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Tales of Cataloguing XIV -- the 0th finding chart



 
 
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Old January 10th 19, 06:56 AM posted to sci.astro.research
Eric Flesch
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Default Tales of Cataloguing XIV -- the 0th finding chart

(This and the previous posting are because I've recently found & fixed
a few more mis-positioned legacy objects -- there's always more if you
look hard enough, it seems. I give the more interesting ones here,
for the record.)

20th century quasar discovery papers made liberal use of finding
charts to display the precise location of new quasars, lest the listed
co-ordinates weren't accurate enough. Astrometry had much improved by
the 1990s but finding charts were still usually included, more as a
tradition than a necessity. That was all fine so long as the listed
astrometry and finding chart agreed. But sometimes they didn't.
Sometimes they pointed to different objects.

I've given examples of this in earlier postings in this series,
notably #VIII "the log of jumping up & down" which is what you do
when bad finding charts drive you crazy. But other times it is good
finding charts which save the day when the listed co-ordinates are
false, e.g., the quasar "TOL 1038.2-27.1" from Bohuski & Weedman
1979,ApJ 231,653, object #23 (last one in the list), 41 arcsec offset
from the false listed co-ordinates (unsuitable photometry r=18.0
b=20.1) to the true finding chart object (r=19.2 b=19.5). Another
example is the quasar "Q 0111-328" from Savage et al. 1984,MNRAS
207,393, which gave finding charts onto the original prism (grism)
plates which are infallibly correct because the actual discovery
spectrum is pointed at; the B1950 co-ordinates given in the
microfiche were of a nearby object offset by 76 arcsec. Even big
names like Schneider/Schmidt/Gunn did this for one object, "PC
0027+0515" in 1999, AJ 117,40, the Table 5 co-ordinates of which
pointed near random objects whilst the true object was revealed on the
finding chart at an offset of 17 arcsec.

So there were bad finding charts and good finding charts. But then
there's this, from Borra et al. 1996, AJ 111,1456, the quasar "Q
13034+2942" (called "130324+294245" in the paper) is the very first
one on their list, and their first finding chart. They would make no
error on the very first object, right? Of course not. Furthermore,
on their Table 4a they lead right off with it as positioned at B1950
130324.21+294245.8, lest there be any mistake. That translates to
J2000 130547.40+292643.0 which shows up on the SDSS finding chart as a
flattish-spectrum 21-mag stellar-psf which my own data reports as a
variable object which was 19th magnitude in the 1960's -- so very
quasar-like and all good. So why did I previously have it catalogued
as a reddish v=22 object 17 arcsec to the South-West? Let's have
another look at that finding chart, the first finding chart of the
paper.

There it is, but wait, they are pointing to the reddish object (which
is probably a red dwarf star). This is one of those finding charts
where they don't use a photo, instead they re-create it with ink on
paper. Looks like they used a plotter (remember those?) and optical
data. Um, guys, your optical data did not include the true object.
It's not there at all. They're pointing to the red dwarf because the
quasar isn't on the chart. Their very first finding chart for quasar
discoveries points to a red dwarf star. Looking at my archived
catalogue versions, I originally had the right identification
(inherited from VCV) but switched it to the red dwarf just before the
publication of my Half-Million Quasars catalogue. Guess I'd looked at
one finding chart too many.

Well, that's no kind of first finding chart to have, is it? Maybe if
the authors can "promote" it to the zero-eth finding chart, it will go
away. And these are the kinds of Finding Chart Follies that I've
encountered through the years.
-------

On a separate note, the Soviet quasar "Q 0752+617" from
Afanasiev/Lorenz/Nazarov 1989, SvAL 15,83 does not exist. I've looked
for it for years. I've communicated with the lead author and he
doesn't know where it is -- he knows only the old VCV location which
is just the B1950 sky rectangle denoted by "0752+617". There is no
radio, no X-ray, no WISE candidate, no suitable bluish optical. The
paper stated narrow emission lines -- perhaps they measured a galaxy.
I give up, it is removed from the Milliquas catalogue as of the next
edition. I will gladly restore it if the authors provide its
location.

Eric Flesch
10-Jan-2019


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