Do you have any photos taken so we can see the coma?
Flatteners have a spacing they need to be set to in order to correct for coma to the corners.
How were you measuring the coma? Was it imaging or visual?
What size focuser? What camera?
As you can see there are several variables here.
Even though its a refractor its possible that it is out of collimation. TOA optics I believe are quite exact in their spacing and collimation.
Greg.
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