Astrographs vs wide field scopes

I have questions about astrographs as compared to other wide field scopes.

It seems to me that astrographs are extremely expensive compared to other quality wide field scopes. Is there a TRUE advantage to astrographs? Of course I understand that it all depends on the quality and manufacturers but is it really worth paying for astrographs?

How is it compared to celestron with fastar or hyperstar or like telescopes?

Can a newtonian be converted to F2 or F3 without too much coma issues to rival a fast astrographs?

Just some questions I've been pondering and hope that the experts out there can help answer them.

Thank you.

Astrographs are specialty instruments that have been designed to produce a flat field image with no coma and no astigmatism, sometimes also with no distortion (barral or pincushion) and be fully baffled so no off-axis light can reach the focal plane, plus have full or nearly full illumination to the corners of the field. Almost all normal "wide field" scopes have one or more of the above defects. Yes, they can produce nice looking images but when you want edge resolution same as center resolution, then an astrograph (properly designed) is going to be your best bet.

Because of the various requirements listed above, an astrograph will usually not be a good visual instrument. The mirror types will have oversize central obstructions and be generally way too fast for good eyepiece performance. Even the best eyepieces will begin to add significant on-axis spherical and off-axis aberrations to a scope that is faster then F4.

Rolando