refractor star test question

What does it mean when inside focus you get nice circles and outside focus it's all blurry. It doesn't seem to effect the view any...

Thanks

Mark

Almost sounds like a turned edge. But that's not very common in refractors since the objective is hidden at the edges by the lens cell. What's the brightness of the outer ring like inside focus?

Try testing with green filter. Going out of focus brings you closer to red/blue/violet foci (while green/yellow disperses), and it usually more or less ruins pattern clarity with achromats.