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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I agree with Rupert and Marciej.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>To demonstrate the working of a telescope, I have used the
following parts:<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>For the objective lens:<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>My reading glasses of +1.5 diopters strength. <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>A diopter is the inverse of the focal length in meters.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Examples: +1.5 diopter is 1/1.5 = 0.667 meters; 2 Diopters is ½ =
0.5 meters; 1 diopter is 1 meter focal length.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Practically the range 1.5 to 2 diopters works very well—manageable
focal length.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>If anyone in the eyewear lens industry can step forward and supply
really cheap (free preferably) lenses it will be much appreciated.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Otherwise teach the kids to strip their parents’ reading
glasses, but do not blame the resulting fight on me.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>For the eyepiece:<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>A small magnifying lens (also a positive lens) works remarkably
well. I use one with a focal length of about 50 mm.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>The combination yields a magnification of about 5 to 10 times—I
have never measured it exactly, but it demonstrates to operation wvery well.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Shorter focal length lenses will obviously magnify more.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>All you need to do is to devise a way to mount these two lenses
at opposite ends of any structure and a means to move them to achieve focus.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Because only simple lenses are used the instrument does suffer
from various abberations, but works better than I imagined at first.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Higher magnification and shorter focal lengths increase the
abberations.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>If any-one is interested in seeing my demo “telescope”
contact me directly on <a href="mailto:johans@firsttech.co.za">johans@firsttech.co.za</a><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>It was built from cardboard and sticky tape as Rupert suggested.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>If you visit Scope-X on 30 may 2009 you can attend my talk where
I use this demo telescope. (<a href="http://www.scopex.co.za/">http://www.scopex.co.za/</a>)<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Regards <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Johan Smit.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<div>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'>
<p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:
"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'> astronet-bounces@mail.saasta.ac.za
[mailto:astronet-bounces@mail.saasta.ac.za] <b>On Behalf Of </b>Maciej
Soltynski<br>
<b>Sent:</b> 11 March 2009 11:09<br>
<b>To:</b> astronet@mail.saasta.ac.za<br>
<b>Subject:</b> Re: [AstroNet] Galileoscope discussion<o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<div>
<p class=MsoNormal><strong><span style='font-size:10.0pt'>I strongly agree with
Rupert. All that is necessary is the objective lens and the eyepiece lens. The
rest should be a project for the kids / educator / interested amateur.</span></strong><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><strong><span style='font-size:10.0pt'>If money is to be
spent for a complete optical system, then surely binoculars should be
considered?</span></strong><o:p></o:p></p>
</div>
<div>
<p class=MsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><strong><span style='font-size:10.0pt'>Maciej</span></strong><o:p></o:p></p>
</div>
<blockquote style='border:none;border-left:solid black 1.5pt;padding:0cm 0cm 0cm 4.0pt;
margin-left:3.75pt;margin-top:5.0pt;margin-right:0cm;margin-bottom:5.0pt'>
<div>
<p class=MsoNormal>....<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal>I think there is far greater reward in being able to
"create" a <br>
telescope then to be handed it on a plate. Not only will kids learn <br>
about technical problems and that they are capable of solving it <br>
themselves but they may be inspired to go further, instead of <br>
believing that every thing comes from some far off land. Give them a <br>
lesson in the alignment of the optics and the only thing not readily <br>
available- the optics.<br>
I am sure their are capable people in this mailing list who could <br>
build a telescope out of some cardboard or sticks and sticky tape! A <br>
tripod can be made from a string hanging from a tree, or three <br>
broomsticks tied together? ...<br>
<br>
Rupert<o:p></o:p></p>
</div>
</blockquote>
</div>
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