Rich: I am unfamiliar with the term "Goodwin Mask", so unless I know it by a different term, my comments do not apply to it. Off-aperture masks are not apodizing masks. All they do is turn large, obstructed telescopes into smaller, unobstructed telescopes. Resolution suffers due to aperture reduction, but contrast is increased due to elimination of obstructions. If the seeing will not support the full-aperture of the obstructed scope, using an off-aperture mask is a good idea. Apodizing masks that give spider vanes funky outlines usually do not impart an across-the-board improvement in imagery, and should be used for special purposes only. It is very difficult to remove the psychological factors from such devices. While I have first-hand knowledge of their use, other than channeling diffraction I have never experienced a gain in resolution except in the case of close double stars. And here, understand that the telescope wasn't exactly gaining resolution- it just moved the glare from the brighter star into a position that it didn't swamp the dimmer companion. Dead-on collimation and smooth, accurrate optical surfaces are the best tools for maximizing resolution. Diffraction-modifying devices usually modify contrast. While the two terms describe differrent phenomenon, they are inter-related, especially on extended objects like planets & nebulae. It is now very apparent that different people have different criteria as to what constitutes a "high-quality" view, so I must refrain from an outright "yes" or "no" to your question. Try the mask, and determine for yourself if it helps or hinders your observations. C. --- Richard Tenney <retenney@yahoo.com> wrote:
--- Chuck Hards <chuckhards@yahoo.com> wrote:
It makes no difference if the obstruction is high in the tube, or at the mirror's surface.
Chuck,
Are you saying that unless one is splitting double stars, it is highly unlikely that any increase in image sharpness or quality will be realized with such a mask for planetary viewing? (it's all just imagined, or is simply a result of better collimation)?
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