Occultation by asteroid (511) Davida, May 7th 2010

Dear all,

I am glad to report a positive occultation (0.21 mag drop) of the 13.2 mag star 2UCAC-332333154 by asteroid 511-Davida on May 7th,
from Ellinogermaniki Observatory Athens, Greece (see: www.asteroidoccultations.com/2010_05/0507_511_23201_MapE.gif )

http://www.astrovox.gr/forum/download.php?id=12933
The targets 30 minutes before the event

It was cloudy most of the night in Athens, as had been predicted,
but thankfully the clouds started getting out of the way 1hr before
the expected occultation time.

Light curve of the occultation

on the horizontal axis: Time (UT)
on the vertical axis: Normalized flux of the target (star & asteroid)
Reduction: Apostolos Christou

Results
Disappearance = UT 23:19:58.5 +/- 0.5 sec
Reappearance = UT 23:20:11.5 +/- 0.5 sec
Duration = 13 sec +/- 1 sec
Flux drop = 0.21 mag

Method of observation
I used a 40cm S-C telescope, CCD unfiltered images,
time source: DCF-77.
I took many short exposures (3 sec), binning 4X4, windowed frames,
read-out time ~ 1 sec, exposure rate: 1 exp. every 4 sec.
Flux drop is noticeable in 3 of the CCD frames, in accordance with the predicted time.

Regards,
Vagelis Tsamis
Sparta Astronomical Association
www.spartastronomy.gr