Kanji meaning inquiry

[athenaltena]

In the interest of finding kanji that phonetically spell out my last name for kendo (in which a person has the option of having their name spelled out in kanji in official tournaments and on their armor) and I'd like to know what these two characters together mean, just to make sure it doesn't mean anything bad. Phonetically they sound out as "Karahan" the approximate transliteration of "Callahan" and are made of the characters for "Sky" (also can mean empty) and "Sort." Any quick feedback from Japanese speakers would be greatly appreciated, as I was told to check the meaning before deciding on one.



Edit: A different version based on suggestions, just to make sure I didn't mess anything up again, using the same first symbol as before and replacing the second with "half"