Grazing star occultation by the earthmoon on May 15, 2008
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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|
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
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
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|
Created with Occult 4 from Dave Herald
December 21, 2008
Questions and suggestions to => Gerhard Dangl