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(IAAC) Open Cluster catalogs and xrefs



Hi Lew and everyone,

I now have 'version 1.0' of a list of 1240 open clusters with perhaps 1000
cross-references to catalogs other than their 'primary' designations. I
created this list by doing something along the lines of:

1) Putting the Lynga catalog in a table;

2) Adding the Alter and Ruprecht catalogs and aligning them across records
but putting them into discreet fields, and doing the same for OC's from NGC
2000,

3) Tossing in all the OC's from the Saguaro Astronomy Club database just
for good measure (the SAC database provides some xrefs to the Herschel
lists, which might be useful).

Not mentioned in detail is a lot of evaluation I did of various other
catalogs that I considered adding to this project. All were rejected since
they were shown to be entirely redundant. At this point I did some error
checking, with the help of the listmembers here, and did some spot-checking
to see if any of my fields wandered into the wrong records - all looked
well. After taking a short break for some minor surgery, I resumed and:

4) wrote (and rewrote several times - what can I say, I am no programmer)
and ran a program that checked all the xref fields for duplicates in the
key fields,

5) chose which duplicate to keep based on the following rules: NGC-IC was
always kept as the key when one of the xrefs was in these catalogs; when
all three of the source catalogs agreed on a name for the cluster I kept
that one; otherwise I went to a journal searching site and checked to see
what designation was most popular in the literature of the last ten years,
and kept that. Belatedly, I realized that Messier numbers end up as xrefs
only, and not keys, but there aren't too many and I think I can manually
work around that if keys on Messier number are desired. Then I

6) removed the discarded duplicate record and all its fields to another table.

Now what I have is a table with some pretty good keys, and xrefs that allow
one to reconstruct practically every old catalog in full from the secondary
sources if one so desires. The formatting leaves a little to be desired at
this point, as not all the xrefs are aligned to the lowest possible field,
but I can clean that up pretty easily.

If all you want is the list of xrefs, Lew, I can send it now. What format
would you like? Is comma-delimited OK?

A couple surprises came up in the process of putting this together. The
main surprise was that there are a couple of clusters that are commonly
referred to in the amateur literature by a Collinder or Tombaugh name that
bear NGC or IC numbers. I have set these cases aside to investigate more
closely; there is no particular reason that the cross referencing sources I
used are infallible, and these cases are particularly well suited to
checking up on. Next trip to Tucson....

Future plans (when there is time) are to expand this to include all the
data normally useful to an amateur observer for each cluster. This will be
a little more difficult, since positions/magnitudes/sizes in various
catalogs vary somewhat, and combining data from four or more sources
necessitates making a lot of 'manual' choices if it is to be done
intelligently. If anyone has any ideas or advice for that part of the
process, I am all ears.



--
Jeff Medkeff          | Acting Assistant Coordinator
Rockland Observatory  | Association of Lunar and Planetary
Sierra Vista, Arizona | Observers, Solar Section

On the web at http://shutter.vet.ohio-state.edu/
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