Grazing star occultation by the Earthmoon on October 21, 2008
SAO 79660

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On October 21, 2008 at about 04h24 UTC the Earthmoon grazed the star SAO 79660 in a height of 31 degrees above the southwest horizon with the dark area of the moon southpol. Thereby the star was occulted and became visible several times by the moon mountaines and moon valleys on the moon horizon. It is remarkable that despite of very dense ground fog ten occultation events could be recorded on video due to the use of an infrared pass filter.


The earthmoon grazes the star SAO 79660
The earthmoon grazes the star SAO 79660
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 southwest from Schirnes
Correction of observation point = (-224m) + (-2026m) = -2250m shift to the green line for 0m above sea level


Aerial image of the calculated observation place southwestt from Schirnes - in northern Woodquarter
Observation place southwestt from Schirnes
Observation position 48° 51´ 05.9" North, 15° 15´ 08.3" East


The observation place and all the region around was covered by dense ground fog
Observation place southwest from Schirnes

When I started to drive to the observation place dense ground fog was around. After arriving at the observation place I could see that the fog was more dense there. No star was visible through the ground fog. Also not the bright Sirius with -1mag. Only the moon was visible but dimmed and with a halo around due to the waft of mist. But I had done all the preparation work for this observation until this moment so I decided to setup my station just to get a confirmation that this observation was impossible through the dense fog.

But because of the use of an Astronomik Planet IR Pro 807 filter and the high IR sensitivity of the WAT-902H2 Ultimate camera the star SAO 79660 with +7.6mag really could be hold visible on the bright and outshined moon limb. A short change to the filters RG850 and RG1000 made the result more worse. Then with the Astronomik Planet IR Pro 807 filter ten events of this grazing star occultation could be recorded.

The visibility on the ground was only few meters also in the light of the lamp
Observation place southwest from Schirnes


Observation report

Date Observer Position - 3842 Schirnes Observer 2008/10/21 48° 51´ 05.9" North (WGS84) Gerhard Dangl Star 15° 15´ 08.3" East (WGS84) 3830, Nonndorf 12 SAO 79660, +7.6mag 521m (MSL), 565m (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: very bad (dense ground fog) Wind: No Star image stability: fair Temperature: 276 Kelvin (+03 deg Celsius) ADDITIONAL COMMENTS: Predictions with Occult4 WAT-902H2 Ultimate with Astronomik Planet IR Pro 807 Filter and manual cable gain control. 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 10 satellites Horizontal dilution of precision 1.1, geoidal separation 44.5m Position shift calculations: Correction for MSL 517m: - 224 meters (path calculated for Mean Sea Level=0m) Correction for profile : -2026 meters Observation point (OP) : -2250 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 Oct 21  4 25  7 Gr  79660 K0  7.6  6.8   53-  94 -11 63 ** GRAZE: CA  9.9S; Dist.  9km in az.  20deg. [Lat =48.88-0.25(E.Long-15.24)]

Table with results of the video measurement

Phenomen       Cause       hh:mm:ss.sss   Comment
Video start                04:19:09.539   First video frame

D1             moon limb   04:24:53.335   (+/- 20ms)
R1             moon limb   04:25:05.734   (+/- 20ms)

D2             moon limb   04:25:07.334   (+/- 20ms)
R2             moon limb   04:25:15.214   (+/- 20ms)

D3             moon limb   04:25:15.654   (+/- 20ms)
R3             moon limb   04:25:15.774   (+/- 20ms)

D4             moon limb   04:25:24.014   (+/- 20ms)
R4             moon limb   04:25:26.134   (+/- 20ms)

D5             moon limb   04:25:57.054   (+/- 80ms)
R5             moon limb   04:26:51.933   (+/- 20ms)

Video end                  04:30:05.171   Last video frame

Because of the dense waft of mist 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 D1
Video D1 - MPEG4 1.2MB
Video R1, D2
Video R1, D2 - MPEG4 1.76MB
MPEG4 1.76MB
Video R2, D3/R3
Video R2, D3/R3 - MPEG4 1.2MB
Video D4/R4
Video D4/R4 - MPEG4 1.8MB
Video D5
Video D5 - MPEG4 920kB
MPEG4 920kB
Video R5
Video  R5 - MPEG4 900kB
MPEG4 900kB

A report with data of this measurements was created with Occult4 and transfered via email to the relevant autority in Japan for evaluation and 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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January 26, 2009
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