GOTO Kogaku Star Spectroscope
Posted 07 January 2010 - 01:18 PM
I just scored a set of star spectroscopes in their original boxes. Both labelled GOTO Japan on the barrel, but one in a Lafayette box and one in a GOTO box.
Here are my questions: I'm at work with no scope to put them into. When I look through the spectroscopes at a bright light I see a spectrum, but only at the very edge of the field. Is this expected?? Also, the tilted optical element closest to the telescope seems loose with no obvious way to tighten it. Any suggestions?? Is the tilted element just a reflection grating??
I'll post a picture of the pair later.
Posted 07 January 2010 - 02:26 PM
I have what I think is the same spectroscope. The one I have is a narrow tube (about 1/2" dia) inside of which is an assembly of 3 prisms cemented together. The #2 and #3 prisms increase the angular dispersion of it's predecessor. The tube attaches to the top of an eyepiece on one end and the eye end has 3 interchangeable cylindrical eye lenses of different powers. The cylindrical lenses disperse the spectrum in the direction perpendicular to the direction that the prisms do. In this way the thin spectrum of a star is spread out to a finite, observable width perpendicular to the spectrum. Which lens you use depends on the brightness of the star under observation. You want to spread out the spectrum but too much spread makes it too dim to observe.
The prisms in mine are held in the tube with some type of cement which has dried and shrunk. As a result the prisms are loose in the tube but they do not come out. I suspect a small drop of a cyanoacrylate glue is all that would be needed to secure the prisms.
Posted 07 January 2010 - 02:43 PM
Posted 07 January 2010 - 04:00 PM
Paul: Sounds right. It looks like that one loose prism could be reglued, and on close inspection I see the glue remnants. I have all three dotted eyelenses for each unit.
Funny: I've long wanted one of this type of spectroscope but never bought one. Today two fall into my hands without me even looking. That may be the key!!
I need to go through the rest of the boxes of stuff I picked up to see what else is inside! Probably no 9" apo's though :>(
Posted 07 January 2010 - 04:36 PM
Posted 07 January 2010 - 04:42 PM
Posted 07 January 2010 - 04:44 PM
Posted 07 January 2010 - 05:59 PM
Posted 07 January 2010 - 09:15 PM
This thread from a while ago should help...
Goto Spectroscope with Instructions
I believe Hiroki(Galakuma) might have a full instruction manual. Unfortunately, I have tried to find it amongst my documents and can not and also checked his site and could not find it.
I have been looking for one of these for about 4 years with no success. Congrats on finding 2!
Posted 07 January 2010 - 09:45 PM
Today two fall into my hands without me even looking.
Wow, literally nice catch(es)! You do know these will only work in Goto Kogaku scopes, right? And not in that big awkward ugly oafish 6" scope of Steve's, but will rather well in my 3"
Posted 07 January 2010 - 09:48 PM
Posted 07 January 2010 - 10:09 PM
I have a 3" too , and a 4", and a 1.6", got 'em covered.
Sheesh! Well, I also have a 2.4", I just didn't want to brag (too much)
Friends with a guy who has a 6" and 4" and 3" and even 1.6" Goto Kogaku telescopes WOW
Posted 08 January 2010 - 06:35 AM
Perhaps two spectroscopes! The Lafeyette version is in a slightly smaller box and fits into smaller eyepiece tube.
I'm also the owner of a Goto Spectroscope. Got mine from Edmund Scientific many, many years (early 70's) ago. An excellent instrument for visual use.
Posted 08 January 2010 - 08:18 AM
I opened mine, to see that a prism has come loose since I last used it (there's a trend here), to see if the instruction sheet was there. Mine is signed Goto Kogaku in the tube, another variant. The sheet is tiny, just a diagram, but here it is anyway:
Posted 08 January 2010 - 08:30 AM
Interesting drawing. I had no idea that another eyepiece and adapter were required! Neither came with the setups I received, I think. Now I need to search a little more diligently through that tub of material.
BTW: wrt our conversation yesterday, I found a boxed ~ 4" diam. transmission grating and some optical components that might be part of a spectrohelioscope. More on that once I figure it out...
Posted 08 January 2010 - 10:07 AM
I have couple of these also. There is no slit in them, so to use them as a hand held device, what works well is to view the reflection off of chrome cylinder like an eyepiece barrel. The reflection along the length of the tube is very narrow and acts like a slit. This maybe why your not seeing the spectra in the middle of FOV. Using this reflective slit technique, I can easily see a number of the major dark lines in the Sun spectrum, and many bright emmission lines in a fluorescent lights.
When you use the spectroscope with a telescope, a star acts likes it's own slit, since it is a point source.
Posted 08 January 2010 - 08:29 PM
In my unit, the prism train is embedded in a 'pitch'-like material, which appears to have been simply trimmed down to size with a knife. This assembly then fits snugly into the metal tube, although there is (and always was) a little looseness.
I'd certainly not say that the three culindrical 'eyepiece' lenses are made for specific magnitude stars. It depends on the scope's aperture, and just how bright the star appears in its eyepiece.
I did find that with a 4.25" aperture I was limited to seeing spectra in stars brighter than 2nd or 3rd magnitude.
Posted 03 August 2010 - 03:28 PM
Posted 04 August 2010 - 05:17 AM
The Goto star spectroscope is threaded to screw onto a Goto eyepiece. The top of the eyepiece unscrewed and the star spectroscope screwed on. Edmund sold an adapter that let you slip the star spectroscope over a generic eyepiece. You would focus a star in the eyepiece and then slide on the spectroscope. The three cylinder lenses widened the spectrum to make the lines more visible. You shouldn't just screw on the cylindrical lenses. You need to turn the lenses so the axis of the cylinder is aligned with the spectrum. I think the spectrum is a little brighter than the grating spectroscope sold by Rainbow Optics, but the grating spectroscope is currently available and much less costly than the dove prism spectroscope.
Welcome to the Classic Scope Forum. I have both spectroscopes but admit I find the Rainbow Optics Spectroscope easier to use. Both are quite excellent.
Posted 11 August 2010 - 10:50 AM
Posted 11 August 2010 - 01:21 PM
I did exactly what you asked using a unit I purchased from Surplus Shed. I turned an adapter to hold to the unit in the focuser and all you need to do is open the slit not remove it. You'll need a cylinder lens that you place over the eyepiece to spread the out the width of spectrum so you can see the absorption lines.
I have a normal slit-based spectroscope. Can this be adapted for astronomical use by removing the slit end and seated into a sleeve that will fit into the focuser? What about eyepieces- it has just the one built in. Thanks.
Posted 19 August 2010 - 09:16 PM
Posted 19 August 2010 - 09:55 PM
My slit wasn't very good either. I removed the jaws and carefully polished the edge of each blade against 1200 wet dry sand paper placed on a flat piece of glass. That removed all the nicks in the edge. I then reinstalled the jaw blades and aligned them so they close down evenly. It now works very well when I want to use it to observes emmission lines in lights sources like CFL bulbs or neon signs or absorption lines in the solar spectrum by looking at a reflection of sunlight.