faint obsessions

[Fraser Farrell <fraser@trilobytes.com.au>]

Tom wrote:
>  If we don't go as deep as we can, then we run the risk of 
>  only measuring previously well studied objects.


A huge number of brighter and supposedly "well studied" stars have
only received serious scrutiny for a short time. Sometimes only on a
single night or two. Then the observing team's funding or telescope
time runs out, or they get told to Do Other Things by their masters.
Meanwhile, much of the infrequent or long-term behaviour of their
targets has been missed - simply because they weren't observed at the
"right time". This problem is well known to variable star observers.

There's also a tendency by many people to regard catalogues as written
in stone, so they are dismissive of follow-up observations of known
objects. The GCVS for example is neither complete nor definitive, even
for bright stars. Some examples from my half of the sky:


 - The recent recognition of Delta Vel as an eclipsing binary, using
only the astronomer's most ancient instrument. The lightcurve clearly
indicates an eccentric orbit, and there are known to be other
(spectroscopic) components. We would expect to see precessional
effects in this system.

 - The continuing mystery of BL Tel. Every 2.1 years it fades from mag
6.0 to about 9.4. These eclipses vary significantly in duration and
lightcurve. Why?

 - BR Cru, a mira-type variable which peaks at 7th magnitude, has
almost doubled its period since its discovery. Is there a rare helium
flash event in progress? Or are we seeing an equally rare switch from
double-mode to single-mode pulsation? There are thousands of mira
variables which have never been studied since their discovery. Which
was typically done with cameras that couldn't get past mag 13. Some of
these miras may be doing interesting things right now; and TASS could
see them doing it.

 - NSV 6708 has listed photographic magnitudes of:  9.7 (0.8). Sounds
boring doesn't it? It was not until the late 80's that this star was
identified as the third-brightest RCB variable in the sky (after R CrB
and RY Sgr) - with a true range of 7.1V to below 15 - and it's one of
the most active. There may be others like V854 Cen, waiting to be
found.

 - And on a personal note, I'm regularly observing some neglected
southern variables with binoculars. Some of them have already departed
significantly from their "well studied" characteristics. I'm also
following a few of the new Hipparcos variables with binoculars. AFAIK
I'm the only observer of some of these stars.


One of the strengths of TASS is its ability to do repeated and
internally consistent observations of stars over long periods of time.
Something that amateur astronomers can excel at, and what you need to
do to make these kinds of discoveries.

Don't get obsessed with trying to outdo the faint limit of LINEAR and
its ilk; there's no need. The Hipparcos satellite only went to
magnitude 12 and it found thousands of new variable stars. Many of
which are crying out for follow-up observations so that we can figure
out -what- they really are.

Even that notorious yardstick of professional success - the number of
citations in publications - could not ignore TASS. Who else is about
to survey the two million or so brightest stars, in multiple
passbands, virtually 24 hours a day for the next several years?

Our biggest challenge isn't going faint. Our biggest problem is doing
something useful with the 3 GB per TASS per night!



cheers,
Fraser Farrell