[vsnet-campaign-deltavel 26] November 21st eclipse of delta Velorum

[Sebasti若n Otero <varsao@fullzero.com.ar>]

Dear observers:

The first record of a delta Velorum eclipse is the Galileo event of November
21st, 1989.
Exactly 11 years later we will witness another November 21 event.

According to our ephemeris mideclipse would take place on JD 2451870.04 =
November 21.54 UT.
Uncertainty is +/- 0.1 days, since our period of 45.150 days is accurate to
+/- 0.001 days.

This is a secondary eclipse and it lasts longer than the primary: 0.89 days,
so it will be visible from everywhere (I mean a "clear-sky everywhere"...)
although at different stages of the event.

I want to stress the point that this time THE LONGEST TIME COVERAGE BY EACH
OF THE  visual OBSERVERS will be needed  in order to correct for systematic
differences and be able to make a good determination of the time of minimum.
An isolate 2.1 estimate will be meaningless because that observer could be
estimating delta Velorum at maximum as always being 2.1...
So MAGNITUDES' ACCURACY is not very important for visual observations, but
consistency.
If some photometric observations can be performed, then that problem will be
solved and we'll have also a tool that will help us modelling the system
since we will know how deep the secondary eclipse is.

VISUAL OBSERVERS:
Don't let yourself be fooled by the ephemeris and WHAT IT IS SUPPOSED TO
HAPPEN...
Just trust your eyes and write down what you HAVE OBSERVED.

Comparison sequence:

Beta Carinae:   V= 1.67   B-V= 0.00
Gamma Velorum:  V= 1.70  B-V=  -0.25
Iota Carinae:    V= 2.24  B-V= 0.18
zeta Puppis:     V= 2.25  B-V= -0.27
kappa Velorum:   V= 2.49  B-V= -0.19

HD 76653    V= 5.705   B-V= 0.48 *
HD 76805    V= 4.685   B-V= -0.13 *

* Only for photometry.

Report your observations as soon as possible.
I hope we all have clear skies on monday and tuesday!!

Best wishes,
Sebastian Otero (LIADA),
Buenos Aires, Argentina.

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