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 Post subject: Spectroscope - Not sure where I'm going wrong
PostPosted: Mon Sep 28, 2020 7:58 am 
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Hi everyone,
I'm hoping someone could pick-up where I'm going wrong with my spectroscope as I'm having trouble getting the hang of it.
I've owned a really cheap mini item from eBay for the last few years but never managed to get any useful results with it, so when I saw a Kruess model for sale secondhand I snapped it up.
I've had it for a couple of days now and I've read some guides online, bought the OPL book (only read a little of it so far), and experimented with a few different ways myself. No matter what I do with varying gemstones, I can only see an uninterrupted spectrum: no absorption lines or bands.
I started out with an LED torch but after reading some guides I've switched to an incandescent mini maglite. I've tried placing the gem face down and face up, on a black polishing cloth, with lighting from the side. I've also made myself a "holder" out of Blu-tack to attach the gemstones to the end of the Mag-lite, allowing transmitted light only to pass through the gem not around it. All other lights in the room are off and the blind is closed. Gemstone wise I've tried Zircon, Peridot, Emerald and Sapphire.
The only way in which I have managed to view an absorption line is by looking at my computer monitor which gives me a thin line between the yellow and green bands.
The scope has adjustments for focus (the tube changes length) and for brightness (turning a knurled ring near the end of the tube). I haven't messed around with the focus or calibration for the wavelength scale yet as that seemed pointless until I can consistently view some varying spectra.
Very many thanks in advance if anyone can offer me some advice please.
Dan


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 Post subject: Re: Spectroscope - Not sure where I'm going wrong
PostPosted: Mon Sep 28, 2020 5:14 pm 
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Krüss makes a reliable product.
Can you post a picture of the Kruss you own?
Look at an overhead fluorescent light fixture. You should see several lines.

Does it have a fixed slit with an adjustable focus? Or are both fixed or adjustible?

I always suggest starting out with a synthetic,flame fusion ruby.
Try both transmitted and reflected light.
You can use a maglight for your light source but a fiber optic is the best.

The spectrum for ruby is diagnostic:


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 Post subject: Re: Spectroscope - Not sure where I'm going wrong
PostPosted: Mon Sep 28, 2020 6:35 pm 
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The easiest stone I have found to first see a good set of bands and learn on is with pyrope-almandine, and spessartine garnets. Then try to find the "Zircon Line" in a Zircon.

Once you get the hang of seeing these, you can expand your stone samples. I suggest you use the GIA Lab manual as a guide and look at the stones where the manual list the spectrum as a significant ID feature.

The environment (lighting) , positioning, and lighting of the sample are most important. I use a fiber optic halogen light source. I wish I could give you a simple recipe for the setup but it seem to require tweaking for every sample tested.

Truthfully these days in my lab, I use Digital and RAMAN spectroscopy much more than optical these days.


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 Post subject: Re: Spectroscope - Not sure where I'm going wrong
PostPosted: Mon Sep 28, 2020 8:33 pm 
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Maladriak, you may want to check out this aticle by Richard Hughes
https://lotusgemology.com/index.php/lib ... s-gemology.

Again, please post a picture of your spectroscope. I have several and can help you out once I see what we are up against. :D


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 Post subject: Re: Spectroscope - Not sure where I'm going wrong
PostPosted: Tue Sep 29, 2020 6:25 am 
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Thank you for the responses.

I've attached 3 photos which show the adjustment screws.
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File comment: Kruess Spectroscope 1
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File comment: Kruess Spectroscope 2
Kruess Spectroscope 2.jpg
Kruess Spectroscope 2.jpg [ 77.37 KiB | Viewed 661 times ]
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File comment: Kruess Spectroscope 3
Kruess Spectroscope 3.jpg
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I'm afraid I don't know if the slit is adjustable, I don't know what that would look like.

Focus of the spectrum, when you look through the scope, can be changed by loosening the screw and sliding the long tube in or out.

I don't have a fluorescent tube in the house unfortunately but I viewed one of the energy saving "coiled tube" type bulbs and hope that's ok. You were quite right, I saw an extremely busy spectrum with either a line or a bar separating every one of the colours from it's neighbour. Previously I'd checked with the strip light above my desk, but now I think back, it was possibly an LED daylight temperature one.

Unfortunately I don't own a flame fusion Ruby, not that I could be certain of. I've tried both reflected and transmitted light using Zircon and Peridot among a few others though, but no luck seeing any lines or bars at all.

The Maglight I am using is a Solitaire (it was the only one I could find that was incandescent not LED) and due to its size is not very powerful. Could this just be a lack of light problem? By a fibre optic light, do you mean the ones with a goose-neck coming out of a largish box? If it's the ones I'm thinking of, they would be out of my price range I think. Would a realistic price be £300 or £400 for one of those lights? I only paid £100 for the Spectroscope itself.

I'll try the pyrope-almandine, as I have plenty of those in differing sizes and the same for some spessartines as suggested by 1bwana1. Unfortunately I don't have access to a GIA lab manual but I'm going to read the Lotus link Barbra has posted and will also continue working through the OPL book by Colin Winter.

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 Post subject: Re: Spectroscope - Not sure where I'm going wrong
PostPosted: Tue Sep 29, 2020 8:19 am 
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The tip about using a pyrope-almandine garnet worked really well, thank you. I managed to see a spectrum similar to that shown in GT Pro.

Using a stand for the Maglite, rather than my wobbly hands, seemed to help as well. I can highly recommend having a "sticking and gluing moment" rather than buying the more expensive proper ones.

Attachment:
File comment: Cardboard holder for Maglite Solitaire
Maglite holder for Spectroscope.jpg
Maglite holder for Spectroscope.jpg [ 93.72 KiB | Viewed 656 times ]


I maybe worried too soon that something was wrong. I just needed a little guidance and a whole lot of practice. Lots of reading and practicing to be done next I think, starting with the article by Richard Hughes.

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 Post subject: Re: Spectroscope - Not sure where I'm going wrong
PostPosted: Tue Sep 29, 2020 11:37 am 
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That pic helped a lot.
It is Kreuss 1504. I think I may have one of these somewhere.

This pdf contains the instruction manual for the 1504. Scroll down


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 Post subject: Re: Spectroscope - Not sure where I'm going wrong
PostPosted: Tue Sep 29, 2020 3:17 pm 
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hi maladriak

I have this spectroscope. It does indeed have an adjustable slit. In fact, it has adjustable everything that can be adjusted, including the wavelength scale that you see through light in the smaller tube.

So it works really well when you know how to tune it. But without knowing what you are looking for, it can be difficult to know how to adjust everything for best result.

Also, a little maglite should work fine. Just make sure that no light at all is leaking around the sides of the gem. I usually do this by poking a pinhole (smaller than the gem) through a piece of cardboard that completely covers the flashlight window, and then set the gem to cover the pinhole.


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 Post subject: Re: Spectroscope - Not sure where I'm going wrong
PostPosted: Wed Sep 30, 2020 3:13 am 
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Hi Brian,

Thank you for the advice, I'll try the method you suggest and see how I get on. It's reassuring to know that the light source is strong enough.

Barbra,

Thanks for the PDF of the instruction manual, I didn't get one of those with mine. And thank you to the magic signature fairies on the other thread :D

Dan

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 Post subject: Re: Spectroscope - Not sure where I'm going wrong
PostPosted: Wed Sep 30, 2020 1:03 pm 
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maladriak wrote:

And thank you to the magic signature fairies on the other thread :D

Dan


Our fairies are always on standby. :D
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