High Resolution Spectrograph Project Page 
Uploaded 12/1/13

 
Since
            I am very limited in what I can do with the objective prisms
            and Star Analyzer, a new spectrograph project was initiated.
            The primary use will be for cometary spectra and experiments
            in using it as a solar spectroheliograph. This page I will post
            photos and updates on this project. 


            
  Updates:

              

                

                

                  
October
                  2013 - First try at construction of a f/4 Littrow spectrograph.
                  Images were not of sufficient quality due to trying to project
                  the resulting spectrum too far off axis. A modular design allowed
                  reconfiguration to the next design.
              
            

            

              

                

                

                  
November
                  2013 - Round 2. Construction of a second Littrow spectrograph.
                  This time I reflected the image of the slit rather than the whole
                  wide spectrum. Still, the off axis f/4 light cone was not of
                  sufficient quality to attempt night sky images. Images were highly
                  comatic and exhibited severe spherical aberration. This is because
                  my use of an f/4 achromat to be compatible with the 8" f/4
                  Astrograph was too aggressive. Now I know why most Littrow designs
                  do not try to go any faster than around f/7 to f/10.
              
            

            
What
            was learned.

            
I will have now
            a choice, to go with a slower design such as f/6 - f/8 and still
            deal with some off axis coma, or use the conventional design
            where everything is on axis but requires more complex optics.
            The slit wheel was a mess. Too difficult to rotate without moving
            the scope around, and was difficult to repeatably align. An adjustable
            slit is really the answer, or perhaps some flip in slits which
            are centered every time. I will also have to fully test this
            collimator lens, to see if its of sufficient quality. Finally,
            the focuser mount for the camera was not planar and next time
            a commercially machined unit will be used.



Click to enlarge images to 1290 size

            
 Update
            


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