Hi all,
now that this great original site is back...
I would like to stimulate a discussion about possible strategies in
preparing stc files for binary star orbits in Celestia.
While Grant and I have exchanged plenty of emails about this
important issue during the last week or so, I would like to also find
out how people feel in the forum.
Let me set the stage:
Of course, it takes only a fraction of a second
to
randomly generate huge stc files with ficticious multiple star
orbits. Thus, for all people who are focussing their interest on
fictional systems, there is no problem whatsoever. Just switch to
another thread
.
But the situation changes drastically, as soon as we claim to model
large amounts of known multiple star sytems as
realistically as
possible in Celestia. Grant and I both adhere to the latter philosophy, but
our line of attack tends to be quite different.
Let me briefly explain (Grant will probably comment in his own way):
1) Grant has completed so far the 'nearstars.stc' file that includes
all prominent multiple star orbits out to some
maximum distance from our planet.
2) I have so far converted 2 published and much cited data sets for binary stars,
with close to 250 binary orbits in total:
a) S. Soederhjelm(1999)[visual] and
b) D. Pourbaix(2000) [spectroscopic].
(cf my post above this one!)
Many more are in the works...
Let me next describe
from my point of view the positive and
negative aspects of the methods we both have applied so far:
(1): Grant's approach of including /all/ multiples out to some maximal
distance is very sound as a strategy. I really like it! However, to
achieve his aim of
completeness, he has to
combine information from
various sources and 'hand-edit' many individual stars in his list
using numerous little pieces of data. The result implies a total loss of
transparency of analysis. The origin of his data can hardly be
traced anymore and inherent uncertainties are hard to
characterize/localize. On the other hand, the more Celestia's fame will grow, the
more conscious we will have to be as to citing data sources...
In summary: From a purely scientific point of view there is a
high price to pay for realizing this beautiful and most sensible aim.
(2): My attitude, so far was rather to put ahead the idea of
"data
purity". In practice this means that I "mass-convert"
(well-known) complete scientific catalogues by means of PERL scripts to Celestia
without modifying anything compared to the originals.
But also here the price to pay is high!
a) these attempts represent a highly random selection of a real
minority of all multiple systems in the sky. This continues to
bother me! It is conceptionally an analoguous dilemma as in case of
galaxies and nebulae.
In XEphem we had instead incorporated the entire WDS catalogue,
hence practically /all/ known multiple systems were identified as
such in our 2d(!) charts. The WDS catalogue, however, contains by far
insufficient information for a 3d orbit reconstruction.
b) Clearly, with my "strict" approach there will be plenty of "empty
slots" in the resulting stc files, since most of the catalogs
either lack the m_B/m_A mass ratios, the spectral classes or the
visual magnitudes of the secondaries here and there . Of course,
there are still quite a few possible measures that would alleviate these
problems, but they would require quite a bit of respective coding
(by Chris typically
).
One can easily merge various entire catalogs together and logically
correlate their complementary contents via the ID's of the stars.
Such a procedure does indeed preserve scientific transparency,
since it is easy to globally state the applied procedure in one or
two sentences. What is a crucial requirement for data purity,
however, is that none of those /input/ catalogues would be modified
in any way relative to their published contents. Hence the
"patching" has to be done either through intermediate file
generation or internally. And that's where Chris has to come in...
So let us know what you think. But I emphasize again: this whole
discussion is based on the presumption to try and do a job as close as
possible to reality...
Oh yes: what I hope for is not a "judgement" of what
method you like better. Rather I would very much
welcome any suggestions of how you think the described
problems of either method could somehow be cleverly
circumvented!
Bye Fridger