Difference image example for the gallery

[jmason86]

Description

This is my first gallery example so may have done something wrong, especially with sphinx stuff.

Partially address Issue #3.

[pep8speaks]

Hello @jmason86! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file examples/map/difference_images.py:

Line 65:1: E265 block comment should start with '# '

Comment last updated at 2020-02-05 14:25:43 UTC

[ghost]

Thanks for the pull request @jmason86! Everything looks great!

[Cadair]

Thanks for this @jmason86 it looks great. A few inline comments :)

[jmason86]

Note that there are several impediments to doing this with coronagraph data right now due to other issues. Unfortunately, that's the class of data that probably does the most difference imaging.

For example, Issues:

• a.Sample does not work for VSO for STEREO Data #3331
• Strange key added to map.meta '\x00\x00\x00\x00\x00\x00\x00\x00' #3248
• and (probably a related issue to Strange key added to map.meta '\x00\x00\x00\x00\x00\x00\x00\x00' #3248), trying to plot LASCO at all can cause:

WARNING: SunpyUserWarning: Could not determine coordinate frame from map metadata [sunpy.map.mapbase].

and

ValueError: FITS header values must contain standard printable ASCII characters; 'offset_bias.pro\t1.37, 12/18/14, 631.118V15 18 Jun 1997 MAKE_FITS_HDR2' contains characters not representable in ASCII or non-printable characters.

[Cadair]

Thanks @jmason86 this looks really good. One minor comment 😄

[Cadair]

This should probably be squash merged.

[sunpy-backport]

The backport to 1.0 failed:

Commits ["bc2205adfda2aaacade15ebac7ac53b594b44b12","11956d656e42184395cc53a7e8d23a8715db8a53","feb8509958e54d2664fdbb81a61b8fba273b72b5","00a20db204b81d21ecc586d99b457d1859049f07","574981075b2f495c2dd77067d1f6a7121a68adcf","440c36983f8ba51cef0c4bc3c032b096722e5e82","d1ca1a3fd4b8e5f10e93e0479300fa57ce5a753c","3d891f8c7ed2ff39ae5272706d97fe851c738a6e","f5820c0dbd49b6e52c96dc069c9aa6b4afc7407c","ded490aed9535239e3dc5b129ba1241ead407e86","f228ad4f2eabf012d8047a581719f31b72da1641","6de893a9ebd8c8e6343e5d8d015b6055bec0b12e"] could not be cherry-picked on top of 1.0

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub.
git fetch
# Create new working tree.
git worktree add .worktrees/backport 1.0
# Navigate to the new directory.
cd .worktrees/backport
# Cherry-pick all the commits of this pull request and resolve the likely conflicts.
git cherry-pick bc2205adfda2aaacade15ebac7ac53b594b44b12 11956d656e42184395cc53a7e8d23a8715db8a53 feb8509958e54d2664fdbb81a61b8fba273b72b5 00a20db204b81d21ecc586d99b457d1859049f07 574981075b2f495c2dd77067d1f6a7121a68adcf 440c36983f8ba51cef0c4bc3c032b096722e5e82 d1ca1a3fd4b8e5f10e93e0479300fa57ce5a753c 3d891f8c7ed2ff39ae5272706d97fe851c738a6e f5820c0dbd49b6e52c96dc069c9aa6b4afc7407c ded490aed9535239e3dc5b129ba1241ead407e86 f228ad4f2eabf012d8047a581719f31b72da1641 6de893a9ebd8c8e6343e5d8d015b6055bec0b12e
# Create a new branch with these backported commits.
git checkout -b backport-3627-to-1.0
# Push it to GitHub.
git push --set-upstream origin backport-3627-to-1.0
# Go back to the original working tree.
cd ../..
# Delete the working tree.
git worktree remove .worktrees/backport

Then, create a pull request where the base branch is 1.0 and the compare/head branch is backport-3627-to-1.0.

[sunpy-backport]

The backport to 1.1 failed:

Commits ["bc2205adfda2aaacade15ebac7ac53b594b44b12","11956d656e42184395cc53a7e8d23a8715db8a53","feb8509958e54d2664fdbb81a61b8fba273b72b5","00a20db204b81d21ecc586d99b457d1859049f07","574981075b2f495c2dd77067d1f6a7121a68adcf","440c36983f8ba51cef0c4bc3c032b096722e5e82","d1ca1a3fd4b8e5f10e93e0479300fa57ce5a753c","3d891f8c7ed2ff39ae5272706d97fe851c738a6e","f5820c0dbd49b6e52c96dc069c9aa6b4afc7407c","ded490aed9535239e3dc5b129ba1241ead407e86","f228ad4f2eabf012d8047a581719f31b72da1641","6de893a9ebd8c8e6343e5d8d015b6055bec0b12e"] could not be cherry-picked on top of 1.1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub.
git fetch
# Create new working tree.
git worktree add .worktrees/backport 1.1
# Navigate to the new directory.
cd .worktrees/backport
# Cherry-pick all the commits of this pull request and resolve the likely conflicts.
git cherry-pick bc2205adfda2aaacade15ebac7ac53b594b44b12 11956d656e42184395cc53a7e8d23a8715db8a53 feb8509958e54d2664fdbb81a61b8fba273b72b5 00a20db204b81d21ecc586d99b457d1859049f07 574981075b2f495c2dd77067d1f6a7121a68adcf 440c36983f8ba51cef0c4bc3c032b096722e5e82 d1ca1a3fd4b8e5f10e93e0479300fa57ce5a753c 3d891f8c7ed2ff39ae5272706d97fe851c738a6e f5820c0dbd49b6e52c96dc069c9aa6b4afc7407c ded490aed9535239e3dc5b129ba1241ead407e86 f228ad4f2eabf012d8047a581719f31b72da1641 6de893a9ebd8c8e6343e5d8d015b6055bec0b12e
# Create a new branch with these backported commits.
git checkout -b backport-3627-to-1.1
# Push it to GitHub.
git push --set-upstream origin backport-3627-to-1.1
# Go back to the original working tree.
cd ../..
# Delete the working tree.
git worktree remove .worktrees/backport

Then, create a pull request where the base branch is 1.1 and the compare/head branch is backport-3627-to-1.1.