Change coordinates when using peek()

[mjm159]

Issue #388

I added some functionality that allows users to change the coordinates by setting the "coords" value to 'HG', 'HPC', or 'HCC' in the peek() method.

[ayshih]

This is more for issue #376, and I see that I neglected to add a comment there about my proof-of-concept commit (ayshih@50cf1ff), which was only discussed on the mailing list.

Unless I'm missing something, your implementation assumes that the native coordinates of the map is helioprojective (HPC) coordinates, but maps could actually be in heliographic (HG) or heliocentric (HCC) coordinates (or more, really, but let's not worry about that right now). You ought to check the coordinate system of the map so that you know which WCS conversions to call.

[fmayer]

Maybe also make it possible to register new coordinate systems a dictionary of sorts.

[mjm159]

@ayshih I tried to include a comment referencing your work, but I don't know where the best place to put it is, so I just included it in the code itself.

You're right, I was making an assumption that the native coordinates are in HPC. Where are the native coordinates determined? I spent a long time looking through the code trying to figure out where the initial coordinate system was set and didn't have much luck. When you wrote your proof of concept, how did you know to put it where you did?

I've heard the dictionary idea before and I actually really like it, and would prefer to use one. I would like to try to work with you guys to develop. Would it be best to make a dictionary of lamda functions?

[mjm159]

Also, I want to apologize for my poorly commented initial commits. I'm still getting the hang of the whole GIT experience :)

[fmayer]

Why is this necessary?

[Cadair]

Am I right in saying that this is assuming the coordinates of the input map is in HPC? If so this needs to be generalised :)

[ehsteve]

This code needs to check that the input coordinate system is HPC as it currently assumes this. Should be good to go after that change!

[mjm159]

I'm closing this pull request until I get a chance to update the code