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Not sure what people are referring to when they say the lens has a turned down edge. Is it the graph that shows the line falling heavily just before the edges of the graph?
Visually there is turned down edge. Of course the lens sits in a cell several mm so any far edge is not even exposed to light. So no issue.
It looks no different to any other high scope I have had like Taks, AP and TEC's. In fact it looks superb and the coatings are very even and a lovely bluish colour. Like an AP.
Oil spaced triplets only have 2 air to glass surfaces which is why they do them this way. They also cool down faster and are less prone to focus shift from temp drops as a large air spaced scope does. Its interesting AP have only done an air spaced triplet once that I know of - the AP160 and I have heard it wasn't as good a scope as the AP155 due to these issues of cooldown and temp focus shift etc. The 130GTX has 1 air space so it must give an extra element of improvement to bother.
TEC only make oil spaced triplets.
A turned down edge refers more to mirrors where depending on how the mirror is mounted the mirrored light surface goes all the way to the edge so a turned down edge would require masking as there is no lens cell to cover that edge and it can lead to a weakness in the image.
Anyway all this is hypothetical and the proof of the pudding will be in the imaging. The camera is a known quantity for me.
Greg.
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