BRJ variable star observa



A > Subject: BRJ variable star observations
A > From: allisonki@xxxxxxxxxxx
A > Date: 8 Sep 2005 17:50:49 -0700

A > >Quite a number of contributors monitor these stars
A > >nightly, even though ones like XX Cam haven't shown any >brightness variation
A > in decades! Such over-observation simply
A > >serves to clutter the lightcurve and
A > >hide any true changes.
A >
A > But looking at the AAVSO "quick look" file, I see the following recent
A > observations for R CRB:
A >
A > R CRB SEP 08.0000 2453621.5 6.1 BRJ
A > R CRB SEP 07.0000 2453620.5 6.1 BRJ
A > R CRB SEP 06.0000 2453619.5 6.1 BRJ
A > R CRB SEP 05.0000 2453618.5 6.1 BRJ
A > R CRB SEP 04.0000 2453617.5 6.1 BRJ
A > R CRB SEP 03.0000 2453616.5 6.1 BRJ
A > R CRB SEP 02.0000 2453615.5 6.1 BRJ
A >
A > And these for XX CAM:
A >
A > XX CAM SEP 08.1000 2453621.6 7.3 BRJ
A > XX CAM SEP 07.1000 2453620.6 7.3 BRJ
A > XX CAM SEP 06.0000 2453619.5 7.4 BRJ
A > XX CAM SEP 05.1000 2453618.6 7.3 BRJ
A > XX CAM SEP 04.1000 2453617.6 7.3 BRJ
A >
A > Since R CrB has been at maximum for about three years now, and XX Cam
A > has shown no further activity (at least that I am aware of), I am
A > wondering, John, if you have re-considered your earlier advice
A > regarding observing frequency for such stars? Should I be observing R
A > CRB and symbiotic-type variables nightly?
A >
A > Thanks very much, since this is a matter I worry about a lot - whether
A > I am observing a particular star too often (or not often enough).

What Bortle, and others, mean is that a single particular observer
need inspect R CrB only once in five days. It does not imply that the
star is observed globally with that frequency. Given that there are
scores or hundreds of observers with R CrB in their program, the star
will get dialy monitoring. It's just that you, as a specific person,
had take a break for several days between inspections.
The phaenomenon of a projected '6.1' assessment for R CrB when the
star in fact startd its decline is one of the notorious features of
the observing record. Part of the cause is thhat an observer missed
this star for some reason (fatigue, clouds) and ASSUMED that the star
was still at normal brightness! When they get word that R CrB is on
the plunge, they go out and get actual assessments and the spurious
ones stop.
By spacing out your observations of a particular star you avoid
the 'rut' effect and partially 'erase' your recollection of the star's
brightness from the previous view. It is a MUST that you look at a
variable star with no prejudice from prior observations!
I'm sure this topic will come up at the obsrvation workshop at
AAVSO in Ovctober.
R CrB does not stay stable at normal light, as pointed out here
already. I does waver a couple tenths magnitude almost under the
detection limit of most obs ervers. It pays to examine the star and
the comparison stars carefully. SInce you record your assessment to
the full tenth magnitude, your own records in isolation may show
little variations. It's the cumulative reports from many observers
that builds up the true behavior of this star.

---
þ RoseReader 2.52á P005004


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