Update docs for calculating window tb

docs/faq.md

@@ -22,15 +22,25 @@ See [Solving](user_guide/phases/solve.md)
 
 ## I have some old data I want to analyze, can I use Spyral?
 
-In general, yes. Spyral has a legacy mode that supports analyzing data taken before AT-TPC's data acquisition was split (pre-FRIBDAQ): see [here](user_guide/phases/point_cloud.md) for more details. However, at this time, it only supports analyzing the ion chamber data out of CoBo 10. Any other auxilary signals will have to be extended or requested.
+If your data was taken in the era where the AT-TPC *did not* have the FRIBDAQ auxiliary
+system, default Spyral will not be able to analyze your data. However, there are some
+projects which have worked to make Spyral compatible with these datasets; see
+[this repo from Zach Serikow](https://github.com/sigmanotation/e20009_analysis).
 
 ## I just ran Spyral and it seems like everything went well, but there is no output data/the results didn't change
 
-Check the log files in your workspace (in the `<your_workspace>/log` directory). Spyral will try to catch-and-continue most errors that aren't directly related to reading the configuration and spawning the processes. This helps us not crash out if one single file out 100 files to be analyzed is not formated correctly, but can sometimes make it look like Spyral ran but didn't do anything. The logs should contain lines indicating if a crash happened and what was detected as a possible error.
+Check the log files in your workspace (in the `<your_workspace>/log` directory). Spyral 
+will try to catch-and-continue most errors that aren't directly related to reading the 
+configuration and spawning the processes. This helps us not crash out if one single 
+file out 100 files to be analyzed is not formated correctly, but can sometimes make it 
+look like Spyral ran but didn't do anything. The logs should contain lines indicating 
+if a crash happened and what was detected as a possible error.
 
 ## I am using Linux and Spyral crashes when I try to use more than one or two processes
 
-This is most likely related to [this issue](https://github.com/ATTPC/Spyral/issues/135). You can modify your script with the following edit
+This is most likely related to 
+[this issue](https://github.com/ATTPC/Spyral/issues/135). You can modify your script 
+with the following edit
 
 ```python
 
@@ -43,4 +53,15 @@ if name == 'main':
     main()
 ```
 
-This is due to a known issue with multiprocessing and some versions of OpenBLAS, where the processor affinity is overriden by OpenBLAS.
+This is due to a known issue with multiprocessing and some versions of OpenBLAS, where 
+the processor affinity is overriden by OpenBLAS.
+
+## My experiment did not measure the window time, how do I calibrate my point clouds?
+
+Spyral provides a function [`calculate_window_time`](api/core/config.md)
+which can be used to calculate the window time bucket from a known drift velocity, 
+GETDAQ sampling frequency, and micromegas time bucket. To import this function use:
+
+```python
+from attpc_spyral import calculate_window_time
+```