24 l/mm is too coarse for normal use though it might make a useable cross disperser in an Echelle spectrograph.
I was also wondering what difference the scope makes to your spectrograph design. I guess the faster focal length scopes will require quicker lenses as collimators which means more expensive camera lenses
???I have been pondering over the 10" Shcmidt newtonians for a while now and will probably purchase one when we move into the new house this summer. Would this scope be appropriate to spectroscopy.
Yes the speed of the spectrograph optics needs to match the telescope. You can always use a Barlow or reducer to do this though. The main thing is to make sure you have enough focus travel to allow the slit to be placed at the focal plane. The size of the spectrograph tends to be dictated by the aperture. The bigger the scope the bigger bigger the spectrograph. big scopes means big star image/slit size and therefore greater dispersion for the same resolution . You can make the image smaller by going faster but then the components need to be larger. A 10 inch is a good size (It is the design aperture for the LHIRES III for example)
Would it be possible to have a fixed collimator after the slit which directed the beam at the grating and then using a second zoom lens you could view different regions of the spectrum reflected from the grating in various resolution by zooming the second camera lens in and out?? The advantages here would be that you would be able to get many varying resolutions specific to the type of study you required??
This is similar to the approach Maurice Gavin uses with his WPO spectrograph (interchangeable lenses)
http://www.astroman.fsnet.co.uk/newspec.htm You need to be careful though. Just changing the imaging lens changes the dispersion but does not necessarily change the resolution. (you magnify the spectrum but you also magnify the apparent slit size so you can end up back at square one.) Generally collimator and imaging lenses
end up similar for best performance
If you fancy designing your own then Christian Buil's site is a mine of information including excel spreadsheets to test out the performance
Cheers
Robin
EDIT: I have just realised Maurice Gavin's design is a littrow so the collimator and imaging lens are one and the same so they are always matched -which makes my point ;-)
