# cassegrain telescope magnification formula

If only the very center of the field is fully illuminated (say the central 0.05"), then we should see the reflection of the edge of the primary mirror right at the edge of the secondary mirror. While magnification is really not as important as field of view of aperture, to determine the power of a telescope, simply divide the eyepiece diameter to the telescope focal length: The magnification of any telescope is controlled by the eyepiece being used and can be calculated by dividing the focal length of the telescope by the focal length of the eyepiece. -If you are figuring a Cassegrain secondary using star testing, increasing the correction of the secondary will decrease the correction of the system. Here's a thread on the ATM list that discusses testing a convex hyperbolic secondary through the glass. Magnification of a telescope is actually a relationship between two independent optical systems: the telescope itself and the eyepiece you are using. All that is left is to determine the shape of the primary and secondary mirrors. MAKSUTOV-CASSEGRAIN TELESCOPE. This feature can be manipulated using different combinations of objective and eyepiece lens. The following is a selection that involves telescope magnification. Other terms that need to be defined for future use: With that introduction, here are the important equations for designing the dimensions of a Cassegrain telescope. There are even some files for OSLO-LT (usable in the EDU version as the EDU version is an upgrade and it reads files from earlier versions) that show examples of finding the necessary Conic Constants and other such necessary specifications for the secondary. The second number means that an error of plus (or minus) one millimeter in R2 moves the focal planeda / dR2mm farther from the secondary mirror with a negative number meaning that the distance is closer. "Advanced Telescope Making Techniques, Vol. The telescope’s focal length (for example, 1200mm) 2. If K > 0, we have an oblate spheroid, basically a shape with a shorter radius as you go out in distance from the center rather than a longer distance in the outer zones that you'd have with a hyperboloid, ellipsiod or parabola. Well, when you decrease the spacing between the secondary and primary, the focal length of the system actually gets longer, and this adds dramatically to the sensitivity to spacing changes. The first of these is telescope magnification, and by this I mean angular magnification. Those two variables are dependent on a, B an A, which vary with the location of the secondary mirror. A quick numerical calculation using the mirror spacings for my 12.5" classical Cassegrain indicate that if it were a Dall-Kirkham, then moving the secondary toward the primary would require a slightly less corrected primary. h��V�n�8�>6(���F�ǮS�MjDjS���b����&ߙ�%�i�n�(9w�P2L0K���k�)��ϔ�9`��`�T"!bҗ>�I�[�@~B���ٻw|֔M����ER"�n@֔�Ʉ�����-Z]���;͢�-lf���5�|J���9�e�lRcW|9_��. -If the secondary mirror is moved AWAY from the primary mirror, the correction of the system will INCREASE. %PDF-1.5 %���� Since Ks = -4.00 for the secondary, for example, it is a hyperbola with 4.00 times the correction of a parabola, so if we are to make a concave test plate, we simply multiply all the ideal knife edge displacements by 4.00 to get the proper shape of the secondary.. It was also obtained from ATM Vol 1, A general formula for the shape of a cross section of a mirror's surface is given as a reference by: Basically, the parameter K determines the type of shape a concave or convex mirror has. In order to design a Cassegrain, we need to calculate it according to the type of Cassegrain we wish to make. Telescope Equations Magnification of the Telescope Theory Size and Distance in the Sky. h�b```f``2d`a``;� Ȁ �@1�H6`I4R�8 �I�Q�J��B��>�r�]��,n�x����fE�R���巪�u�k�f���5��D��&���5�w#�kV&��cv��!� ���5�5w;��Ȼ&�Tt40� �����dt40)A�����@!0�� fe;��@*;@J�H����O� ��m�R � �`�p^Ɗ�'�:qh��]��b�ι�!���5��o��4�'oA��^ �d`�|��` ��zW CASSEGRAIN SECONDARY SIZE (C): The most commonly used formula for determining the Cass secondary size has been in "Amateur Telescope Making", Book one in the original format. The eyepiece has a field of view of 52°, so the field of view for the telescope at this magnification will be 52 ÷ 30 = 1.7°. So where does the extra sensitivity come from? Magnification of a telescope is actually a relationship between two independent optical systems: the telescope itself and the eyepiece you are using. Telescope Magnification Formula. To determine power, divide the focal length of the telescope (in mm) by the focal length of the eyepiece (in mm). The first is the shape of the primary which is: Next is to derive the shape for the secondary. For a Cassegrain this means that the secondary mirror must be large enough to allow the entire primary mirror to be "seen" from the parts of the focal plane that we wish to fully illuminate. 0 m = 1 for flat. They can be manipulated as needed to solve for various quantities. The correction of a Cassegrain optical system with an aspheric secondary mirror (classical, R-C) is dependent on the primary-secondary distance.