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There is one more thing to understand about Newts, and it has to do with coma correctors. Newts come in a variety of f/ratios, just like every other scope design. What this means is not just a photographic ratio, but describes how deep the focal plane shape is. The faster the f/ratio, the deeper the focal plane. How deep the focal plane is will also dictate how well the EP is matched to its specific shape, convex or concave. So even with EPs designed for a convex focal plane, a particular line will perform better in slower refractors than in faster ones.
What this means for Newts is that Newt specific EPs will show more or less coma depending on the f/ratio, and off course it will be more with faster f/ratios.
How significant coma is as a distracting aberration depends entirely on the individual person. I'll give you my own experience and situation. I have Newts from f/4 to f/5. I only ever use a coma corrector in my f/4 Newt and only with my 30mm 82° eyepiece. Same EP in every other Newt of mine, the eyepiece cleans up the coma really well and I find no need for a coma corrector. A coma corrector is not mandatory in Newts.
What a coma corrector won't do is clean up astigmatism or field curvature. These are different aberrations.
Last edited by mental4astro; 22-01-2019 at 03:56 PM.
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