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| Beck microscope thing ? |
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| Pete W.:
Hi there, Rob, (I've just had a message that three other replies have been posted while I was composing this - apologies if I've duplicated info.) Your instrument looks like a two-axis travelling or vernier microscope. At first glance, it looks to be in excellent condition. It isn't a model I recognise but Beck's speciality was making custom instruments to the customer's specification. (They had some carefully worded clauses in their guarantees so they could accept the business but avoid complaints if the client's ideas were too outlandish!) I have a Beck catalogue or two somewhere here - I'll dig them out and see if they do show anything like the one in your photos. Please forgive me if any of the following is 'teaching Grannie how to suck eggs'. There should be engraving on the eyepiece and on the objective. The eyepiece engraving just gives its magnification, could be as low as x3 up to as high as x20. My habitual eyepieces are x10. The engraving on the objective will probably be like this: 10/0.25 and 160/0.17 The first pair are the magnification and the 'numerical aperture', the second pair are the mechanical tube length (in mm) and the thickness of the cover slip (assuming that it's going to be used with a conventional slide-mounted specimen. Low magnification objectives aren't usually too fussy about cover-slip thickness so they're often marked with a 160/- . Also objectives designed for metallurgical microscopes are usually designed to work without a cover-slip so they're also marked 160/- and often bear the engraving 'met'. Objective magnifications can range from x3-ish up to x100-ish but anything over x40 usually needs oil immersion, a film of oil (NOT Nuto 32!) between the objective and the specimen. Numerical aperture is a measure of the angle of view of the objective. A high value (i.e. approaching 1) gives good resolution of detail but a small working distance. Objectives with high magnification also have very short working distances. If the objective is an oil-immersion type, its numerical aperture can be greater then 1, say up to 1.3-ish. The overall magnification of the microscope is nominally the objective's value multiplied by the eyepiece's value provided that the tube length is as stated on the objective. Microscopes often have a draw-tube to permit the effective tube-length to be varied a bit but the draw-tube is usually engraved to show when it's at 160 mm. I'll have another look at your instrument photos and then come back with some more comments on the stage movements and illumination. Enough for now, Best regards, Pete W. |
| Pete W.:
--- Quote from: mklotz on October 31, 2012, 07:06:10 PM ---It might be a thread counting microscope, used to determine the "fineness" of a textile. --- End quote --- Hi there, Marv, You could use a vernier microscope for counting textile threads, if you already possessed one. However, if you were shopping from scratch for a suitable instrument for that purpose, the traditional device to use would be one of these: I know this as a 'linen tester' but there are probably other regional names for it. It folds up conveniently to put in the pocket. Best regards, Pete W. |
| Pete W.:
Hi there, all, Here, for interest, are a few photos of travelling or vernier microscopes: First, a Beck instrument very similar to Rob's. Historically, Beck moved from a lacquered brass finish to a black enamel and then on to the grey enamel. On that basis, Rob's instrument is earlier than the one I show. The number Rob quoted is the manufacturing serial number, not the model number. Next, a single axis instrument. I don't know who made this instrument but it was 'badged' by a well-known UK laboratory equipment supplier. The photos show this one standing with its axis of movement vertical but these single axis instruments could usually also be laid horizontally. The microscope can be turned and clamped so that it 'looks' down on the object/specimen or horizontally at it, at right angles to the motion axis. Another variant of the two-axis vernier microscope has one movement axis horizontal and the second vertical but I don't have any pictures of that type. Best regards, Pete W. |
| Pete W.:
Hi there, Rob, A few more comments on your Beck instrument. I agree with Phil that it should have a cross-hair graticule (aka 'reticle') in the eyepiece but you might not be able to see it at first! It will probably be a 'Kellner' eyepiece - that type of eyepiece has a focussing adjustment operated by turning or sliding the very top flange of the eyepiece. This enables the cross-hairs to be brought into sharp focus. Once that's done, you leave it be and you then focus the view of the object/specimen (on the glass plate stage) by means of the knurled hand-wheel on the side of the tube-mount. The classical microscope usually has both a coarse and a fine focus control but vernier microscopes usually have just the coarse adjustment because they don't have very high magnification objectives. A x10 objective and a x10 eyepiece (overall magnification = 100) is plenty for most purposes. The working distance of a x10 objective is plenty big enough for you to be able to top-light your object/specimen. One problem with a single axis instrument is that the object/specimen needs to be supported on the stage with the dimension you're trying to measure accurately parallel to the axis of the carriage movement. With yours, you can measure in two dimensions and get the desired measurement using Pythagoras! :lol: I seem to have made a lot of assumptions about your instrument - it would be good if you could tell us what objective(s) and eyepiece your instrument has. Did it come with a box? They (the boxes) are often very well-made and fitted with places to stow the accessories like alternative objectives. A common problem is that the key to the door of the box gets lost and then someone butchers the lock to gain access! :bang: I tie each of my keys to a trainer lace and tie the other end of the lace to the handle on top of the box! The box is important - dust is a great enemy of microscopes! Best regards, Pete W. |
| mklotz:
--- Quote from: Pete W. on November 01, 2012, 05:37:16 AM --- --- Quote from: mklotz on October 31, 2012, 07:06:10 PM ---It might be a thread counting microscope, used to determine the "fineness" of a textile. --- End quote --- Hi there, Marv, You could use a vernier microscope for counting textile threads, if you already possessed one. However, if you were shopping from scratch for a suitable instrument for that purpose, the traditional device to use would be one of these: I know this as a 'linen tester' but there are probably other regional names for it. It folds up conveniently to put in the pocket. --- End quote --- Pete, I'm not shopping. I already have one of the pocket models you showed as well as a genuine thread counting microscope. The latter is far easier to use for the intended purpose. |
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