modifying to remove gala dependence in episodes 1 and 2 and episode functions

Author: abostroem

episodes/02-coords.md

@@ -395,7 +395,7 @@ perpendicular to the direction of the stream (the y-axis in Figure 1).
 These are called the $\phi_1$ and $\phi_2$ coordinates, respectively.
 
 ```python
-from gala.coordinates import GD1Koposov10
+from gd1 import GD1Koposov10
 
 gd1_frame = GD1Koposov10()
 gd1_frame
@@ -405,6 +405,21 @@ gd1_frame
 <GD1Koposov10 Frame>
 ```
 
+:::::::::::::::::::::::::::::::::::::::::  callout
+
+## GD1Koposov10 import
+
+The `GD1Koposov10` reference frame is part of the `gala` package. For convience we provide 
+the stand alone file as part of the `student_download` zip file you downloaded. If your notebook 
+is not in your `student_download` directory, you will need to add the following before the import
+statement
+```python
+import sys
+sys.path.append(<path to student_download>)
+```
+Where `<path to student_download>` is the path to your `student_download` directory ending with `student_download`.
+::::::::::::::::::::::::::::::::::::::::::::::::::
+
 We can use it to find the coordinates of Betelgeuse in the GD-1 frame,
 like this:
 

episodes/03-transform.md

@@ -63,17 +63,21 @@ Whether you are working from a new notebook or coming back from a checkpoint,
 reloading the data will save you from having to run the query again.
 
 If you are starting this episode here or starting this episode in a new notebook,
-you will need to run the following lines of code.
+you will need to run the following lines of code. The last two lines of the import
+statements assume your notebook is being run in the `student_download` directory. 
+If you are running it from a different directory you will need to add the path using 
+`sys.path.append(<path to student download>)` where `<path to student_download>` is 
+the path to your `student_download` directory ending with `student_download`.
 
 This imports previously imported functions:
 
 ```python
 import astropy.units as u
 from astropy.coordinates import SkyCoord
-from gala.coordinates import GD1Koposov10
 from astropy.table import Table
 
 from episode_functions import *
+from gd1 import GD1Koposov10
 ```
 
 The following code loads in the data (instructions for downloading data can be

student_download/episode_functions.py

@@ -7,7 +7,8 @@
 
 import astropy.units as u
 from astropy.coordinates import SkyCoord
-from gala.coordinates import GD1Koposov10, reflex_correct
+from gd1 import GD1Koposov10
+from reflex import reflex_correct
 
 ##########################
 # Episode 2