A Mak-Newton is not coma free but the coma is much less than a Newtonian of identical f/ratio. The amount of leftover coma depends on the specific design of the telescope. To get rid of the leftover coma, as well as of field curvature, it is apparently rather simple to design a corrector (because there isn't a lot to correct), the problem being that none is available commercially (the market is too tiny, and it would need to be taylored to a specific MN model, unlike coma correctors for newts).
So if one compares a MN with a newt+good coma corrector, the latter probably wins in terms of field correction but one needs to compare spot diagrams to be sure.
The skywatcher MN190 theoretical analysis is there: https://www.telescop...scopes.htm#most The conclusion being that coma is equivalent to an f/9 newt. Televue says of the Paracorr type II: "This new Paracorr Type-2 inserted into an f/3 Dobsonian made the stars appear as coma-free as a native f/12 mirror."
A MN has some practical drawbacks, it is harder to collimate (two active optical surfaces rather than two), sensitive to dew and takes longer to equlibrate.
But being spike-less is priceless for some
Edited by Dan_I, 02 October 2023 - 11:25 AM.