Quote:
Originally Posted by Shiraz
Newtonian systems produce off axis coma. The standard parabolic mirrors require relatively expensive 3 or 4 element coma correctors to get rid of it without introducing a degree of spherical aberration. Hyperbolic mirrors can be pretty well corrected with 2 element coma correctors, but the main mirrors seem to be more expensive to make.
The results are basically the same for both and the extra glass of a properly made corrector should be no concern.
Explained in http://www.telescope-optics.net/sub_..._corrector.htm
agree with Wavytone that the Maksutov corrected spherical Newtonian systems are a good choice. |
If the result are basically the same than why would someone buy ASA 8 inch Hyperbolic astrograph,which cost fortune, (apart from motorized focuser, which is needed for fast telescope to focus) instead of GSO 10 or 12 inch newtonian with ASA corrector or any other type of corrector for that matter, which would cost way less?
BTW: ASA parabolic astrograph are also costly.
Thanks in advance.