Telescope Resolution

[rogerinnh]

I have a twelve-inch Dobsonian telescope. Instructions that came with it explains how you can use it to view the Moon (a too-bright object for the full twelve inch aperture) by making an aperture mask for it, which is simply a round, 12-inch diameter piece of cardboard with a three-inch hole in it near the outer edge which is placed over the aperture of the telescope.<br /><br />It is easy to see how this reduces the amount of light entering the telescope, and therefore makes it possible to comfortably view the Moon, but what effect does that aperture mask have on the resolution of the resultant image? Do I then get the resolution of a three-inch telecope, since the aperture is now just three inches, or do I still get the resolution of the full 12-inch telescope, since the surface that the incoming light reflects off of still has the curvature of the twelve inch mirror?

 

[unclefred]

You will get the resolution of a 3 inch telescope. There are other factors like diffraction of the diagonal mirror, how far the aperture is from the primary mirror, how far off axis the aperture is, etc. However all these other factors are minor and can be ignored.

 

[kyle_baron]

A variable polarizing filter, where you can control the amount of light is another option. Orion Telescopes should sell them:<br /><br />www.oriontelescopes.com <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>