Telescope Reviews: ES14 v.s. Ethos 13

Thanks Tammy, that was an interesting read.

A few things I happened to notice:

In one sentence Daniel apparently equates field flatness with pincushion, rather than a curved field. This is a rather curious misstatement. I think he may want to either rephrase or brush up on his understanding of rectilinear distortion a bit. I agree that rectilinear distortion is much easier to spot in the daytime because of the preponderance of straight line daytime targets - trees, cars, fences, etc, but I'm not aware of any method by which it would actually be reduced at night - however, it would be far, far less noticeable.

As an aside while checking his statement on pincushion in the ES14 I'll note that I felt there was a more pincushion in the ES than the Ethos (so much that it got me wondering just how similar or dissimilar the designs actually are), but I was looking through it during the day at NEAF and I didn't have an Ethos immediately at hand.

I also think he's misidentifying kidney beaning. He might want to take a closer look at the difference between spherical aberration of the exit pupil and blackouts caused by improper eye placement. Given the fact that he's not complained about kidney beaning during the day, I suspect he's actually vignetting the exit pupil by improper eye placement.

Another thing I read with interest was, as Daniel noted, this is still a production sample, not an actual shipped product. I've seen areas where the two ultimately differed in significant ways (both good and bad). It will be interesting to see if there are any differences in the first production batch.

Finally, I also think he should have tested them in fast flat field scopes - something like the NP127, NP101 or an FSQ - from a design standpoint those present, quite possibly the cleanest fields to the focal plane of any scope around and are the best way to separate scope aberrations from eyepiece aberrations. In determining field curvature for example, it could be critical. One eyepiece may have the same direction of curvature as the telescope and have an additive effect, and the other may curve against the telescope's field (subtractive) and actually serve to help correct it.

Overall, an entertaining read - thank you for posting it on the forums, and thanks to Daniel for writing it up. I'm looking forward to hearing more reports from other observers and actually seeing one myself at some point.

T