure time
   -D and R times were evaluated using AOTA v4.10.5.0, applied confidence level: D = 90 %, R = 90 %
   -SN at event locations: D: 6.0; R: 13.2; Ave: 9.6
   -During the event the starlight dropped to zero
   -Measured mid-event UT time: 03:45:50.8 UT
   -Many thanks to Eric Frappa for the support in the time analysis evaluation of the lightcurve
   -The normalized lightcurve can be seen here:
http://sposetti.ch/wp-content/uploads/2021/04/2021_03_24_Strobel_Gnosca.png