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Optica b/c Deluxe Spectroscope

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#1 CharlieB

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Posted 17 October 2019 - 05:43 PM

I'm sure this will not have the wide appeal of a rare telescope, but it's a very cool piece of hardware. I have seen other spectroscopes in Classic Scopes, but never this model.  It has three optical trains - one through the Amici prism for the spectrum itself, one for a comparison spectrum and one for a wavelength scale.

 

I found this pretty much by accident on Ebay.  The seller was from the Netherlands and it was advertised as for parts or not working.  I got it for a very good price and even if it didn't work, it was still a nice addition to my Optica b/c collection.

 

When it arrived, I checked to over and the variable slit worked just fine - so far so good.  the little pick off prism for the secondary spectrum source also worked fine (it's a very tiny prism!).  The wavelength scale was visible and I could focus it.  Everything worked as it should.  Then I looked into the eyepiece (actually just a window) to see if I could see any spectrum from a compact fluorescent bulb.  Hmmm.... nothing. 

 

OK, time to take the cover off.  Inside was the Amici prism, but in three parts, all scrambled.  I'm pretty sure these three prisms should be cemented together, but I can't say with certainty.  I taped the three together temporarily, as the all the outer faces are blacked out except for a very small face on each end of the assembly.  I stuck it back together and gave it another try.  Lo and behold!  There was a tiny, thin spectrum with some lines in it! Now I have to find a cylindrical lens for this setup. 

 

Here are a few photos.  The first is the the whole shebang.  Not much doubt it was from Optica b/c, Oakland, California and made in Japan (by whom?).  Serial number 6714.  I wonder what happened to all the others?

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#2 CharlieB

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Posted 17 October 2019 - 05:47 PM

Maybe a clue to the manufacturer, but it's probably just another barrel with a Circle-T.  Tani or Towa?  You can see the opening for the secondary light source (which can close) for the comparison spectrum along with that tiny pick off prism.

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#3 CharlieB

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Posted 17 October 2019 - 05:50 PM

Here's another view that shows the focus and light path adjusters for the wavelength scale.  You can also see the mirror that beams light from a secondary source into the main light path for spectral comparison.

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#4 CharlieB

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Posted 17 October 2019 - 05:56 PM

Here are the internals in the black box.  It's a well made, completely adjustable outfit.  At the top is the optical train for the secondary spectrum.  At the bottom is the Amici prism that's held in place by that strap of metal. 

 

If anyone has used one of these before or even has one, please let me know, as there are a few other questions about this that I'd like to have answered.

 

There is a great video on YouTube on Optica b/c spectroscopes by someone who has owned and used one.  Link (if you are interested).

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#5 Pete W

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Posted 17 October 2019 - 06:22 PM

Very cool!  I have one of the standard b/c Optica spectroscopes, never seen the deluxe, though the instructions I found for mine covers the deluxe version.  Works great on the sun and moon, but haven’t figured out a method to observe stellar spectra.  My rainbow optics grating spectroscope works better on the stars.

 

Thanks for sharing.



#6 CharlieB

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Posted 17 October 2019 - 06:51 PM

I'm pretty sure a modern spectroscope would work better and easier, but these old pieces of equipment are fun to play with and some engineer in Japan went through a lot of trouble to design such a robust item.


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#7 DAVIDG

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Posted 17 October 2019 - 08:47 PM

 I have a couple of different spectroscopes including Optica B/C standard one. Happy to answer any questions on how  to use them.

 

               - Dave 



#8 Don W

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Posted 17 October 2019 - 09:33 PM

Always looked forward to the latest Optica B/C catalog. I knew a professor at the University of Wisconsin-Oshkosh that had a full set of their color and interference filters. Don't think he used them all. He also had a Unitron 3" folded refractor. Very sweet.



