3D Galactic overview: Need help with angles

General discussion about Celestia that doesn't fit into other forums.
Topic author
Simons Mith
Posts: 6
Joined: 14.10.2018
With us: 5 years 6 months

3D Galactic overview: Need help with angles

Post #1by Simons Mith » 20.03.2021, 14:35

As a side project I thought it might be interesting to use a 3D viewer to display ALL of the stars.dat file contained within an overlay of the 3D shape of the galaxy.
I was going to create the latter by machine-generating a 3D shell of artificial stars, spaced every 100x100 LY (or whatever seems to work). Before I do that I'd like to ensure I'm getting the orientation of the galaxy correct. See attached image.

The outer shell is going to be a sphere of 200000LY diameter. The inner disc will have a diameter of 170000 LY.
I was going to make the central bulge a sphere of 16000LY and the rest of the galaxy a thick disk which has height zero at the galactic edge (85000LY )and 3000LY thick at Sol distance from the center.

Galaxy.art.png


The result will be a huge blob of stars centered around Sol and tailing off with distance, with a few far dots at a few thousand LY, which is the limit of the stars.dat file.

Before I do it, have I got my coordinates right, and are those galactic dimensions reasonable? Any suggested refinements will be gratefully received.

Edit: also, has this already been done? Not AFAICT
Edit 2: The 3D viewer I have handy understands .xyz files, so I do need to make the shell out of dots. Refinements using lines are an obvious possibility, but I'd presume that /has/ already been done.
Last edited by Simons Mith on 03.04.2021, 16:41, edited 1 time in total.

Topic author
Simons Mith
Posts: 6
Joined: 14.10.2018
With us: 5 years 6 months

Post #2by Simons Mith » 22.03.2021, 13:20

Well I reckon if there was something glaringly wrong someone would have at least queried it. I'll go ahead with this info, and share the results in a day or two.

Topic author
Simons Mith
Posts: 6
Joined: 14.10.2018
With us: 5 years 6 months

Post #3by Simons Mith » 01.04.2021, 13:10

OK, there's an angle (or two) I can't find the correct value for. The Sag A* black hole lies in the centre of the galaxy. I had assumed it was on the galactic plane.
Sol is about 50LY above the galactic plane, and about 26673LY from Sag A*, right? So it should be well inside the volume of the main galactic disk.
If you convert distances and angle from Sol-Sag A* into xyz coordinates you get (-1421, -2544, 25837). So the galactic plane needs to be angled correctly so that Sol is placed correctly. But when I use the angles I've got (266.42, -29.01), it's a long way out of the correct position. See image and attached xyz file.
I'm obviously misusing the data here. I assume it's a simple error. Can anyone tell me what the correct values should be?
To view the xyz file I'm using a simple viewer called Blaze 3D 2.7.3 lite, available for free on Steam.
[Edit 2021-04-03 (post title amended)]
Attachments
galaxy.txt
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galaxy.png


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