Hi Jim: Here's the deal: 50X-60X per inch of aperture is the accepted maximum useful magnification for any telescope. At these powers, small details approach the diffraction-limit for any given aperture. Excellent optics will allow a coherent image above that limit, but no additional detail will be seen, since the resolving power of the telescope has already been taken to it's limit. The image can get bigger, but you won't pick up further details. 853X is too high for a 12", you won't see any additional detail beyond that seen at 600X. Make sense? Chuck --- Jim Gibson <xajax99@yahoo.com> wrote:

Question for Rich Tenny (or anyone else)

I saw the new Televue products (41mm eyepiece etc) you mentioned last night at SLAS at:

http://www.televue.com/WSP2003/NewProdsJan2003/New_at_WSP2003.htm

I don’t currently have any hi-power stuff like the 3.5mm or the 2.5mm Nagler. I ran this little program at: http://www.csgnetwork.com/telescopemagcalc.html for a 12” mirror with an f7 focal length and a 2.5mm eyepiece. One of the calculations states that for this setup the “Maximum Useful Magnification” is 600x; however, the 2.5mm would provide 853x. I also recall from a previous conversation we had that someone told you in reference to the Mars opposition that it could take all of the power you could crank. How does all this square? Does the Maximum Useful Magnification mean that everything over 600x (in this case) will go soft? If (big if) I bought a 2.5mm Nagler, could I use it for anything else? I am thinking that such power would only be good for bright planets.

Jim Gibson

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