#9 terraclarke

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Posted 18 October 2019 - 11:50 AM

 

OK, time to take the cover off.  Inside was the Amici prism, but in three parts, all scrambled.  I'm pretty sure these three prisms should be cemented together, but I can't say with certainty.  I taped the three together temporarily, as the all the outer faces are blacked out except for a very small face on each end of the assembly.  I stuck it back together and gave it another try.  Lo and behold!  There was a tiny, thin spectrum with some lines in it! Now I have to find a cylindrical lens for this setup. 

 

 

 

Yes, they should be cemented.

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#10 terraclarke

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Posted 18 October 2019 - 11:54 AM

The above is from The Solar Astronomy Handbook by Beck, HilBrecht, Reinsch, and Völker, Willman-Bell, 1995; pp. 18.


Edited by terraclarke, 18 October 2019 - 11:55 AM.


#11 DAVIDG

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Posted 18 October 2019 - 11:59 AM

Here are the internals in the black box.  It's a well made, completely adjustable outfit.  At the top is the optical train for the secondary spectrum.  At the bottom is the Amici prism that's held in place by that strap of metal. 

 

If anyone has used one of these before or even has one, please let me know, as there are a few other questions about this that I'd like to have answered.

 

There is a great video on YouTube on Optica b/c spectroscopes by someone who has owned and used one.  Link (if you are interested).

 Your prism assembly is upside down. The larger faces on an angle  should face the eyepiece and slit.

 

              - Dave 


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#12 CharlieB

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Posted 18 October 2019 - 02:38 PM

Thanks Terra and Dave for your comments and suggestions.  I will re-cement the pieces and flip the entire assembly.  I'll report back on the results.


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#13 CharlieB

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Posted 19 October 2019 - 04:17 PM

I re-cemented the prisms, although there must have been a small, exiting fracture on the corner of the large prism, as a small piece of it fell off.  It doesn't seem to be in the light path, so that's good. 

 

After studying the orientation of the assembly, it appears there is only one way the prisms fit into the body, and this is the way I'd shown in the photo.  The only faces that are not blackened, other than the faces that are cemented together, are those small areas that are at 45 deg angles to the incoming and outgoing light paths.  Also, the light coming from the wavelength scale has to reflect off that 45 deg angle, so the orientation is correct.  

 

I am getting a spectrum, so I think everything is working OK.  I directed it close to the setting Sun and saw what appeared to be many absorption lines, but they were quite small without a cylindrical lens to widen them.  I'm going to connect it to a Herschel wedge and ND filters to get a direct view if a solar spectrum the next time the Sun is out.


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#14 Chuck Hards

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Posted 19 October 2019 - 04:22 PM

I know the dispersion was low on these spectroscopes, you had to use very fine-grain film in the old days to record them.  Would a Barlow and increased magnification widen them, Charlie?

 

Nice report, I've never seen one of these close-up though remember them in the catalog.  Still waiting to try my Goto spectroscope.  Lousy weather this weekend.



#15 CharlieB

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Posted 19 October 2019 - 04:32 PM

What is needed is a cylindrical lens.  GOTO spectroscopes came with them and they were embedded in the eyepiece.  I plan to couple to output to a CCD camera, take a few shots, and widen them with photo software.  I just have to fine a good method to couple everything together, which is much easier said tan done.


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#16 DAVIDG

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Posted 20 October 2019 - 10:21 AM

 The width of the spectra is directly related to how well the slit is illuminated. If the  slit is fully illuminated you should see a  fairly wide spectra and you don't need a cylinder lens. When the object is a star, a star is  a point source ie very narrow and that produces a spectra that is also very narrow, hence the need for the cylinder lens to broaden it, so you can see the structure in the spectra. 

  I suggest that you first tune up your spectroscope by looking at a fluorescent bulb. Since the light should fully illuminate the slit the spectra should be pretty wide.  Since the light is coming from the discharge of  different gases in the bulb, you'll see many bright emission lines , especially a bright green one at 546nm from mercury. You adjust the width of the jaws to make the lines their sharpest while keeping them as bright as possible.  You also adjust the eyepiece to have the sharpest lines. The bright green emission line at 546nm is also good to check the calibration of the wavelength scale. 

