# Strange spectral types in star catalogs

I'm collecting different star catalogs I've found in the Internet to make my own and I noticed some "strange" peculiarity in how those catalogs describe spectral type of a star.

Namely:

• sometimes the type has got a slash like "G8/K0III". Does it mean it is a binary star system? A variable star? A measurement uncertainty?
• other types has an ellipsis: "K0...". This one is a completely mystery to me...
• you can find even "+" and ":"
• and the last but not least: plain weird names like "K1IIICN..."

May someone explain where those enigmatic descriptions come from? What in the way a spectral type is determined in observatories makes the need of such things?

Wikipedia has a pretty comprehensive list of all these peculiarities and their meaning. Spectral classification also is not always unique or unambiguous.

• "/" denotes stars which could be classified as either
• "..." denotes undescribed peculiarities
• "+" denotes hypergiants. But see there also for deviating use of "f+" or "(f+)".
• ":" denotes uncertain spectral classification
• C,N,O, (any element symbol) denotes particularily strong lines from that element(s)

That said, any catalogue might want to explain uncommon nomenclature in its notes.