NavList:

   

Reply

Noell,
Your computation looks correct to me, but take into account that
your telescope will probably have lower quality than a factory made one.
They usually use the eyepiece consisting of several lenses, to remove the
chromatic aberration. One-lens eyepiece will probably have somewhat
lower quality of the image.

Alex.

> The "outside in the sun" folks were correct. the focal length of the
> objective lens is 150 mm and Yes, I wear glasses. After thinking all of
> this through, I sketched out and attached where I think I am.
> 3 X erect scope.
> 150 mm focal length of the objective lens.
> 110 length of the main body of the scope.
> The eyepiece lens should have a focal length of about -50 mm.
> The lenses should be arranged with the 150 - 50 or about 100 mm apart.
> At the 100 mm mark, the rays from the objective lens will be about 6 mm
> across.
> The eyepiece holder/sliding tube has a 7 mm aperture towards the objective
> lens.
> The best choices from Surplus Shed seems to be a DCV (Double Concave) lens
> of 10.9 mm x -52 or a 6.77 x -49.  There are ACH (Achromatic) lenses
> available of 9.5 x -49 and 7.0 x -45.  The ACH 9.5 x -49 seems like the
> best choice.  For $4 to $7 each, I'll probably get an assortment.
>
> Comments are welcome.
> Regards, Noell
> ----------------------------------------------------------------
> NavList message boards and member settings: www.fer3.com/NavList
> Members may optionally receive posts by email.
> To cancel email delivery, send a message to NoMail[at]fer3.com
> ----------------------------------------------------------------
>
> Attached File: http://fer3.com/arc/imgx/Lens-choices-for-3X-erect-sc.pdf
>
>
> : http://fer3.com/arc/m2.aspx?i=125861
>
>
>
>

   

Reply