Lhires III to telescope fibre optic cable feed

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  • #574066
    Jack Martin
    Participant

    Has anyone been able to get spectra via a fibre optic cable between the Lhires III and telescope, if so how ?

    Regards,

    Jack

    Essex UK

    #579642
    Andrew Smith
    Participant

    Hi Jack – forgot to say at the telescope end I use a Shelyak fibre injection unit. I think this is the most difficult bit to make with fibre fed spectrographs and well beyond my diy capabilities. 

    Regards Andrew

    #579641
    Andrew Smith
    Participant

    Hi Jack, I have not done this with a Lhires III but I did try it with a LIAS. I used a 1:1 transfer lens(two doublets) to project the exit beam from a 50 micron fibre on to the entrance of the LISA with the slit removed. It worked fine but you get a 50 micron slit. 

    I had an F5.4 telescope which matched the F5 LISA even if the fibre reduced the focal ratio to about F4.5

    This will be the issue with the Lhires III. It is designed for F10 so if you use a 50 micron fibre you will have a large “slit” 

    If you feed it at F10 you will get an F5-6 exit beam and so light loss. You could match the F ratios using transfer lenses but this will increase the size of the “slit” or vice versa. You could retain the slit but then you will get more light loss.

    Hope this helps.

    Regards Andrew 

    #579651
    Jack Martin
    Participant

    Andrew,

    Thanks for your reply.

    Just as I thought.

    LHIRES is not designed to work with fibre optic cables, otherwise others such as yourself would have done it.

    Regards,

    Jack

    Essex UK

    #579775
    Tony Rodda
    Participant

    I have a few fibre bundles, pinhole mirrors, splitters, laser lenses and mounts etc I bought from Ken Harrison a while back.

    “Have 3D printer will print”.  

    If I can find a design (?) I’ll have a go.

    Regards  Tony

    #579777
    Robin Leadbeater
    Participant

    Hi Tony,

    The CAOS group site is a good source for design ideas

    https://spectroscopy.wordpress.com/fibres/

    but the tough bit is sourcing/making a mirror with the end of the (typically 50um) fibre embedded in it. I think most amateur built fibre fed spectrographs have ended up using the Shelyak guide head

    https://www.shelyak.com/produit/pf0008-f-6-50%C2%B5m-injection-unit/?lang=en

    Cheers

    Robin

    #579781
    Andrew Smith
    Participant

    Yes Robin is right. I use a Shelyak guide head and it is a fine bit of kit. They can customise it’s focal ratio and hole size to better suit your telescope within a certain range. 

    Regards Andrew 

    #579786
    Tony Rodda
    Participant

    Half a dozen mounted/unmounted, round and square…

    Any good?

    #579796
    Tony Rodda
    Participant

    Thanks Robin.

    T

    #579797
    Tony Rodda
    Participant

    Thanks Robin.

    T

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