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With low power (e.g. deep sky wide fields) the difference between a $300 achro and a $1000+ ED or $2000+ APO is negligible.
But with high power for planets, there is a difference.
An ED or APO has less (or an APO almost no) color errors appearing as blue fringes around the planet's sphere.
I have a 110mm ED f/7 Chinascope which performs decently on planets at 180x.
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