<p>Yes, in a way.</p>
<p>If you are looking (up) at the celestial North Pole, and could see the meridians, you would note that the angle of right ascension increases clockwise.</p>
<p><a href="https://i.sstatic.net/p1xgm.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/p1xgm.png" alt="enter image description here" /></a></p>
<p>On the other hand, if you were in space looking (down) at the North pole, you'd note that the lines of longitude increase anticlockwise.</p>
<p><a href="https://i.sstatic.net/dI9QS.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/dI9QS.png" alt="enter image description here" /></a></p>
<p>This is a result of &quot;looking up&quot; or &quot;looking down&quot;.</p>
<p>You could, I suppose, create a map of the Earth with the &quot;sub-stellar point&quot; (the point on Earth that is directly &quot;below&quot; the star&quot;) of each star (at a particular time/date) shown on the map.  If you did this, the constellations would appear mirrored from how we are used to see them.</p>

CC BY-SA 4.0
2022-05-15T16:12:57.427Z
Thank you for this informative and clear answer. Are you aware of any lists of sub-stellar points for stars? I imagine these move and so might be based on J2000 or something if there are lists. If that's not an option, do you think another appropriate answer to getting a view from "Outside" could be to change any longitude from east to west and vice versa? That should create a mirrored arrangement that is otherwise identical I think?
Harzard
CC BY-SA 4.0
2022-05-15T16:17:11.803Z
They move very fast!  They go all around the Earth every day. (because the Earth rotates)
James K
CC BY-SA 4.0
2022-05-15T16:42:46.753Z
By construction, on the spring equinox (21st March) the stars with a right ascension of 0h will be above the Prime Meridian at 00:00 UTC.  As one hour is 1/24 of a circle or 15 degrees, stars with a right ascension of 1h will be above the 15 degree meridan and so on. The declension of the stars corresponds directly to latitude, a star with a zero declension will be above the equator etc. So simply reversing longitude may get the effect you want
James K
CC BY-SA 4.0
2022-05-15T16:56:33.310Z
That helps a lot, think I'm getting there now! Just a quick further question if you have a moment. The Wikipedia star entries come with maps that apear to be from an "Outside" perspective, based on your explanation above, am I reading it right? https://en.wikipedia.org/wiki/Delta_Crucis the map goes counter-clockwise in terms of RA.
Harzard
CC BY-SA 4.0
2022-05-15T17:00:06.060Z
Ah,  but that is looking towards the southern pole, and around the south pole RA goes counter clockwise, and longitude goes clockwise.  So that view of the southern cross is also "looking up"
James K
CC BY-SA 4.0
2022-05-15T17:02:14.810Z
Take a look at https://starinastar.com/earth-map-in-the-sky/  It shows the Earth map projected onto the sky, and as expected, it is mirrored.
James K
CC BY-SA 4.0
2022-05-15T18:40:58.250Z
Thanks, having given that a read I'm not sure I followed all of it, but looking on google earth if I go to the poles I can see that longitude goes from clockwise to anti etc. I'm unsure about what I've created on google earth when I've added star coordinate waypoints to it. On my map if I look at the constellation Crux (useful for having four points in different directions), my Beta Crucis is on the right hand side when looking down at my google earth, but in the map on wikipedia it is on the left of the constellation. Does this mean I've already created the mirror image we are discussing?
Harzard
CC BY-SA 4.0
2022-05-15T19:56:46.350Z
"Does this mean I've already created the mirror image we are discussing"  Yes
James K
CC BY-SA 4.0
2022-05-15T15:28:11.450Z
2022-05-15T15:28:11.450Z
James K
<p>When reading up on celestial globes it talks about handedness and that many celestial globes are reversed so that the constellations appear as they do from earth.</p>
<p>I'm trying to arrange some bright stars on an overlay of the earth, using Right Ascension and Declination as Long/Lat. Am I right in saying that RA and Dec are essentially viewing the stars from &quot;within&quot; an imaginary map, and if so would an overlay be more accurate if you mirrored the image, so that the overlaid map is effectively being viewed from &quot;outside&quot; of the mapped system?</p>

<star-maps>
Are Right Ascension and Declination from an "inside" perspective?
Harzard
# Are Right Ascension and Declination from an "inside" perspective?

(Asked by: username_0 on 2022-05-15)

When reading up on celestial globes it talks about handedness and that many celestial globes are reversed so that the constellations appear as they do from earth.

I'm trying to arrange some bright stars on an overlay of the earth, using Right Ascension and Declination as Long/Lat. Am I right in saying that RA and Dec are essentially viewing the stars from "within" an imaginary map, and if so would an overlay be more accurate if you mirrored the image, so that the overlaid map is effectively being viewed from "outside" of the mapped system?

**Tags:** star-maps


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## 1 answers

### Answer by username_1 on 2022-05-15. Score: 1 | Accepted answer

Yes, in a way.

If you are looking (up) at the celestial North Pole, and could see the meridians, you would note that the angle of right ascension increases clockwise.

[![enter image description here](https://i.sstatic.net/p1xgm.png)](https://i.sstatic.net/p1xgm.png)

On the other hand, if you were in space looking (down) at the North pole, you'd note that the lines of longitude increase anticlockwise.

[![enter image description here](https://i.sstatic.net/dI9QS.png)](https://i.sstatic.net/dI9QS.png)

This is a result of "looking up" or "looking down".

You could, I suppose, create a map of the Earth with the "sub-stellar point" (the point on Earth that is directly "below" the star") of each star (at a particular time/date) shown on the map. If you did this, the constellations would appear mirrored from how we are used to see them.

> **Comments:**
> **username_0**: Thank you for this informative and clear answer. Are you aware of any lists of sub-stellar points for stars? I imagine these move and so might be based on J2000 or something if there are lists. If that's not an option, do you think another appropriate answer to getting a view from "Outside" could be to change any longitude from east to west and vice versa? That should create a mirrored arrangement that is otherwise identical I think?  
> **username_1**: They move very fast!  They go all around the Earth every day. (because the Earth rotates)  
> **username_1**: By construction, on the spring equinox (21st March) the stars with a right ascension of 0h will be above the Prime Meridian at 00:00 UTC.  As one hour is 1/24 of a circle or 15 degrees, stars with a right ascension of 1h will be above the 15 degree meridan and so on. The declension of the stars corresponds directly to latitude, a star with a zero declension will be above the equator etc. So simply reversing longitude may get the effect you want  
> **username_0**: That helps a lot, think I'm getting there now! Just a quick further question if you have a moment. The Wikipedia star entries come with maps that apear to be from an "Outside" perspective, based on your explanation above, am I reading it right? https://en.wikipedia.org/wiki/Delta_Crucis the map goes counter-clockwise in terms of RA.  
> **username_1**: Ah,  but that is looking towards the southern pole, and around the south pole RA goes counter clockwise, and longitude goes clockwise.  So that view of the southern cross is also "looking up"  
> **username_1**: Take a look at https://starinastar.com/earth-map-in-the-sky/  It shows the Earth map projected onto the sky, and as expected, it is mirrored.  
> **username_0**: Thanks, having given that a read I'm not sure I followed all of it, but looking on google earth if I go to the poles I can see that longitude goes from clockwise to anti etc. I'm unsure about what I've created on google earth when I've added star coordinate waypoints to it. On my map if I look at the constellation Crux (useful for having four points in different directions), my Beta Crucis is on the right hand side when looking down at my google earth, but in the map on wikipedia it is on the left of the constellation. Does this mean I've already created the mirror image we are discussing?  
> **username_1**: "Does this mean I've already created the mirror image we are discussing"  Yes  

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