[vsnet-chat 3634] Re: Overobserving

["Ondrej Pejcha" <opejcha@volny.cz>]

Dear all,

>                   About the recent discussion on
overobservations for mira
> stars, I agree with the notion of not making estimates
every night.
> It's no use because of the long periods= the star is not
going to vary in
> just one day. The star is going to stay the same and maybe
observational
> error on our part will ruin a pretty nice lightcurve
filling it with noise
> that could have been avoided if we were patient enough to
wait for the star
> to actually vary.

I'm of an just opposite opininon. Lets assume model Mira
variable with period 300 days and amplitude 6 mag - star
will change with rate 0.04 mag/day (assuming sinusoidal
variation - lightcurve of Miras is similar), which can
single observer catch (of cource, only if magnitudes are not
rounded on tenths). And sometimes, the star varies quicker:
in August I caught ascending branch of R UMi. This
semiregular variable changed about 1 mag in eleven days!
Rate 0.1 mag per day can be easily observed with eyes.
Concerning the noise in lightcurve I have another example:
during August the semiregular variable AY Dra has faded by
1,5 mag. I covered this variation with 17 estimates: 3
estimates deviates from mean lightcurve by 0,3 mag. What
should I think if I instead of 17 estimates made only 6 (one
est. in 5 days) and 3 of them were wrong? Thus, I think that
large number of points in lightcurve can do very good job in
filtering deviating estimates. And if lightcurve has stabile
noise, some averaging might help.

Best regards,
Ondrej Pejcha

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