BS ISO 14490-4 pdf download

BS ISO 14490-4 pdf download Optics and optical instruments — Test methods for telescopic systems — Part 4: Test methods for astronomical telescopes
1 Scope
This part of ISO 1 4490 is applicable to amateur astronomical telescopes.
For general optical test methods of telescopic systems see ISO 1 4490-1 .
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 8596, Ophthalmic optics — Visual acuity testing — Standard optotype and its presentation
ISO 1 41 32-1 :2002, Optics and optical instruments — Vocabulary for telescopic systems — Part 1: General terms and alphabetical indexes of terms in ISO 14132
ISO 1 41 32-4:2002, Optics and optical instruments — Vocabulary for telescopic systems — Part 4: Terms for astronomical telescopes
ISO 1 4490-1 :2005, Optics and optical instruments — Test methods for telescopic systems — Part 1: Test methods for basic characteristics
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 1 41 32-1 and ISO 1 41 32-4 apply.
4 Optical test methods for astronomical telescopes
Typical test methods are shown here, and other similar methods are acceptable.
4.1 Clear aperture of objective
The clear aperture of the objective shall be measured by one of the following methods.
a) Measure the unobstructed diameter of the objective lens of refracting telescopes and finder telescopes or that of the main mirror of reflecting telescopes by means of an appropriate linear measuring instrument.
b) Set the focus of the optical system of the telescope or finder telescope to infinity using a dioptric tester.
Set a bundle of parallel rays at zero incidence angle using a collimator on the eyepiece side, project the exit bundle of rays from the objective onto a screen perpendicular to the optical axis and measure its diameter.
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 microscope parallel 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.
4.2.1 Focal length of objective lens and eyepiece (nodal slide method) Refer to Figure 1 . Arrange 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 of 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 f in accordance with 4.2.1 .1 to 4.2.1 .3.