Help with map maths?!

J

Jump 6

Mongoose
Hi everyone,

I’m looking at building a new setting based around near Earth stars, and was hoping that someone may be able to help advising me how to convert Right Ascension and Declination into X, Y, Z Cartesian co-ordinates?

So far, I’ve found methodology here;

https://www.jameswatkins.me/posts/converting-equatorial-to-cartesian.html

…but was hoping someone might know of an online calculator, or a spreadsheet they could share for doing this, to save the heavy maths.


Many thanks
 
Jump 6 said:
Hi everyone,

I’m looking at building a new setting based around near Earth stars, and was hoping that someone may be able to help advising me how to convert Right Ascension and Declination into X, Y, Z Cartesian co-ordinates?

So far, I’ve found methodology here;

https://www.jameswatkins.me/posts/converting-equatorial-to-cartesian.html

…but was hoping someone might know of an online calculator, or a spreadsheet they could share for doing this, to save the heavy maths.


Many thanks
Click to expand...
I had a spreadsheet years ago. Not sure I still have it (HD crash happened). I'll have a look.
 
I don't find this file anymore. Need to check some very old hard drives.
It was close to 2 decades ago. I downloaded the Hipparcos data (hundreds of thousands stars).
X, Y, Z was computed using sin & cosin functions and the distance. I just had to transform the declination in a proper angle.
I may be able to reconstruct the formulas. Just need some time.
 
After some archeology, I found my old file.
Do you already have the stellar data ? If not you should download the hipparcos stellar catalog (There is a more recent one - Tycho-2 Catalogue, but I don't know if you can get it free). You'll have more stars than you can use (118 200).
As for the math, what do you need exactly ?
 
Alqualonde said:
After some archeology, I found my old file.
Do you already have the stellar data ? If not you should download the hipparcos stellar catalog (There is a more recent one - Tycho-2 Catalogue, but I don't know if you can get it free). You'll have more stars than you can use (118 200).
As for the math, what do you need exactly ?
Click to expand...
Thanks, I have some data I found on line, but the one you cited there is probably more accurate, so I shall take a look.

Regarding the maths, it all looks pretty heavy to me, so just wondered if there was an online calculator, or spreadsheet, into which you could just plus in the data and get the coords out...
 
No warrantee, but this excel spreadsheet is based on work almost ten years since I last touched it and probably twenty since it was originally developed, but it's the Excel format I've been using. A few near stars are included, but I would double-check the data as it is also two decades old. The Earth coordinates are the 'simple' answers based on RA DEC and Parallax and computed in light-years (divide each by 3.26 for parsecs).

Then there is a bunch of rotations which I cannot remember the complete details on, but they were based on the direction of galactic north and center at least as known at the start of this century. And out spits the X, Y, Z (in light years) in my version of 'Imperial Coordinates' based on:
+X = Spinward
+Y = Coreward
+Z= North

If this link works:
StarMapSample
 
Jump 6 said:
Hi everyone,

I’m looking at building a new setting based around near Earth stars, and was hoping that someone may be able to help advising me how to convert Right Ascension and Declination into X, Y, Z Cartesian co-ordinates?

So far, I’ve found methodology here;

https://www.jameswatkins.me/posts/converting-equatorial-to-cartesian.html

…but was hoping someone might know of an online calculator, or a spreadsheet they could share for doing this, to save the heavy maths.


Many thanks
Click to expand...
I made a list of the some of the nearest star systems with xyz coordinates, and it was published for free in cepheus journal https://cepheusjournal.com/downloads/list-of-nearest-stars/
 
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