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Thread: Spectroscopes

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    Default Spectroscopes



    Does anyone here have any experience with the Lhires spectrographs? About 15 years ago I purchased a Rainbow Optics spectroscope which consisted of a precision diffraction grating which screwed into 1 1/4 inch eyepieces, plus a lens that widened the spectral image. It cost about $200 and is still sold (see Sky and Telescope ads. I really enjoyed using the little spectrograph. Looking through the eyepiece I could see a bright, thin (about 3 mm thick at the widest point) long spectrum of a star with several fainter secondary spectra. The spectrum could appear to be several mm thick and several inches long. Dark lines were apparent at various locations in the spectrum depending on the stellar classification. Cool M stars showed many dark lines. This was a great way to learn about spectroscopy which is how we know the temperatues, composition and motions of stars and galaxies.
    As an upgrade I was wondering how well the much more expensive Lhires spectroscopes work. I would appreciate comments by anyone who owns one or has viewed with one at a star party or with a friend's scope. How do they work as a purely visual tool? Is it easy to use them to photograph spectra? How long would typical exposures be? Can they be easily used to get solar spectra?
    Thanks. JimS

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    Default Re: Spectroscopes

    The LHires is a big step up from the RO spectroscope. By science standards it is in reality a low-resolution spectrograph at approximately R=18,000 - true high-resolution astronomical spectrographs are in the range of R=60,000 and higher.

    We have one here that has been used on and off for public outreach for solar, planetary, stellar and atmospheric spectroscopy programs. The unit is moderately expensive, about $4700 (really more all in, the gratings range from about $380 - $600), by the time you have everything in hand about $6000 for a complete unit, less telescope, mount, and an imager. It is optimized for an f/10 SCT in the 8" - 14" range. It is heavy, and needs a substantial mount to handle and balance it, along with front-end OTA counterweighting.

    With the admission that I am biased based on exposure to true high-resolution equipment, it is a nice, but expensive component. If you have a true interest in the science, it is probably a worthwhile investment - otherwise it is an expensive boat-anchor.

    As a pure visual instrument, you're much better off with the less expensive and easier to use RO unit. If you want to record, image, and analyze spectra, and understand how to use a tool like IRAF/ICE, it is useful.
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    Default Re: Spectroscopes

    AustinPSD: Thanks. Sounds like it might be an expensive disappointment. I assume that the great spectrographs I have seen in astronomy books are made with the high end equipment. I am guessing from what you say that it is less of a jump from the RO to a LHires than from a LHires to the high resolution photos seen in books. The RO is a great little instrument and at least gives a basic idea regarding what spectroscopy can do. Since I don't have a boat, maybe I'll just save the $6000. JRS

 

 

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