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 Post subject: Lafayette spectroscope
PostPosted: Fri Apr 04, 2008 8:37 pm 
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I seem to have developed a bit of a spectroscope collection and one of the units I own I bought off eBay a while back. It is a bit unusual and is called a Lafayette Direct Vision Precision Spectroscope

Image


Maybe someone is familiar with the original intended use? I think it may have been used to examine carbon monoxide in blood against a standard, much like a Hartridge reversion unit but without the precision wavelength matching.

On the far left the knurled knob can be turned about 10 degrees to reduce the main spectrum to half its vertical height and to introduce a second spectra in the new space. Just visible is a sample chamber where a small cuvette with a lip fits perfectly. The next knurled knob controls the slit width. The black c-shaped clamp I guess is used to hold the standard in front of another aperture. When you shine a light in that aperture (90 degrees to the main orifice) you get the second separate spectra.

The large knurled knob is the focus. Beside it on the left side of the box section is the aperture to source light for the wavelength scale. On the south side of the box section is the focus for the wavelength scale and then there is a lock and an adjustment to move the scale, which can move a significant distance. On the far right is the viewing port.

I am not clear on why the scale would be capable of being moved such a substantial distance - certainly more than is necessary for calibration.

It's a precision unit for comparing two spectra but it would require four hands or a special stand.

Any thoughts?

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PostPosted: Fri Apr 04, 2008 8:52 pm 
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You know what's funny about this hobby? You pick a direction and you can just keep going and going and going.....I had not given instruments a second thought- today took me from geiger counters on ebay (oh, pashaw, of COURSE the old 60's versions that detect small amount of radiation appropriate for such levels as in irradiated stones) to here where someone is tossing around dual precision wavelengths...

No, I have nothing to add. I'm just looking around going holy crap, here's a giant aspect of this hobby I missed for a year and never knew it.


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PostPosted: Sat Apr 05, 2008 11:43 am 
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The label "Lafayette" on this unit is a bit of a misdirection. It is labeled that way because it was imported into the US by the Lafayette Radio Company in the late fifties and early sixties. It was made in Japan by either Atago or Meiji or a subcontractor that those two Japanese firms use. They imported lots of other things too like microscopes and Abbe refractometers and astro telescopes not to mention tons of Japanese made electronics The had a catalog like Allied Radio and before Radio Shack. But they didn't last. There also was a chain called Olsen that had similar stuff.

It is made to essentially be an exact copy of European made hand spectroscopes of the era. The comparison prism was a common featue and can be found on table spectrometers going back to the nineteenth century.

The little test tubes were for solutions and were sized appropriately for the spectroscope (they fit into the hole at the end of the barrel in front of the slit). They were used to look for the spectral shift in hemoglobin that was poisoned with carbon monoxide. The box structure of this spectroscope is unique to it but the rest of it mirrors almost perfectly , similar units from C. Reichert in Vienna (I had one like that with the mirror and the tubes, but sold it to a non gemological collector.) Kruess (They didn't just make gemological stuff) Moller Wedel (Famous cherman optical works) and Beck of England. And others too probably. I wish I had my old Lafayette catalogs (from when I was about eight years old) to see how much they sold that unit for. Probably something like $6.95


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PostPosted: Sat Apr 05, 2008 12:19 pm 
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Gene,

Thanks for the info. I figured you would know.

You were collecting instrument catalogues when you were eight? Has your wife ever asked you to get professional help? :D

Anyway, the hemoglobin shift issue explains the moveable wavelength scale.

It's a very well built item. And set-up properly it could be instructive in the direct simultaneous comparison of two examples of gem spectra.

Thanks again.

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PostPosted: Sat Apr 05, 2008 2:06 pm 
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The black C-shaped thing looks to be a swivel-mount meant to hold a mirror, so that you don't have to position the backlight and spectral source directly in line with the comparison hole.

You can see a little mirror mounted to the side of this comparison spectroscope.


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PostPosted: Sat Apr 05, 2008 2:47 pm 
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The more I think about it, the less likely I think that C-clamp is meant to hold a mirror. Usually a mirror mount would be a complete circle. Nobody would leave an edge of the mirror exposed to chipping like that.


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PostPosted: Sat Apr 05, 2008 4:02 pm 
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Its a mirror mount. The mirror was set in metal just like on a microscope only tiny. If you compare the Kruess one you linked to and Bruces photo you will see they are almost identical except for the box structure on the "Lafayette" In alot of these copies the parts were interchangeable with the original that was copied from. It probably holds true today as well for some of the copies made in India.


Last edited by G4Lab on Thu May 17, 2012 11:39 am, edited 1 time in total.

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 Post subject: Re: Lafayette spectroscope
PostPosted: Sun May 13, 2012 9:28 pm 
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Hi everyone,
I am new to this and for that matter any other forum in general. I recently purchased a Lafayette F-361 Direct Vision Spectroscope without any instruction sheet. I came across a 2008 post for a similar Lafayette F-359 on this forum. Has anybody been able to find any further information on this unit? Any help is greatly appreciated.


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 Post subject: Re: Lafayette spectroscope
PostPosted: Tue May 15, 2012 1:40 pm 
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http://www.gemologyproject.com/wiki/ind ... ectroscope
Start here.

