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 Diagram created with Guide 8 from Bill J Gray

The moon profil at the calculated 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

The path of the grazing star occultation runs cross through Europe

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

Position elevation and moon profil require a double parallel shifting of the observation point (OP) 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 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

Moving clouds prevented the time capturing on two of ten events

The Newton telescope for observing and timing with video and GPS

 

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