BS ISO 14490-4 pdf download – Optics and optical instruments – – Test methods for telescopic systems – Part 4: Test methods for astronomical telescopes.
C) Using a piece of ground glass let diffuse light be incident on the eyepiece side of the telescope or the finder telescope, and measure the minimum value of the aperture of the objective by using a travelling miuoscope paralel to the optical axis In object space, which can be moved across the diameter of the objective.
4.2 Focal lengths of objective and eyepiece
The test methods for the focal lengths of objective and eyepiece shall be as given In 4.2.1 or 4.2.2.
4.21 Focal length of objective lens and eyepiece (nodal slide method)
Refer to Figure 1. Anange the rotary table (Item 8 in Figure 1) (nodal slide stand), so that the axis of rotation is perpendicular to the optical axis of the collimator lens (item 3) on an optical bench (item 6). Place a reticle (item 2) at the focal plane ot the collimator. On the rotary table, a slide stand (item 7) is moving in the direction of the optical axis of the microscope (item 5). which has its optical axis approximately coinciding with that of the collimator. Measure the focal length fin accordance with 4.2.1.1104.2.1.3.
4.2.1.1 Install the alignment reticle (item 4 in Figure 1) on the slide stand (item 7) so that the alignment ref ide (item 4) coincides with the axis of the rotation of the rotary table (item 8), as shown in Figure 1 a). While aiusting the microscope (Item 5) so that the reticle (Item 4) can be seen clearly, read out the position of the microscope on the optical bench (item 6) and stop when the position of the reticie (item 4) is such that, when it is slightly rotated about its vertical axis, there is no lateral movement of the image.
42.12 Remove the alignment reticle (item 4) and mount the objective lens (item 9) under test on the slide stand (Item 7) it front of the collimator. Adjust the microscope (item 5) until the sharp image of the collimator reticle (item 2) formed by the lens under test can be seen clearly. Set the rear nodal plane of the lens under test to coincide with the axis of rotation of the rotary table (item 8), as shown in Figure 1 b). i.e. when the rotary table is slightly rotated about its verlical axis, the image of the collimator reticle is stationary. Read out the new position of the microscope on the optical bench.
4.2.1.3 The equivalent focal length I of the objective lens to be measured Is the difference between the positions of the microscope In 4.2.1.1 and 4.2.1.2.
5 Test report
A test report shall be presented including the test results and the ollowing information:
a) test method;
b) date of test;
c) identilication of the test specimen;
d) detals about the test arrangement and/or procedure, if required and/or it iterent from those specified in
this part of ISO 14490;
e) reference to this part of ISO 14490, i.e. IsO 14490-4:2005;
f) name of the test laboratory;
g) name of the examiner.
BS ISO 14490-4 pdf download – Optics and optical instruments – – Test methods for telescopic systems – Part 4: Test methods for astronomical telescopes