   With the spectroscope now adjusted, you just need to reflect sunlight onto the slit to see the Fraunhofer lines in the solar spectrum and if the slit is full illuminated the width of the spectra should be wide and you won't need the cylinder lens. It is cloudy here but when I just point my spectroscope at the sky I can see Fraunhofer lines in the spectra.  Here is  a picture of that spectra with my cell phone. It is out of focus so you can't see the Fraunhofer lines but you can see how wide it is so I don't need a cylinder lens. 

 

spectra.jpg

     

 

 

   I still think your prism is upside down or the two end pieces are upside down.  I just looked inside my Optica B/C standard model unit and the long faces of each end  of the prism faces  the slit and the eyepiece. Here is a  picture of the prism at the eyepiece end of my spectroscope. Note that the eyepiece is looking at the large face of the prism.  In your photo the eyepiece is looking at the bottom end of the prism.   I also checked  a couple out by pointing at a light source the spectra is very wide. So I think your narrow spectra is caused by the orientation of the prism. 

 

             - Dave 

opticabc spectroscope.jpg


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#17 terraclarke

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Posted 20 October 2019 - 11:12 AM

Here’s a solar spectrum I took with this little guy a couple of years ago:

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#18 terraclarke

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Posted 20 October 2019 - 11:14 AM

!

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#19 CharlieB

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Posted 24 October 2019 - 10:52 AM

 Thanks Terra & Dave for the spectra photos.  It's pretty clear something is amiss with mine, as I see nothing like your photos.  Again, after playing around with the prism components yet again, I can only find one way to put it together to fit in the case.  I guess I'll have to see if anyone else has one to compare it to.  Also, the x-ray drawing in the manual has a somewhat different prism construction, but the optical path seems similar. 

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#20 terraclarke

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Posted 24 October 2019 - 12:19 PM

I have one just like that Charlie. The top photo shows the front of the device with the optical slit, the bottom photo shows the rear of the device with the eyepiece. The primary spectroscope is the longer tube with the adjustable slit (knurled ring). Light from the object being viewed passes through this tube through the slit in the front and on through the amici prism train. If the slit is closed, the image you see will appear dark. The other, shorter parallel tube contains the comparator reticle scale and a mirror to direct the reticle image downward to the rear amici face. To see the scale, it must be illuminated by light passing through its front opening (no slit here). If light isn’t getting through it, it will appear dark. As long as there is enough light to illuminate the reticle, you will see the scale in Angstroms or nanometers superposed over the spectrum.

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#21 Chuck Hards

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Posted 24 October 2019 - 01:01 PM

Terra, was that one originally for mineralogy?   I've seen a lot of those available online, wondered if they could be adapted to astronomy.



#22 terraclarke

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Posted 24 October 2019 - 01:25 PM

Terra, was that one originally for mineralogy?   I've seen a lot of those available online, wondered if they could be adapted to astronomy.


It is. Both of mine were. It was easy to adapt the one that I showed in my two posts #17 and 18. I just made the copper adapter to bring it up to 0.965 and then used an old 0.965” barlow tube for a housing sleeve. Then I use a 0.965” to 1.25” adapter for that and put it in my 2.5X Powermate which acts as a telecentric to produce a collimated parallel beam.
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#23 terraclarke

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Posted 24 October 2019 - 01:29 PM

I haven’t yet figured out a way to adapt the second spectroscope (with the comparator reticle tho. That one will take some messing with to get the front end into a tube that will fit in a focuser. The reticle could be illuminated with a tiny micro led.

#24 DAVIDG

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Posted 24 October 2019 - 06:36 PM

 Your prism maybe correct and if so the other reason why your getting a very narrow spectra is the slit has been rotate 90 degrees. So the slit is now parallel to the dispersion angle . 

  The test for this would be to  point the spectroscope at a  light source and adjust the slit. The width of the spectrum should not change only the brightness and  sharpness of the structure in the spectra. If the width does change the  slit is not  oriented correctly .

 

 

                - Dave




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