Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.



  • Content Count

  • Joined

  • Last visited

Posts posted by Merlin66

  1. Louise,

    Yes, I designed and built the Spectra-L200.

    I've also designed a FC 120 (folded Classical)  and an MG80 (80mm collimator/ 300 l/mm/ Zuiko 50 mm ) using standard components. Details on the forum.

    I don't have access to 3D printing so I tend to skip these designs....I haven't looked at Christian's Uvex3 design.

    Paul G. and I communicated on his early design concepts.



    • Like 1

  2. Louise,

    Yes, it impacts on the spectral image. I use a hi res, narrow bandwidth, R=10000 Spectra-L200 and have to re-focus between the various target wavelength.

    It's  very seldom that I add sections of the profile together...if you want a full spectrum spread, then a 300 l/mm grating or similar is used and set to the "average" focus.

    I have seen examples where the camera focal plane is tilted across the length of the spectral image, but when compared to the curve above, it's still a compromise.



    • Like 1

  3. If you use the spectrograph on an f7 scope, the beam after the slit will emerge at f7 towards the collimator. This acts as an "aperture stop" - if the beam f ratio is > collimator f ratio then the illuminated part of the collimator will be smaller without adding a mask.

    I use a 30/200 (nominally f7) collimator which works (no masking) well on f8  to f12 scopes. 


  4. I'm pretty sure there's a "freeware" spreadsheet program which reads Excel files...


    For the Spectra-L200 which uses 30 x 30 mm gratings, I used Optometrics (Now Dynasil) https://www.dynasil.com/company/optometrics/

    I made interchangeable holders to allow different gratings to be used - 300/ 600/ 1200/ 1800 l/mm.


  5. Dave,

    I'm pretty sure the PH spectroscope will use a glass prism.

    Fulvio "converted" a PH DV spectroscope to his Spec 600

    http://www.lightfrominfinity.org/Spec 600/Spec 600.htm

    An Amici prism can be used successfully (the late Maurice Gavin's set-up is illustrated in "Astronomical Spectroscopy for Amateurs", p 170) using a barlow lens as a collimator.

    The available processing software (BASS Project etc.) can easily handle the prism non-linear spectral image.


    • Like 2

  6. Interesting.

    I've designed and built a few.....

    What focal length collimator are you thinking about? 

    What resolution?

    A reflective slit plate is a better option than the beamsplitter (I've tried both!)

    A microscope glass slide works well (4/92)

    Checkout our website below for some ideas.

    • Thanks 1

  7. Louise,

    Look carefully at the slit plate.. it is only reflective on one side....

    The numbers look "correct" when viewed from the front (non reflective side)...

    The attached image shows the original OVIO slitplate I designed for the Spectra-L200.



  8. Louise,

    An f6.96 will be a good starting point, no need for reducers/ flatteners.

    Unless you intend to work with very faint, obscure stars/ targets I'm sure you'll find a well centred finder will position the target into the reflective slit aperture.

    I use a 260mm fl eFinder (with a DMK51) on the C11 @f10 (!!!!) and can easily position the target (I use FireCapture with cross-wire overlay) very near the slit gap.

    I use AstroArt or PHD2 for guiding.

    Plate solving with the reflective slit plate has two issues - the limited FOV and the secondary images from the internal reflections in the glass slit plate.

    If I use Plate solving (not very often) then I use the eFinder FOV.



  9. Louise,

    The slit illuminator was used on the early non reflective slits (Surplus Shed) - I used separate beamsplitters mounted in front of the spectrograph to provide a guide image (Using Al's reticle ).

    As I said, the availability of reflective slit plates has improved over the years, and is the recommended solution.

    The QHY5_I will work pretty well as a guider, the imaging camera...start with what you have, you can check the wavelength coverage and probable R value using the SimSpec spreadsheet. I'm still using the ATiK 314L.



  • Create New...

Important Information

By using this site, you agree to our Terms of Use.