Quote:
Originally Posted by Wavytone
Petr, for observing the planets, in increasing order of quality:
Short-focus Newtonians (typically f/5 or less) are intended for wide-field imaging, not high magnification. Adding barlows and/or ridiculously short eyepieces is about the worst solution for planetary observing.
(ast Newt = poor choice)
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With respect, this sounds like thinking from 50 - 25 years ago .
In the evolving Newt market a telescope slower than F5 above 12" aperture is a rarity.
Televue Powermate focal extenders do not lose you any optical quality , so provided you keep your obstruction below 20% ( easy for a visual scope) , have good optics , and can keep your scope well collimated F4 to F4.5 , in a medium aperture, a Newt is the preferred choice as they are well ventilated. World renowned planetary imagers like Anthony Wesley and Trevor Barry both use 16" Newts in this focal ratio.
Even if you do not use an extender there are many long eye relief short FL EP's these days that are beyond reproach. There is much more information about collimation these days and low cost superb collimation tools make the job easy.
Mark