Interesting on the APM site still having "Lanthanum coated" on the 152ed with 2.5 inch focuser. The text in the listed product for the 152ed with the 3.7 inch focuser has the corrected text. I guess APM only corrected it on the 3.7 inch version. I will drop Markus an email about it as i have to ask him about another product question.
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Maybe "lanthanum coated element" simply means it is a lanthanum element that is coated?