I've owned an Espirit 120 refractor since mid-2016, about a year after I purchased it I decided to perform a series of Roddier tests to evaluate the optics.
One immediate finding was the apparent sensitivity of Roddier to seeing conditions, on two separate nights the software reported (in green light) a P-to-V of lambda 3.3 and lambda 4.4, strehls were reported up to 0.924. So, I concluded the lens was diffraction limited but results weren't reproducible. I've attached below the outside focus OF and inside focus IF images taken during one Roddier test. Of course I was hoping to see smooth, nearly identical images. But, there's a small central zone and a fainter ring zone at about half radius.
Given the lack of reproducible results, I am wondering if anyone with more experience in interpreting star tests could comment on the probable effect of these imperfections? Visually, the scope performs fairly well on Jupiter under average sky conditions here which is my acid test for quality, it reveals details that are marginally ahead of my 4 inchers. Maybe I'm expecting too much from a 4.7 inch aperture, however Espirits generally receive rave reviews so this could be a mediocre example of the line.
Edited by Loren Toole, 15 April 2019 - 10:19 PM.