Subject:
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Re: The "geography" of local space
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Newsgroups:
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lugnet.space
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Date:
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Sun, 7 Nov 1999 00:50:29 GMT
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Viewed:
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964 times
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John J. Ladasky Jr. wrote in message <3822B586.38355581@my-deja.com>...
>
> There is better data, and it was collected just two years ago. The • Hipparcos
> satellite, a project of the European Space Agency, took trigonometric
> measurements of stellar positions from space, above the atmosphere.
>
> http://astro.estec.esa.nl/Hipparcos/
>
> Hipparcos measured distances accurate to 10% at 100 parsecs. Distances to • 10
> parsecs are accurate to one percent! The only shortcoming of the data is • that
> the dimmest stars, below a visual magnitude of 12, were not observed. So • many
> of those nearby red dwarfs that I mentioned in my first post are not in the
> data set.
>
> ESA has placed the Hipparcos data on-line. However, the search program • that
> they have provided only allows you to look up stars by name or by position • on
> the sky -- not by distance. So it's no easy matter to make a 3D map of • local
> space.
What it does do, however, is give a link to the VizieR service that I found
a couple of years ago when I was investigating this very issue, creating an
accurate map of "our stellar neighbourhood".
The search page I used was:
http://vizier.u-strasbg.fr/cgi-bin/VizieR?-source=I/239/hip%5Fmain
Basically this allows you to query the Hipparcos database for all stars with
a measured parallax above a certain value (i.e. within a certain distance).
I suspect that you could even specify how large the error in measured
parallax should be, in your query. It's reasonably sophisticated.
However, I have done this already, and believe me, it's no easy task
downloading a "comprehensive" list of stars greater than 5 milliarcseconds
parallax ("comprehensive" meaning spectral type, apparent magnitude,
multiple system, and other info per star). The total list totalled more than
7 megabytes of plaintext and required about ten separate queries carefully
calculated so that the browser didn't chuck it on the size.....
I finally downloaded the list, though, and it's pretty much definitive. All
that is required is for somebody to write a program to read all entries in
from its text file and display the stars using 3-d coords based on RA,
declination and 206264.81/parallax, all of which is fairly straightforward
;-) This is what I myself planned to use the data for, but I lost interest
somewhat, and if any of you are more interested and have the requisite
programming ability then feel free to use this data yourself. A more
adventurous programmer could utilise the parallax error to draw a line for
each star showing how "inaccurate" its distance calculation is.
I've made a 1.8 meg PKZIPped file of this list called stardata.zip and put
it on my yahoo-geocities page (see below). See the line near the top called
"TECHNICAL INFORMATION". (PKZIP is a DOS program, I recall, but I think that
Winzip will read it).
Anyone let me know if they have any luck with this!
Paul
[My page: http://www.geocities.com/Area51/Shuttle/5168/ Update soon!]
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Message has 1 Reply:
 | | Re: The "geography" of local space
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| (...) I just had a look at this. Cool! This is the query engine that seemed so obvious to have, that I hoped would exist, but which was somehow missing from the main Hipparcos pages. I can see that the catalog contains some errors that have been (...) (25 years ago, 7-Nov-99, to lugnet.space)
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Message is in Reply To:
| | Re: The "geography" of local space
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| Hello again, I''m glad I generated some interest here! I hope, however, that we do not stray too far from discussing LEGO -- I have noticed complaints in at least one other LUGNET newsgroup. (...) Both quite rewarding, but difficult fields in which (...) (25 years ago, 5-Nov-99, to lugnet.space)
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