Re: ATM ? about interpreting thickness

[Rick Scott <rmscott@home.com>]

The thickness for lenses is for a solid lens with no holes in the center. It
is measured at the center the optical axis.

D1 is the thickness of the first lens.
D2 is the spacing between the first and second lens.
D3 is the thickness for the second lens.

The thickness of the lenses for the Houghton design is non critical and is
based on how thin or thick you feel comfortable in making the lenses.
Because of this, you won't find any equations for the thickness of the
lenses for this telescope type.

D4 is the spacing from the rear of the second lens to the center of the
primary mirror.
D5 is the spacing from the center of the primary mirror to the center of the
secondary mirror.

R1 is the radius of curvature of the front surface of the first lens.
R2 is the radius of curvature of the back surface of the first lens.

R3 is the radius of curvature of the front surface of the second lens.
R4 is the radius of curvature of the back surface of the second lens.

R5 is the radius of curvature of the front surface of the primary mirror.

Rick Scott
rmscott@home.net
http://members.home.net/rmscott


Mel Bartels wrote:

> Could someone enlighten me?  TIA
>
> MEL:
>          I APOLOGIZE FOR KEEP BOTHERING YOU ABOUT THIS SUBJECT. THE WAY
> I
>      SEE IT, THE THICKNESSES IN THE TABLE OF THE HOUGHTON TELESCOPE (AND
>
>      MANY OTHER ARTICLES IN THE JOURNAL) DO NOT REPRESENT THE PHYSICAL,
>      TANGIBLE THICKNESS OF THE GLASS. I GUESS -AND THAT IS MY QUESTION-
>      THAT THE NUMBER -"D"- IN MILLIMETERS CALLED THICKNESS MAY HAVE
>      SOMETHING TO DO WITH BOTH THE DISTANCES BETWEEN OPTICAL COMPONENTS
> AND
>      THEIR OWN THICKNESS, BUT I DON'T KNOW HOW TO READ THEM.
>
>      THE HOUGHTON EXAMPLE:
>
>                 RADII OF CURVATURE              THICKNESSES
>
>                 R1  1286.81                     D1   16
>                 R2 -4810.34                     D2    3
>                 R3 -1286.81                     D2   12
>                 R4  4810.34                     D4  617.67
>                 R5 -1590.97                     D5 -793.84
>
>      THERE MUST BE FORMULAS INVOLVING RADII, RELATIVE DISTANCES AND REAL
>
>      THICKNESSES TO GET THESE "D" NUMBERS. RELATIONSHIP I FRANKLY DO NOT
>
>      KNOW AND TRY TO FIND OUT.
>
>      THANKS AGAIN AND BEST REGARDS, JORGE.
>
> --
> Clear skies, Mel Bartels
> http://www.efn.org/~mbartels