Grazing star occultation by the earthmoon on May 15, 2008
SAO 138778

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On May 15, 2008 at about 21:08 UT the moon grazed the star SAO 138778 in a height of 31 degrees over the southwest horizon with the dark area of the north pole. Thereby the star were occulted and became visible several times by the moon mountaines and moon valleys on the moon horizon. Because of moving clouds two of five occultations could not be recorded direct on video.


The earthmoon grazes the star SAO 138778
The earthmoon grazes the star SAO 138778
Diagram created with Guide 8 from Bill J Gray


The moon profil at the calculated graze point
The moon profil at graze point
Diagram created with Occult 4 from Dave Herald

This grazing star occultation on the dark moon area was captured with my equipment with a relative high accuracy of some milliseconds and evaluated later.

Diagram of equipmennt setup
Diagram of equipmennt setup


The path of the grazing star occultation runs cross through Europe
Occultation path in Europe


The calculation of the observation point was done in a self made table sheet
Calculation of the observation point


Position elevation and moon profil require a double parallel shifting of the observation point (OP)
Observation point northeast from Fromberg
Correction of observation point = (- 716m) + (-1694m) = -2410m shift to the green line for 0m above sea level


Aerial image of the calculated observation place northeast from Fromberg - in northern Woodquarter
Observation place northeast from Fromberg
Observation position 48° 44´ 34.0" North, 15° 05´ 49.4" East


The observation place could be chosen direct on a way fork in the calculation
Observation place northeast from Fromberg


Moving clouds prevented the time capturing on two of ten events
Observation place northeast from Fromberg


The Newton telescope for observing and timing with video and GPS
Observation place northeast from Fromberg



Observation report

Date Observer Position - 3932 Fromberg Observer 2008/05/15 48° 44´ 34.0" North (WGS84) Gerhard Dangl Star 15° 05´ 49.4" East (WGS84) 3830, Nonndorf 12 SAO 138778, +8.3mag 545m (MSL), 589m (WGS84) AUSTRIA
TELESCOPE: Type: Newton Focal length: 1200mm Aperture: 254 mm Magnification: video/primary focus/FOV 16.5'x13.7' (640x576, 1.56"x1.43" per pixel) Mount: Equatorial EQ6 with EQMOD Motor drive: Yes TIMING & RECORDING: Timekeeping: GPS 1PPS Garmin18 LVC + KIWI-OSD Sensor/Camera: WAT-902H2 Ultimate, CCIR, 1/2" Sony CCD-Sensor ICX419ALL Mode of recording: It=20ms (50 Img/s), Video CCIR, AVI, YUY2, Huffyuv, Device of recording: Xpert V-Stream Videograbber USB2.0, Notebook Harddisk Time insertion: KIWI-OSD OBSERVING CONDITIONS: Atmospheric transparency: poor Wind: 0.5 - 1.0 m/s Star image stability: fair Temperature: 276 Kelvin (+03 deg Celsius) ADDITIONAL COMMENTS: Predictions with Occult4 Video evaluation accomblished with VirtualDub1.8.5 Only clear glass filter (Astronomik) for CCD protection was used 3-D position and timing with Garmin GPS18 LVC receiving 09 satellites Horizontal dilution of precision 1.0, geoidal separation 44.5m Position shift calculations: Correction for MSL 545m: - 716 meters (path calculated for Mean Sea Level=0m) Correction for profile : -1694 meters Observation point (OP) : -2410 meters

Table with precalculations prepared with Occult 4 from Dave Herald
Grazing Occultations near Nonndorf_0m_25cm, Austria
E. Longitude   15 14  8.4,  Latitude  48 47 13.5,  Alt.    0m;  Telescope dia 25cm;  dMag 0.0

       day  Time   P   Star  Sp  Mag  Mag    % Elon Sun Moon      Cusp angle   Distance       Azimuth    Path formula
 y   m  d  h  m  s      No  D     v    r V  ill     Alt Alt               o          km 
08 May 15 21  9 53 Gr 138778 F8  8.3  8.0   84+ 133     31 ** GRAZE: CA 16.9N; Dist.  9km in az. 240deg. [Lat =48.62-1.12(E.Long-15.24)]

Table with results of the video measurement

Phenomen       Cause       hh:mm:ss.sss   Comment
Video start                21:05:04.557   First video frame
Cs             cloud       21:08:14.635   Clouds start, star invisible
Ce             cloud       21:08:24.634   Clouds end
R1             moon limb   21:08:34.754
D2             moon limb   21:08:36.234
R2             moon limb   21:08:36.274
D3             moon limb   21:08:36.394
R3             moon limb   21:08:36.434
Cs             cloud       21:08:41.954   Clouds start
Ce             cloud       21:09:18.194   Clouds end
R4             moon limb   21:10:10.833
D5             moon limb   21:10:20.473
R5             moon limb   21:10:22.073
Cs             cloud       21:10:30.993   Clouds start, star invisible 
Ce             cloud       21:10:40.873   Clouds end, star visible
Cs             cloud       21:11:31.912   Clouds start, star invisible 
Ce             cloud       21:13:54.310   Clouds end, star visible
Video end                  21:14:17.349   Last video frame

Because of the moving clouds a low signal/noise ratio exists in the records. Therefor the evaluation of the videos was not operated automatically with Limovie but manually with VirtualDub in single frame modus.

Video R1, D2/R2, D3/R3
Video 1 - MPEG4 1.7MB
Video R4
Video  2 - MPEG4 1.1MB
Video D5/R5
Video  3 - MPEG4 1.4MB

A report with data of this measurements was created with Occult4 and transfered via email to the relevant autority for further use.


The reduction of the measurement data to the moon profil
Reduction of the measurement data
Created with Occult 4 from Dave Herald

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December 21, 2008
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