Where can I download the locations and magnitudes of the thousand or
so brightest stars/galaxies?  I would like a file with the celestial
lat/lon of each star, and its brightness.

Distances to the Sun and Stars
http://www.uwgb.edu/dutchs/CosmosNotes/distance.htm

"the *Hi*gh *P*recision *Par*allax *Co*llecting *S*atellite
[HIPPARCOS], was launched by the European Space Agency [ESA]. Despite
an engine malfunction that left the satellite in a less desirable
orbit than planned, the spacecraft gathered data on stellar positions
and magnitudes until March 1993. The data were processed and finally
released in catalog form in the summer of 1997. The data are of
unprecedented accuracy and have completely revolutionized the
determination of stellar distances.

Hipparcos worked by observing stars through two telescopes aimed 58
degrees apart. The light from the two telescopes was merged into a
detector with a fine grid of wires. As the satellite rotated,
different stars passed through the field of view of each telescope and
blinked on and off as the stars passed across the grid of wires. These
observations allowed extremely accurate relative positions of the
stars to be determined. The relative positions of all the stars could
then be combined into an extremely accurate catalog of star positions
across the entire sky.

For 118,000 selected stars, Hipparcos measured their parallax accurate
to .001 second of arc. That's the apparent diameter of a quarter at a
distance of 5000 kilometers, or putting a quarter in New York and
viewing it from San Francisco. It's also the amount the hair on a
person a meter away appears to grow in one second. A secondary mission
named Tycho measured another million stars to an accuracy of "only"
0.01 second."


The Hipparcos Space Astrometry Mission
http://astro.estec.esa.nl/Hipparcos/

The Hipparcos and Tycho Catalogues Tools for interrogating the Catalogues
http://astro.estec.esa.nl/Hipparcos/research.html

Multiple tools to extract data from the catalogues.


The Hipparcos and Tycho Catalogues Multiparameter Search Tool
http://astro.estec.esa.nl/hipparcos_scripts/hipMultiSearch.pl

Allows searches of the HIPPARCOS, Tycho, and Tycho-2 catalogues.


ReadMe
This is the README file for the Hipparcos and Tycho Multiparameter Search Tool
http://astro.estec.esa.nl/Hipparcos/pstex/ReadMe.hsearch


The Hipparcos and Tycho-1 Databases
ftp://cdsarc.u-strasbg.fr/pub/cats/I/239/

Download the databases.


The Tycho-2 Database
http://www.astro.ku.dk/~erik/Tycho-2/


SEARCH TERMS

://www.google.com/search?q=high+precision+parallax+collecting+satellite&btnG=Google+Search&hl=en&lr=&ie=UTF-8&oe=utf-8&safe=off


hlabadie-ga

---

Request for Answer Clarification by racecar-ga on 03 Dec 2003 14:27 PST

I tried to search for all the stars in a given magnitude range using the tool at

http://astro.estec.esa.nl/hipparcos_scripts/hipMultiSearch.pl

but it just keeps giving me "segmentation fault".

---

Clarification of Answer by hlabadie-ga on 03 Dec 2003 15:05 PST

I just searched for all objects between magnitude 2 and 5, and got
this (the formatting will be off):

Fields and parameter search limits:
B-V: Min 2.0 Max 5.0

333 entries satisfied your request.
0|H1          |2|H3         |H4         |H5   |6|7|H8          |H9    
     |0|H11    |H12     |H13     |H14   |H15   |H16   |H17   |H18  
|H19  |H20  |H21  |H22  |H23  |H24  |H25  |H26  |H27  |H28  |H29|H30 
|H31   |H32   |H33  |H34   |H35  |6|H37   |H38  |9|H40 |H41 |2|3|H44  
 |H45   |H46  |H47|8|H49  |H50  |H51    |2|3|4|H55      
|6|57|58|9|0|1|62|H63|H64    |H65  |H66  |H67 |8|9|0|H71   |H72      
|H73       |H74       |H75 |H76         |7
H|          99| |00 01 15.84|+60 21 19.1|
7.04|2|H|000.31601620|+60.35529798| |   1.27|    9.57|   -6.49|  0.47|
 0.51|  0.70|  0.55|  0.57|-0.10| 0.06| 0.15| 0.13| 0.01|-0.03| 0.03|
0.03| 0.26|-0.10|  0| 0.52|    99|11.006|0.055| 7.383|0.006| |
2.835|0.040|T|2.91|0.04|L| | 6.9749|0.0143|0.157|153| | 6.77| 7.21|   
   |U|2|B|00013+6021|I| 1| 1| | |S|  |   |       |     |     |    | |
| |224855|B+59 2810 |          |          |2.85|C5p         |G
H|         363| |00 04 36.41|+43 33 04.7|
8.12|2|H|001.15170942|+43.55131855| |   2.15|   -4.57|   -2.54|  0.70|
 0.58|  1.05|  0.82|  0.58|-0.10| 0.04| 0.31| 0.24|-0.13|-0.12|-0.08|
0.35| 0.11|-0.24|  0| 0.70|   363|11.636|0.094| 8.430|0.011| |
2.530|0.069|T|2.59|0.07|L| | 8.1265|0.0116|0.102|126| | 8.01| 8.26|   
   |U|2|C|          | |  | 1| | |S|  |   |       |     |     |    | |
| |225217|B+42 4827 |          |          |2.51|C5II        |G
H|        1652| |00 20 43.56|+61 52 46.5|
6.80|2|H|005.18151870|+61.87959637| |   0.49|   -2.92|   -0.43|  0.51|
 0.53|  0.71|  0.67|  0.64|-0.07| 0.07| 0.16| 0.35|-0.02| 0.00|-0.01|
0.23| 0.08|-0.01|  0|-1.45|  1652| 9.367|0.017| 7.059|0.006| |
2.020|0.015|G|2.28|0.03|C| | 6.8537|0.0032|0.031|126| | 6.81| 6.91|   
   |U|2|C|          | |  | 1| | |S|  |   |       |     |     |    |S|
|P|  1613|B+61   43 |          |          |2.28|M2II:       |X
H|        1901| |00 24 01.96|+38 34
37.6|10.71|3|H|006.00816265|+38.57712054|*|  -0.06|  -16.33|  -35.00| 
3.72|  2.60|  6.49|  4.88|  2.47|-0.31|-0.02| 0.66|-0.21| 0.65| 0.85|
0.12| 0.54| 0.66| 0.48|  0|-0.22|  1901|      |     |      |     | |
2.080|0.510|G|2.63|0.57|K| |10.7054|0.0114|1.284| 82| | 8.04|11.01|
409.20|P|1|B|00241+3834|I| 1| 1|V| | |  |   |       |     |     |    |
|D|P|  1967|B+37   58 |          |          |2.63|S6,6ev      |G

