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Full Version: How do I compare two observing lists?
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Say I want to compare the RASC Finest NGCs with the SAC Best NGCs. Or seasonal lists by different authors. What are the best ways to compare two lists, to see which objects are in both, and which objects are in one but not the other?

One way is to export each list in simple text format, sort each alphabetically then use a compare tool to see the differences (this is why sorting them first was necessary).

On Windows, you can use the built-in sort command in the terminal (also, many text editors have this functionality). For comparison, you can use the spartan terminal command fc or a nice GUI tool like ExamDiff.
For a specific object, you can open the Object Info and then the Observing Lists tab. This will show you every list that you have installed, in which this object appears.

SkyTools is designed more for planning rather than this sort of general list spread sheet stuff, but if you are creative there are ways to do possibly get at you want.

Sorting the lists in designation order might allow you to print (or copy to the clipboard) both lists and then you could compare them easily. This may be the best solution.

You might also be able to leverage the fact that a list can not have the same object in it twice. You could do something like this:

1. Create a new, empty, list

2. Open your first list and reset all the filter so every object is displayed.

3. Right-click on the red check mark column header and select "Check all"

4. Right click on any red check mark and select "Copy all checked to..." and copy all of the objects to your new list. This will make a copy of the first list.

5. Open your new list and check every object as you did before. This will mark every object that is in the first list with a check.

6. Open your second list and follow the same procedure to check every object in it, and then copy the objects to your new list.

When you open your new list any objects that are not checked appear only in the second list. You could right-click in the red check mark column and delete every object that has a check mark. The result would be a list of objects that appear only in the second list. One could imagine doing the same, but reversing the lists such that you would end up with a list of objects that only appear in the first list. I don't know how useful this would be, but it serves as an example of how one might manipulate the lists using the copy function.
i do make use of the Observing Lists tab in Object Info; it is a nice feature that enables manual screening.

I also do the merging of two lists as you (very clearly) describe in your steps. I had not thought of using checks prior to merging as a way to identify the new unique items. That will be a real timesaver. And as you say, I can do it twice, once to find what is in both A and B, and in B but not A, and once again for A but not B.