Abstract

»GrazeView«: Improving Grazing Occultation Profile Predictions

Eberhard Riedel

Den Beobachtern von streifenden Sternbedeckungen bei der IOTA wird mit dem Programm »GrazeView« ein Werkzeug in die Hand gegeben, mit dem eine verbesserte Vorhersage des Mondrandprofiles durch den Beobachter selbst möglich wird.

The predictions of grazing occultations of stars by the moon generated by GRAZEREG will also in the future have the profile prediction as the well known 80-column block diagram. The new program GrazeView, first presented as a preliminary version at ESOP XVII in Belgium, was designed to overcome the problems of the old profile plots: These sometimes are less legible due to very dense plotting of lunar limb features, and are always printed only for one specific geographic position. Observers willing to see the event from quite a different location could not use the profile plot rightaway.

GrazeView is a program to be used by each IOTA observer himself. Using the grazing occultation prediction output of GRAZEREG or other programs it is possible to enter the day of the event, the chosen location (including elevation and geodetic datum) and the number of the occulted star.

The program then shows the portion of the lunar limb where the graze takes place plus the apparent stellar path along the limb features, which can be enlarged up to 8 times the normal scale. The stellar path has marks every 10 sec., so it is easier to estimate the expected time of a disappearance or reappearance of the star. Furthermore it is possible to easily move the observing site around to find the best location e.g. for multiple events. The profile consists of Watts data, as well as observed data published as MOONLIMB and ACLPPP, where available. Another feature allows the simultaneous plot of several apparent stellar paths in a chosen offset from a given location in meters or deg./min./sec. along a certain azimut direction on earth.

The screen image can be printed to a bitmap file under Windows, so an output to an ink or laser printer is possible. For that purpose the sky can be plotted white in order to save ink. Other printing features are in preparation.

The program will be distributed free among IOTA members, starting in fall 1999. The data needed by GrazeView (lunar and solar positions, lunar limb features and stellar data) is distributed on a yearly basis and can only be used for that specific year.

Dr. Eberhard Riedel, International Occultation Timing Association - European Section
Address: Schubertstr.7, 80336 München, Germany E-Mail: eriedel@compuserve.com
Telephone: +49 89 532128 Fax: +49 89 534552

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