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Add option to project separation onto an ellipse #1012
Description
Right now separation only gives the angle between two points. Another common "separation" in astronomy is the distance projected along a particular axis (e.g. the major axis of a galaxy). This would be particularly useful because of the rather sordid history of various people confusing which way a PA goes ("degrees east of north" I think is the most common convention).
Also useful (at least in galaxy contexts) might be an "elliptical" distance (where the separation along the major and minor axes is weighted by the ellipticity).
This should probably await until some of the significant coordinate internal changes are done, so I'm not targeting a particular milestone.
Activity
balbinot commentedon Feb 26, 2014
Well I need exactly this for my research. I have a working code to do this (all conventions taken to account). I can try to contribute.
Do you think the coordinates API is mature enough to receive this addition?
eteq commentedon Mar 25, 2014
@balbinot - the general API for defining coordinates will be changing in the upcoming version, but this part of it (separations) probably will not be. So contributing your code is definitely worthwhile - we will then be able to adapt it to the new scheme as we make the changes to the existing
separationstuff.[-]Add option to project `separation` onto a particular PA or ellipse[/-][+]Add option to project `separation` onto an ellipse[/+]eteq commentedon Jul 11, 2014
Note that this was partially implemented in #2487, which did the circular/PA version. However, it would still be useful to add the "ellipse" part. So I've renamed this issue appropriately.
I've also tagged this effort-low/package-novice, as it's fairly straightforward either as an extra keyword to
position_angleor as a new method to be called something likeelliptical_pa.smeyerre commentedon Feb 9, 2017
Hi @eteq, I was looking for something I could start on for a "first issue" and I thought I'd try this if it's still open. I just had a clarification question: I assume by "separation along the major and minor axes" you mean the distance projected along those axes. My question is: how should that be 'weighted' by the ellipticity? What's the weight function?
Himanshu-Garg commentedon Mar 19, 2019
is this still open?
interested in giving it a try
Add an additional method and test to calculate the projected distance…
Akshatb2006 commentedon Jan 31, 2025
Hi, I came across this issue and would love to work on it. Could you confirm if this is still available and assign it to me?
Thanks!
neutrinoceros commentedon Jan 31, 2025
@Akshatb2006 we do not usually assign issues, but do feel free to work on it !
mhvk commentedon Jan 31, 2025
@Akshatb2006 - definitely fine to go for it, but do please make sure you are clear about what is desired. I read this issue quickly just because it was high on the 'sorted-by-most-recently-updated' list, but I didn't really understand the goal...
Akshatb2006 commentedon Feb 2, 2025
@neutrinoceros
@mhvk
I’ve submitted a pull request for the feature described in Issue #1012: "Add option to project separation onto an ellipse".
Please feel free to review the implementation. Looking forward to your feedback!
Thanks!
mhvk commentedon Feb 2, 2025
@Akshatb2006 - since @eteq proposed this change, I think best would be for him to review first (I asked in the PR). As I wrote above, I'm not sure what exactly the goal was...
Pittu-Sharma commentedon Feb 13, 2026
Hello, I would like to contribute to this issue. Would it be possible to assign it to me
LoveChauhan-18 commentedon Feb 13, 2026
Hi, I’m interested in working on this issue. Could you please assign it to me?