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PostPosted: Sat Feb 04, 2012 5:58 am 
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EDG wrote:
Or you could just use the data I've already processed here as it is, and not have to do any calcuations at all.

True, but equally I could use the data that I've already processed, added metallicity and age data to, added component and orbital data to from the Internet Stellar Database, correlated with different sets of proper names and durchmusterung identifiers, etc., filtered to remove stars that are not plausible primaries for habitable worlds from, etc.

I gathered from your page that your lists only have a single entry for each multiple star system. Is that right?

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PostPosted: Sat Feb 04, 2012 6:37 am 
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Yep. This is largely a positional database (the RECONS stuff has more physical data though). The stars aren't even the correct type in the Hipparcos datasets (because the spectral type isn't provided), though they do have the correct Bayer names if they exist for that HIP number.

Well, if you've got all that already then I'm not sure why you even need to be looking at my mapping page - though I'm not sure how accurate the data on the Internet Stellar Database is (does it use the new reduction of Hipparcos?)

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PostPosted: Sat Feb 04, 2012 7:02 am 
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EDG wrote:
Well, if you've got all that already then I'm not sure why you even need to be looking at my mapping page


Until I looked at it I didn't know that know that I didn't need to look at it. I had hoped that you might have got onto a more recent and complete data source than I have.

Quote:
- though I'm not sure how accurate the data on the Internet Stellar Database is (does it use the new reduction of Hipparcos?)


ISDB is a collation of data from different sources, with the source separately noted for each datum. For example, the source for the parallax for Sirius (first thing I thought to check) is noted as "Hipparcos". For what it's worth it lists the position of each star three times: once as right ascension, declination, and distance, once in "celestial" (i.e. equatorial) X, Y, and Z, and once in "galactic" X, Y, and Z. But these aren't stored separately in the database, the conversions are done on the fly by the query script. (I note that it has defined galactic co-ordinates slightly differently from you.)


For anybody who might be interested, here is a picture showing the Galaxy projected onto the base plane of the "galactic" co-ordinate system. For what it is worth, my entire setting is mostly confined to the little white circle labelled "Sun".

Image

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Last edited by Agemegos on Sat Feb 04, 2012 11:13 am, edited 4 times in total.

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PostPosted: Sat Feb 04, 2012 7:39 am 
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I don't think the ISDB is using the updated New Reduction of Hipparcos that I'm using. From what I gather the New Reduction is a refined version of the original catalogue, and was released in 2007. Some of the stellar data has been altered in the New Reduction, but I don't know which stars were changed.

e.g. Sirius was last updated in ISDB in 2001, but its data appears to be similar to what it was then. However, more accurate data for Sirius can be found in the RECONS data along with all the other stars within 22ly of Sol (RECONS was updated in Jan 2012), which is also on my mapping page.

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PostPosted: Sat Feb 04, 2012 9:17 am 
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By the way, I did not follow the latest developments, do we
now have accepted distance data for the Pleiades ?


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PostPosted: Sat Feb 04, 2012 10:08 am 
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We have more accurate data, they seem to be at aroun 400ly according to the New Reduction of Hipparcos.

Incidentally, my next blog update (hopefully this weekend) will tell you how to make a corridor from Sol to the Pleiades!

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PostPosted: Sat Feb 04, 2012 9:52 pm 
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Cool, look forward to whatever data you chose to share out. I'll have to look at grabbing your data to replace the data that I've used for the stars that are in both our data. In doing so, certainly one advantage to using GCS is that I can just replace my XYZ for a star with yours, no calculations necessary. Unfortunately, your data is too different from my data for my duplication algorithm to merge our data sets automatically. It determines duplicate if within .1 pc, which perhaps actually should be some percentage of the distance from Sol.

My data probably is a bit of a bastard having grabbed data from different catalogs. Obviously that isn't good from a purist standpoint, but perfectly ok for setting up a game universe, especially considering that really, beyond the nearby Sol area, 95% or more of the stars that will actually be used in the campaign are made up stars, using the real stars just as convenient labels for areas of space (though maybe I'll set up some kind of system where it is possible to make really long jumps if your target is a very large star).

Frank


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PostPosted: Sat Feb 04, 2012 10:09 pm 
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Yeah, merging catalogues is a bitch... I made no attempt to do that here - it was fiddly enough to replace the HIP numbers with the Bayer/Flamsteed star names where I could do that! Also, it's not advisable to mix them because the parallax measurements have different levels of accuracy between catalogues.

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PostPosted: Sat Feb 04, 2012 11:56 pm 
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New article!

http://evildrganymede.net/2012/02/04/ma ... -database/

In which I describe how to use the VizieR database to make your own stellar database with Galactic XYZ co-ordinates (and how to import it into Astrosynthesis too)! The example provided is a corridor between Sol and the Pleiades (2300AD fans will recognise this as the Bayern corridor!) - I've also added this dataset to the Stellar Mapping page so you can download it from there!

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PostPosted: Sun Feb 05, 2012 10:15 am 
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If you've downloaded the RECONS dataset from the Stellar Mapping page, please download it again! A missing star system (Gliese 667) has been added!
(gory details can be found at: http://evildrganymede.net/2012/02/05/st ... t-updated/ )

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