[vsnet-chat 3898] re Re id. of LMC star HDE 269927

[crawl@zoom.co.uk]

The best bet for such things nowadays is to use Vizier, the DCMC for the
LMC, and then Aladin.

Or, to be less cryptic, go to the CDS at Starsbourg's website
[http://cdsweb.u-strasbg.fr], select the Vizier link, from the top dialogue
search for DCMC, from the few options choose the LMC mentioning catalogue,
put the co-ordinates in for the object as best known, and try a one arc
minute radius.

You get about a dozen and a half candidates.  When you've got them, select
the Aladin option at bottom to plot the DCMC objects.  When that has
loaded, select the load button from the Java applet, submit and select the
MAMA/CAI R high resolution plate, which will then load as overlain by the
DCMC objects.

Of course, in this instance, and out of perversity, no exact fit works for
the co-ords Matti gave.  Also, the best magnitude you're going to get from
the DCMC is gunn I, but if you've got enough information about your star,
you can get a good idea what is what.  It just takes a bit of work.

The Vizier data can be leached out and plotted up in Guide 7 a doddle via
TDFs.  I've done it in the past.  The DCMC stuff is good to about an arcsec
or two.  There's often 2MASS positions for LMC and SMC stuff too, which can
also be plotted up in Guide or similar.  Astrometry here is also good to
about 1 arcsec.  I've plotted up 2MASS objects and real sky images in Guide
for the LMC before, whilst idly checking ASAS variables against GCVS vol V
variables [as ASAS didn't appreciate that a lot of their new LMC variables
were already known].  Again, 2MASS photometry is near-infrared, so you've
to be careful how you compare these to visual magnitudes, if at possible at
all, but suddenly when you start getting good enough plate images and also
_lots_ of astrometric positions, which both DENIS and 2MASS ooze with, then
matching objects up is just the old fashioned eye-brain patter fitting
whilst looking at an extended area.

Anyway, it works, and it's online, so it's available even if you haven't
got CDs or books or plate archives to hand [having Guide 7 helps, but you
don't need that either].

John

JG, UK

PS

And I didn't even bother getting UCAC1 out... ...but that's not available
online.

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