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Old 05-06-2015, 10:02 PM
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alpal
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Quote:
Originally Posted by glend View Post
That quote by Gary can cut both ways in its relevance, yes a refractor objective is at the front and exposed to the night air - but so is the corrector plate of a SCT (dew magnets that they are), and are not all refractors equipped with dew shields these days, and they all (refractors) need dew heaters. Newts however, mostly all have fans, and have a long tube that acts as a dew shield, and being open tube do not have cool down issues that SCTs and refractors do (minimal tube currents) and for truss dobs no tube currents at all.

My point is many of these pronouncements can be turned right around by looking at all aspects of the design and performance. There is a thread over on Cloudy Nights called "Are APOs better than Newts" and of course it was stuck in the Reflector forum by a refractor guy looking for a bit of entertainment. That thread has over 300 posts now and shows no sign of dying off. I own both refractors and reflectors and while the refractors are nice, especially on planets, contrasty, no diffraction spikes, etc, they cannot keep up with a good coma corrected newt in the deep sky light gathering category. My closest hybrid scope is my new MN190 Mak-Newt which seems to combine the best of several worlds at a reasonable cost, and while being the equivalent of a 6" APO in performance (at way less $), it cannot give me the deep reach that the 10" imaging newt does. Aperture, as always, is king; and in the analysis of aperture per $, there is nothing that can match a newt. So it comes down to what aspects of performance are important to you, if it's only uncorrected star shape, and contrast then yes a large refractor will get you going, but if your after deep reach then only a reflector can give you that at a cost way less than any larger APO refractor.


Hi Glend,
I Agree & I only use Newts. because I like imaging deep sky targets.
Newts. give the best bang for the buck in that area.

A Schiefspiegler Newtonian telescope would be interesting as there is no obstruction
but I've never looked through one.
There is a good article here on obstruction & design of Newts:

http://www.alpo-astronomy.org/jbeish...Sec_Mirror.pdf


cheers
Allan
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