So when KStars downloads index files, they are just fits files in a folder. It doesn't do any extra processing to them. You should have files like index-4200-01.fits index-4200-02.fits in your folder. KStars will simply check the folders you tell it to search and checks off the file sets it finds in the index file downloader tab. One issue might be that that particular file set is pretty large and you should make sure they downloaded properly, but that wouldn't affect whether they get checked off in the index file downloader in KStars because that is just based on the file names found in the folder.

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