New HM spectroscope

[Merlin66 (Ken)]

Jeff,
You're close enough with the focus that you could remove the grating and use the "camera" lens with a 6mm ( or so!) eyepiece to look back through the optical train and move the "collimating" lens ( or the slit - which ever is the easier!) to get the slit 100% in-focus.
Another thing to check is that the slit is parallel to the lines on the grating..
After that it's just practise, practise, practise....
I've tried MANY different methods of getting the star image on the slit and then being able to guide... the one that seems to work the best for me is a "clone" 50/50 beamsplitter. It allows me to find, centre and then guide on a star/ nebula etc etc. Cost about $80...

[theodog (Jeff)]

OK, today I spent time with my Physics class looking at spectra. Gave me an excuse to play with the spectroscope. We set up a neon tube in a light proof cardboard tube, placed a 200mm lens on the spectroscope and obtained the following image.
Data reduction through Vspec.

[Merlin66 (Ken)]

Your off and running!!!!
BTW if you use this gear at school for teaching; can you write-off the costs against tax!!

[sheeny (Al)]

That looks pretty darn good to me Jeff!

Al.

[Merlin66 (Ken)]

Jeff,
With the weather being what it is, I got to thinking!!
If, sometime in the future, you want to "upgrade" the Watkis to use a reflection grating ( 600 to 1200lpm), I think all you'd have to do is remove the transmissin grating and replace the adjustable mirror with a grating.....
If the size of your "camera" lens is OK you should get some excellent results! Two spectroscopes for the price of one (almost!).
What do you think????

[theodog (Jeff)]

Thanks Ken,
I have been thinking the same thing but will use the reflection grating in my next model.
At the moment I'm on the lookout for;
Cheap 2nd hand x by 40mm binoc's
300l/mm refl grating (probably from England P-H) and
adjustable slit (surplus shed seems to be out of stock).

Current model is for experimentation. I have changed the slit holder to include a smaller hole, and am looking at another to hold optical fibres -one for the star, another for a neon reference globe.

[Merlin66 (Ken)]

In my opinion the reflection gratings from Optometrics are the best, and most cost effective.
I picked up a 30mm x 30mm 600lpm for us$125 recently, much cheaper than Edmund Scientific. Never see a P-H reflection grating mentioned on the other forums???
Andre/ Fred at Surplus Shed I'm sure will have the slits back in stock soon; they KNOW we use them all the time!
K-mart usually have pretty cheap binos.....

[theodog (Jeff)]

Originally Posted by Merlin66

Never see a P-H reflection grating mentioned on the other forums???

Ok. I will look at other suppliers.