You look into the end opposite the slit. If the slit is adjustable you close it all the way and open it the minimum possible to see the narrowest possible line of light. Look at a compact fluorescent lamp and you will see about six bright lines of color.

If there is a focusing adjustment focus until those lines are sharp. If it has a wavelength scale put some black paper over the illuminator so you won't see it. You can learn to focus that and set it later on after you learn to focus the slit and set it to the narrowest possible. For the beginner the wavelength scale is an uncessary distraction.


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 Post subject: Re: Lafayette spectroscope
PostPosted: Tue May 15, 2012 2:05 pm 
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Hi G4Lab and thank you for your reply. I am familiar in using spectroscopes. I currently own 4 spectroscope, Diffraction grating spectroscope, two Prism spectroscope with scales including a Wollensak- which I have been using for several years and been operating my own Jewelry store for past 14 years. I purchased this Japenese made F-361 without a manual, hence I was looking for the proper usage instruction of this unit. Thank you again.


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 Post subject: Re: Lafayette spectroscope
PostPosted: Wed May 16, 2012 5:13 pm 
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All of the many spectroscopes I have seen, work on exactly the same principles. If you already have four then you should be able to operate this one correctly. Is there somehing particular about this one that is causing you confusion? Post a picture of it. A Lafayette stock number is pretty much meaningless.

By the way your Wollensak, is not really a Wollensak. It is a very cheap Chinese or India made spectroscope with the Wollensak name painted onto it. the Surplus Shed bought all the residua from Wollensak including the right to use the name. When I saw he was painting it on far east crap I sent him an email saying "shame on you" Even though he is within his rights to do so.

Very similar to seeing far east made hearing boosters with the name "Bell and Howell" on them. Nothing whatsoever to do with the origninal company. The Wollensak company of Rochester New York USA NEVER made a spectroscope. One of our list members Dr. Brian the Physics full Professor, bought one of those from SurplusShed prior to them painting the Wollensak label on them and found it wanting. Though it probably is better than no spectroscope and was very inexpensive at least it used to be.

http://www.ebay.com/itm/ws/eBayISAPI.dl ... 65167&rd=1 Here is a contender for the last word in visual spectroscopes. Similar to a Hartridge.


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 Post subject: Re: Lafayette spectroscope
PostPosted: Wed May 16, 2012 9:46 pm 
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It looks identical to the one that was pictured here the F-359. The problem I have with it is that I can not read the side by side comparison. No matter how I ajudst the mirror, 45, 60 dgrees... Unless my expectation are wrong, I should be able to compare two gems side by side. Thank you for the bad news on Wollensak, I already had a cheap Indian made one, did not need a second or third one :( . Given, then this makes Japanese F-361 one of the best one I have. Thank you for the info and the link.


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 Post subject: Re: Lafayette spectroscope
PostPosted: Thu May 17, 2012 11:28 am 
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Its nothing like the the other Lafayette at all. It is a large table model wide dispersion
, research grade spectrometer (albeit a 1920 or so design). It is as large as a table model microscope. The F 359 is essentially identical to your Wollensak and other India made hand spectroscope. The optical layout on those is an Amici prism train, on all three. The physical size and spectral dispersion of your three and the one at the beginning of this thread are all very similar. Hand specs usually disperse the visible spectrum from about seven to eleven degrees. And are by def, hand specs.
The Bausch probably disperses thirty degrees or more.(I may look that up if I remember to) could be fit into a back pack but not any pocket. It is also built like a high precision tool.
The Lafayettes were likely built by Meiji which means excellent quality. And the India ones are probably useable if you are careful. The Bausch is a right angle single prism spectrometer with a large single internal prism and a micrometer controlled turntable that allows you to line up spectral features with an precision adjustable index. This allows wavelengths to be measured ACCURATELY something NO wavelength scale hand spectroscope of the Amici layout can do. However it is not usually necessary for gemologists to make such measurements.


Here is a later model almost certainly made by Meiji more recently. (Recently they have eliminated these from their web pages. They may have been copied in the farther east
, since the advent of the OPL I am less of a student of what is happening in hand specs) Both GIA and the UK GAGTL used to sell one that looked just like this.

http://www.ebay.com/itm/Small-Direct-Vi ... _500wt_948

I recommend people just buy an OPL. You can buy one for about $100 and they have no adjustments and are easy to use and will do 95% of what gemologists need to do very well. Maybe more than 95%.

Quote:
The problem I have with it is that I can not read the side by side comparison. No matter how I ajudst the mirror, 45, 60 dgrees... Unless my expectation are wrong, I should be able to compare two gems side by side.


The external mirror works in conjunction with a comparison prism at the front of the spectroscope before the slit. On most instruments that have them You turn a barrel to flip the prism in and out of the optical path. You know its in the path when the rainbow image has its top or bottom half disappear. Then you can shoot your comparison light into the hole at the side.

As always start out by trying it with a compact fluorescent lamp. I detest them but they are a terrific source of spectral lines. When you have the spectroscope set right you should be able to look straight at a lamp and see its spectrum. Then make its light shine into the side hole and the spectrum will shift position from top to bottom or vice versa.

I would not put it past some far east copiers to put the external mirror on but not have the comparison prism which is an expensive component in comparison to the selling price of these things. But your Lafayette should have one and it should work.


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