Microscope Eyepiece Reticle Walton/Beckett 5-1 Ratio for Asbestos Analysis/Counting with calibration factor of 4 for use with 40X objectives.

Available in the following sizes:

• 16mm
• 19mm
• 20.4mm
• 21mm
• 23mm
• 24mm
• 24.5mm
• 25mm
• 26mm
• 27mm

Information

The Walton and Beckett graticule is used for counting fibrous dust (e.g. asbestos or glass fibres) and is particularly useful where the majority of fibres to be counted are shorter than 5 micron. The circle is divided into four by two diametrical lines scaled in units of 5 and 3 microns respectively. 3 and 5 microns are the critical measurements of fibre lengths used in fibre counting. Unlike the usual globes of other particle graticules the Walton and Beckett has a series of shapes to compare objects with. These shapes have been designed for comparison with fibres, especially since they incorporate an aspect ratio of 3:1 or 5:1 essential for such analysis.

IMPORTANT NOTE. The circle on these Walton & Beckett reticles must represent 100 microns at the stage and each one must be manufactured to suit the individual instrument. Therefore, details should be provided with your order of :- Calibration factor, if known or Objective magnification, eyepiece magnification, diameter of reticle disc required, microscope make and model. All Walton & Beckett reticles are normally used with 40x objectives giving a calibration factor of 4. In some microscopes there is also an additional 1.25x magnification to give a total objective magnification of 50x - these will have a calibration factor of 5. All standard Walton & Beckett reticles are supplied with a calibration factor of 4. Other calibration factors are made to special order. These reticles will require a calibrated stage micrometer to verify the sizes

A reticle is inserted into a 'reticle receptive' microscope eyepiece.  The diameter of the reticle is critical and is different for each make and model of eyepiece, each manufacturer of microscopes uses numerous different eyepieces with different diameters. 

Not all eyepieces can take reticles and some need additional reticle support rings to be fitted. 

Ideally the reticle should be fitted into a special 'focussing/adjustable' eyepiece which, when removed from the microscope eyepiece tube, can be adjusted in length.  This is not the same as eyepiece tube diopter adjustment which is irrelevant.  The purpose of the adjustable eyepiece is to ensure that the image in the reticle is definitely in focus when observing you subject under the microscope.

Only the manufacturer can advise you which size you require, we are unable to advise you which size to purchase unless the microscope was purchased from Cambridge Optics or one of our related businesses such as Ultramacro Ltd.

The reticles we are listing here are not from the microscope manufacturers but are from the principle factory who supply most microscope manufacturers and are of equivalent quality at a much lower price.  Not all reticles listed are held in UK stock and some are only available when sufficient quantities for a batch have been accumulated, therefore occasionally we may have to advise you that there will be a significant delay in supplying the reticle.

Please note that because there are over 600 different types and sizes of reticles available (only a fraction of which are listed here), if there is anything specific you need that you cannot find or if you would prefer a reticle from a specific microscope supplier we can obtain it for you, please enquire.

We regret that because each reticle is essentially a 'rare' part, with little prospect of us being able to resell it in the short term and because they are specially cleaned and sealed prior to shipment, we are unable to accept any returns.