TOA150 with TC14A

Camera: Canon 5D2

Telescope: TAK TOA150 with 67 flattener, with and without Nikon TC 14A 1.4x extender

Result:

Without TC14A, star FWHM is about 2.5 pixels.

With TC14A, it becomes 3.5-4 pixels.

The angular resolution with and without TC14A is quite comparable. There is a hint that it is slightly better without TC14A but that can easily be attributed to difference in weather condition.

On the other hand, there is clear lateral color when TC14A is used and weak astigmatism.

To conclude, the advantage of using TC14A is unproven.