[vsnet-chat 1622] Re: [AAVSO-DIS] Re: FASTT-2 variables

[dhkaiser@sprynet.com (Dan)]

Brian, Brian, Brian.  I certainly did _NOT_ say "Hipparcos discovered all
the bright variables, and there's nothing left" or even words to that
effect!  I would be the last one on earth to say this!  I was told all the
bright variables had been discovered when I started my patrol 10 years ago.
My own experience proved otherwise and I will not now say that has changed!
I did say, or thought I did, that there are fewer to be found with
photographic patrols, so few that I felt it not worth the additional effort
required.  This pertains to PHOTOGRAPHIC patrols similar to mine.  That is
11th mag and brighter.  Of course CCD's will detect more new variables.  I
do not dispute this at all.  I'm sure it's true!  

I'm also pretty sure that the _majority_ of the CCD discoveries brighter
than 10th mag will have amplitudes less than 0.5 mag.  This makes visual
follow up observations difficult at best, not possible more likely.  It was
visual observations from the likes of Marv Baldwin and Tim Hager that
helped determine periods for many of my variables.  David Williams is
responsible for the majority being given official designations from his
investigations in the Harvard plate collection.   If it had been left up to
photometric observations to determine types and periods for these
discoveries, most would still qualify for the suspect variable catalog
only.  

If new discoveries are of small amplitude or fainter than say 12th
magnitude, it is probable that the majority will not be typed and have
periods determined.  I site Mike Collins' work in Great Britain.  He has
discovered well over a hundred new variable stars.   Most 11th mag or
fainter.  The last I saw few had been typed with periods.  Most  of his and
the FASTT variables will have to wait for the continuous all sky automated
CCD patrols to come on line before they will be properly studied.  This is
not going to happen next year.  Or even the one after that.

Yes there is a real allure to having made a true discovery.  However I have
gained much satisfaction from publishing a newly determined period.  Or
typing an suspected variable.  There is much work to be done.  So yes I
agree when you say  "A sharp telephoto and CCD is the way to go to clean up
the variable-star database."   Give me a  first grade 2k x 2k  super cooled
CCD with a top quality wide angle lens and I will be the first to get
started!  In the mean time there is much work the visual observers can and
will do.

Dan


On Sun, 7 Feb 1999 12:23:14 -0700, Brian wrote:

>     Dan Kaiser confirms the "received wisdom" that variables with
>amplitudes smaller than about half a magnitude are difficult to detect
>reliably using photography.  However, sky patrols using CCD + telephoto
>lenses clearly have an advantage, as has been recently shown by Pojmanski,
>in picking up variables with full amplitudes down to a few percent.
>I would counter Dan's claim that "Hipparcos discoverd all the bright
>variables, and there's nothing left", or words to that effect.  In brief,
>the more I use the Hipparcos database, the more I distrust it.  It did not
>find HD 23642, an Algol binary in the Pleiades, for instance, and resulted
>also in a lot of spurious variables, such as Altair and the fainter star
>star mentioned in recent 'vsnet' posts, which also probably spurious.
>Also, because of the way the stars were observed temporally, the observations
>were actually not very good for picking up variables nor sampling lightcurves.
>There's still plenty of work to do using the simplest of CCD set-ups (if
>that's not an oxymoron!).  As Arne Henden has mentioned, the several
>thousand FASTT variables have merely been detected, and few have anything
>like a reliable lightcurve or period-determination.  A sharp telephoto and
>CCD is the way to go to clean up the variable-star database.
>
>\Brian

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