Haven't used my 152 in MONTHS, so I have it set up now. Gonna repeat star tests, and test some new uber-cheap 2" eyepieces. The lens is cleaned & collimated -- so no alibis!
What I saw... I started right after sunset (clouds on the way!) ~ 2330Z
First star test was on Altair in 7/10 seeing. With a UO HD 9mm Ortho, IF showed a round Airy disk with very bright center / bright 1st ring / much fainter 2nd ring, and outer rings were fainter & tougher to distinguish; OF showed a fainter center, faint 1st ring, very faint 2nd, and outer rings were out-of-round. To save my neck, I put the Baader prism in, and got the same results as straight through,
Second test was on Vega in 8/10 seeing. I used the UO HD 6mm Ortho. I got similar results to Altair, EXCEPT at OF, the center had a green tint. I switched to my spectros PL7.5, and got a cleaner picture both sides of focus, and no green. At focus, I didn't see the "blue halo" that I've seen before in this scope.
Thomas, maybe I missed it, but did you do any straight-through (no diagonal) star tests?
Also: Did APM / Markus say they did a star test on your 152 before shipping it?
It's been posted in this thread & others that the APM 152 & S-W 150 push a lot of limits to stay economical: Cheaper ED glasses, steep curves that must be aligned to tight tolerances, and must stay aligned for shipping globally, etc. The lab report on mine is toward the bottom of the range, and it is by no means a perfect doublet -- I have 50+ year old Japan-made achromatics with better DPAC patterns -- but it performs better than expected. It's like a compact 6" F15.
I hope the replacement is acceptable. Maybe APM has come up against that other limit -- profitability -- and is shipping whatever they have on hand.
Edited by Bomber Bob, 10 November 2019 - 10:52 PM.