Celestron Ultimas

I have the 15mm version of the celestron widefield series.A 16 mm version did not exist. The widefield versions were apparently the predecessors of the Axiom series of celestron eyepieces. I find the 15 mm widefield ultima to yield a bright and contrasty image but with coma at the edges.

"I find the 15 mm widefield ultima to yield a bright and contrasty image but with coma at the edges."

That would be astigmatism, not coma.