[vsnet-chat 601] Re[2]: Low-dispersion CCD spectrograph?

[Stephen J Edberg <"/dd.ccMail=Stephen J Edberg at cas-mosb/"@cc2mhb.jpl.nasa.gov>]

     I have hesitated to jump into the discussion until this point but I 
     think I have something ultimately constructive to add.  The 
     spectroscope mentioned below is intended for visual use, and as such, 
     has sufficient dispersion for an observer to see spectral lines of 
     brighter stars.  I haven't used this particular unit, but I have used 
     others over the years, and I've experimented photographically as well.
     
     The relatively large dispersion of these units may be useable with a 
     CCD imager and a longish exposure.  Photographically they would not 
     work well for stars fainter than about mag. 8.  
     
     I am only now entering the CCD age so I don't have results to report 
     using that medium, but relevant to the discussion is a photographic 
     experiment I performed a few years ago.  (I am presently assigned to 
     work in Florida, far from my records in California, so please bear 
     with the necessary lack of specificity.)
     
     I mounted a small wedge prism in the converging beam between the film 
     (Kodak T-Max 3200) and the optical assembly of an 5" f/10 Celestron, a 
     configuration known as non-objective spectroscopy.  I intentionally 
     aimed at an emission line star in CMa, about mag. 8, and exposed for 5 
     - 10 minutes (no notes handy, sorry).  The negative easily showed the 
     emission line star as a point while normal stars were small streaks, 
     and I had the impression that I would easily be able to detect spectra 
     of something like 3C-273, at mag. 13.
     
     On the basis of this, I think that a wedge prism in front of a CCD 
     would be a powerful combination and able to go much fainter than my 
     photographic experiment.  We just need a manufacturer to make a prism 
     in a filter holder that would substitute for a color filter in the 
     usual CCD imaging set-ups.
     
     Steve Edberg
     
     sedberg@jpl.nasa.gov


______________________________ Reply Separator _________________________________
Subject: Re: Low-dispersion CCD spectrograph?
Author:  mbartels@efn.org at Internet
Date:    09/07/97 10:16 AM


I notice that a new spectroscope is spotlighted in Sky and Telescope's 
new product showcase.  A visual phtoographic CCD model is available for 
US$200, containing a blazed glass diffraction grating and a spectrum 
widening cylindrical lens.  I wonder if this would be 'good enough' for 
brighter targets with medium large amateur scopes.?
     
--
Clear skies, Mel Bartels    Programmer/Analyst, amateur astronomer 
Eugene, Oregon, USA         homepage: http://vsnet.efn.org/~mbartels 
mailto:mbartels@efn.org     atm, atm-digest list-owner
Motorize A Dob: http://zebu.uoregon.edu/~mbartels/altaz/altaz.html

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