<p>I'm using the Hipparcos catalogue in a software that I'm developing and I'm wondering if it is possible to know the RA and DEC of a star in the past or in the future. Maybe using the Parallax value.</p>
<p>Is that possible using this catalogue? Maybe, I need to use another one.</p>

CC BY-SA 4.0
2024-09-23T16:03:36.140Z
You would need the proper motion as well which wasn't very well measured for many stars by the Hipparcos satellite and mission due to the limitations at the time. You will have better success with the [Gaia DR3 catalogue](https://www.cosmos.esa.int/web/gaia/data-release-3) which was the successor to Hipparcos with orders of magnitude more stars and better precision.
astrosnapper
CC BY-SA 4.0
2024-09-24T01:33:31.947Z
When astrosnapper says "wasn't very well measured" he meant "way more precise than anyone not doing astrometry needs".  This is one of those "if you didn't already know about the GAIA catalog, you probably don't need it".  You should give it a look and see if it meets your needs better.  But the Hipparcos catalog is still more than enough for a lot of amateur applications.
Greg Miller
CC BY-SA 4.0
2024-09-24T10:14:18.060Z
@GregMiller Thanks for your comment. I know the CAIA catalog, and probably I will use it in the future. But, if I can use Hipparcos to calculate the RA and DEC of a stars many many years ago, I will use it. If not, I will use GAIA. Thanks a lot.
VansFannel
CC BY-SA 4.0
2024-09-24T16:57:10.700Z
It's really just a matter of applying the propper motion to get the new RA/Dec, you only need to use parallax if you want to account for the Earth's position relative to the solar system barycenter.  So it depends on what your needs are.  GAIA has 3d propper motion, where Hipparcos just has 2d.  So GAIA will be more accurate.
Greg Miller
<star><declination><right-ascension><spherical-astronomy><hipparcos>
Know the right ascension and declination of a star in the past using the Hipparcos catalogue
VansFannel
# Know the right ascension and declination of a star in the past using the Hipparcos catalogue

(Asked by: username_0 on 2024-09-23)

I'm using the Hipparcos catalogue in a software that I'm developing and I'm wondering if it is possible to know the RA and DEC of a star in the past or in the future. Maybe using the Parallax value.

Is that possible using this catalogue? Maybe, I need to use another one.

**Tags:** star, declination, right-ascension, spherical-astronomy, hipparcos

> **Comments:**
> **username_1**: You would need the proper motion as well which wasn't very well measured for many stars by the Hipparcos satellite and mission due to the limitations at the time. You will have better success with the [Gaia DR3 catalogue](https://www.cosmos.esa.int/web/gaia/data-release-3) which was the successor to Hipparcos with orders of magnitude more stars and better precision.  
> **username_2**: When username_1 says "wasn't very well measured" he meant "way more precise than anyone not doing astrometry needs".  This is one of those "if you didn't already know about the GAIA catalog, you probably don't need it".  You should give it a look and see if it meets your needs better.  But the Hipparcos catalog is still more than enough for a lot of amateur applications.  
> **username_0**: @username_2 Thanks for your comment. I know the CAIA catalog, and probably I will use it in the future. But, if I can use Hipparcos to calculate the RA and DEC of a stars many many years ago, I will use it. If not, I will use GAIA. Thanks a lot.  
> **username_2**: It's really just a matter of applying the propper motion to get the new RA/Dec, you only need to use parallax if you want to account for the Earth's position relative to the solar system barycenter.  So it depends on what your needs are.  GAIA has 3d propper motion, where Hipparcos just has 2d.  So GAIA will be more accurate.  

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