Explanation/Usage of 瞬きしては

Question

Could it become 瞬【まばた】いている? Why is there 瞬きする instead of 瞬く? And why is there a は at the end?

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Sentence from the song キラキラ星【ぼし】:

きらきらひかる　おそらのほしよ

まばたきしては　みんなをみてる

きらきらひかる　おそらのほしよ

Answer 1

「[瞬]{まばた}く」 is a fairly "big" word and it would sound too heavy or literary to use in a children's song. The more common and intuitive word choice for native speakers would be 「瞬き（を）する」 not only for children but also for adults as well.

「まばたきしては　みんなをみてる」 is in the structure:

「A（を）してはB（を）する」= "to do A and B alternately"

= "(The stars) keep blinking and looking at us all."

See Definition #3 here: http://dictionary.goo.ne.jp/leaf/jn2/152199/m0u/

「は」 is part of the expression and it cannot be omitted.