... and still the best wife I could wish for!
150mm MCT f/13, 31% CO
"People say I'm in denial. I disagree."
Quote: Edit: Initially, it looks like you might have some degree of undercorrection, or possibly a zone near the edge.
Quote:I just don't understand how it is different from primary SA and if it impacts performance in any different way. As you were saying, the pattern is very different than primary SA.
Quote:...is HSA something that is always localized to the center?
Quote: I just don't understand how it is different from primary SA and if it impacts performance in any different way
Quote:While both are forms of spherical abberation, the differnce between LSA and HSA...
The Obstrucion minimizes the presence of HSA duruing ths star test.
But HSA lowers contrast for larger areas of the target than LSA does, and that was your question.
Here is a simulation that shows how LSA differs from HSA.
Quote:I believe I'm seeing over-correction...
...understanding that LSA may be correctable by adjusting the spacing of the elements to bring things closer to neutral. I have the impression that this isn't something that could be done for HSA.
Quote:Hi All,I need some help with a star test result I am seeing with my 6" F10 IStar achromat.First off, is it even possible to get any meaningful info out of the test if a narrow band green filter is NOT used (ie. Baader Solar Continuum)? The test was in white light only.
Quote: The star test is notoriously hard to interpret accurately
Quote: Quote: The star test is notoriously hard to interpret accurately Using the full range of tests (and there are several) combined with Suiters images, and complimented with Aberrator 3.0, one can get a pretty good estimation of optical quality regardless of the kind of scope being tested.I would still encourage the OP to do the breakout test. If the test shows lower order spherical abberation, then that is ususally the more severe error, and he will know it.If there is no lower order SA and the HSA is below .4, then the scope is bascially diffraction limited.