Below you find the announcement and some more important informations about the event:

Dear observer,

 

on Sunday morning, October 7th, the bright star Regulus will show another grazing occultation by the moon in Europe.

 

 

Between North Atlantic and Black Sea the northern limit line will cross Ireland and England between 5:32 and 5:38 UT during nautical twilight. Bright civil dawn will prevail when the graze takes place in the Netherlands around 5:41 UT. Sunrise will occur at the German border and the sun's altitude will reach 5° near the border to Poland at 5:50 UT. In Poland, Slovakia, Ukraine, Romania, and Moldavia as well as in the further progress to the Indian ocean the graze will take place in broad daylight.

 

 

For comparison, the observing conditions on May 23rd were not at all difficult, when Regulus was grazing the moon's bright rim, too. Moon and sun were both high in the afternoon sky with an elongation of 88 degrees. In a pure blue sky Regulus was easily seen in a 3 inch telescope. The following frame of my webcam recording taken with an 8" SCT gives an impression.

 

 

On October 7th the moon's altitude will be considerably high, too, but in contrast the sun will be close to the horizon, e.g. altitude will be about one degree near Hannover. At the first glance this seems to be more favourable, but the moon's elongation from the sun is only half as much compared to the previous graze. Though polarisation filters cannot really improve the contrast, but the smaller phase and therefore lower surface brighness of the moon may help to compensate instead. At a hazefree sky telescope apertures of at least three or four inches should provide good chances.

 

Interactive Google Map and Graze Data

 
Gerhard Dangl provided an interactive Google Map showing the graze line an adjustable offset line. You may choose the explanations in two versions:

English: http://www.dangl.at/maps/2007/gr071007/g071007e.htm
German: http://www.dangl.at/maps/2007/gr071007/g071007g.htm

Also included is a data table listing graze line positions, times, tan z, and position angles.

Adjustment for profile offset and elevations correction see below.

 

 Lunar Limb Profile and Offsets
 

Grazing occultations help to improve the precise knowledge about the polar limb profiles of the moon. This is necessary to evaluate Baily's bead observations during solar eclipses for the determination of the sun’s diameter. Results of the Regulus graze will be directly valuable because of a moon's libration in latitude close to zero, same as during solar eclipses. Appearance and disappearance of beads are essential events, therefore probing the depth of valleys during grazing occultations is especially important. This is easy in case of southern grazes, because rough southern limb profiles often allow maneuvering within several kilometers. But due to usually rather narrow northern limb profiles, observing stations have to be distributed within a range of only one kilometer or less perpendicularly to the limit line. Therefore maneuvering precision should not be over-stressed. As in the current case stations should be distributed across the whole strip, where graze events can be expected.

For lunar profile changes along the limit line, offset proposals can only be valid for limited distances. An animated GIF demonstrates how the profile changes across Europe. The following profile, generated with winOccult, is valid for the vincity of Hannover at about 10 degrees eastern longitude:

 

 

Graze events may occur between the graze line and about one kilometer southward. Dr. Riedel proposed a northward shift of this strip by 200 or 300 meters, but nevertheless warns not to over-interprete the precision of such predictions.

Additionally an adjustment for terrain elevation may be required. With sufficient accuracy you can calculate this parallel southward offset by multiplying the elevation of you observation site with a factor of 0.42. Both, the intended profile offset as well as the elevation correction, can be adjusted in Gerhard Dangl’s interactive Google Map.

 

Invitation for Organized IOTA/ES Observations

 

 

The northern limit line will pass about 20 km south of Hannover, where IOTA/ES will hold the yearly business meeting on the preceding day. For this reason IOTA/ES will organize an observation in that region, and cordially invites all participants as well as any other observer to join this coordinated observation.

Please see the astronomical and organizational informations for the expedition to Listringen near Hildesheim (red circle) here:

Invitation and data sheet in English

Einladung und Datenblatt in deutsch

 

Wolfgang Rothe will organize another expedition to Grossthiemig about 40 km north of Dresden (yellow circle).
For further informations please contact  w r o t h e [at] t – o n l i n e . d e

 

 
Clear skies and successful observation –

and enjoy a fine constellation which appears like this about one hour before the graze:

 

  

 

 

Alfons Gabel

 

International Occultation Timing Association / European Section

http://www.iota-es.de

For more infos, results, comments etc please contact mailto:info@iota-es.de