[...]
(You get the idea.)


Try clicking on the box that precedes the magnitude entry boxes (a
check mark should appear), then enter values for the magnitudes and
click Search. If there are too many objects, you might get an error.
So try searching on a smaller set of the values you are seeking.

hlabadie-ga

---

Clarification of Answer by hlabadie-ga on 21 Jan 2004 14:45 PST

Some recent developments call the Hipparcos data into question,
illustrating the problems that affect the accuracy of estimates of
interstellar distances:

Caltech Astronomers Find Satellite Errors
http://apnews1.iwon.com/article/20040121/D807F6880.html

"The Hipparcos satellite, named after the ancient Greek credited with
inventing astronomy, was launched by the European Space Agency in 1989
and collected data for four years before it was shut down in 1993.
[...]
"In a study published Thursday in the journal Nature, Caltech
astronomers Xiaopei Pan, Michael Shao and Shri Kulkarni present
evidence that appears to confirm Hipparcos missed the mark by a
significant amount.

"Hipparcos is, in fact, systematically off from other estimates we
have," said William Van Altena of Yale University."

hlabadie-ga

Thanks

There are at least two star databases online. Here is the description of one:

"The catalogue contains high-quality positions and proper motions for
nearly one million stars. The median accuracy of the TRC position
component is 40 mas at J1991.25. The median accuracy of the proper
motion is about 2.5 mas/yr. The systematic errors are less than about
1.0 mas(/yr"

Would that work?

hlabadie-ga

hi hlabladie,

I'm not sure.  I want to write a simple program that will show what
the stars will like like if you look in a given direction from a given
location at a given time.  I don't want to have to look up the
location of each star individually, so I need a file I can download,
with data in a form that I can extract (like ASCII).  I also need
information on brightness.  This doesn't have to be at all precise,
but just some way to divide the stars into a handfull of categories
from brightest to dimmest.

Thanks.

Here is a quotation from the Readme documentation provided for the
databases. As you can see, it is possible to download 1000 entries at
a time, using a number of parameters, including magnitude.


"The user can request all entries from any of these catalogues which
satisfy a range of criteria. (A maximum of 1000 entries per search can
be retrieved at one time.) Below we list the parameters which can be
selected (for the users convenience we note also the range of values
which the parameters span; the search tool will only accept values
within these ranges):
From the Hipparcos and Tycho Catalogues: 
Right ascension (epoch J1991.25, ICRS): Field H8/T8 from the Hipparcos
and Tycho Catalogues, range [0,360];
Declination (epoch J1991.25, ICRS): Field H9/T9 from the Hipparcos and
Tycho Catalogues, range [-90,90];
Trigonometric parallax (in milliarcseconds): Field H11/T11 from the
Hipparcos and Tycho Catalogues, Hipparcos range [-55, 772.33], Tycho
range [-919, 701.5];
V magnitude (in the Johnson UBV photometric system): Field H5/T5 from
the Hipparcos and Tycho Catalogues, Hipparcos range [-1.44, 14.08],
Tycho range [-1.44, 15.2];
B-V (colour index): Field H37/T37 from the Hipparcos and Tycho
Catalogues, Hipparcos range [-0.4, 5.46], Tycho range [-1.037, 4.353];
From the Tycho-2 Catalogue:
Mean right ascension (epoch J2000, ICRS): bytes 16-28 from the Tycho-2
Catalogue, range [0, 360];
Mean declination (epoch J2000, ICRS): bytes 29-41 from the Tycho-2
Catalogue, range [-90, 90];
Tycho-2 V_T magnitude: bytes 124-130 from the Tycho-2 Catalogue, range
[1.905, 15.193]"

hlabadie-ga

Sounds promising.  Go ahead and post your answer.

Not sure why I was getting an error before, but it works now...

I'm glad that it worked out for you. Thanks for the rating.

hlabadie-ga