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Hey J,
You wanting to make one or buy one?
First there is the JOnes Focal corrector spot diagrammes on axis and off-axis are quite a lot larger than the Airy disc. Improvement was made with the Brixner focal corrector where the spot diagrammes are great for red and blue light, but the green suffers bad aberration at 20mm off axis.
When the Jones-Bird came along, it is air spaced doublet, the spot diagrammes were reduced to within the Airy disc for on-axis, but spread out to 20 times the size only 10mm off axis. Axial colour on the J-B is good, but suffers from astigmatism and field curvature.
You could use this telescope quite well for planetary views and some stellar views, after all the eye can accommodate some aberration.
A combination of Erfle eyepieces and the J-B telescope works well as the eyepiece corrects some fo the aberrations present (see Telescope Optics by Harry Rutten & Martin van Venrooij).
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