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Lhires III to telescope fibre optic cable feed

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jack martin's picture
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Lhires III to telescope fibre optic cable feed

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

andrew.j.smith1905's picture
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Fibre fed

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 

andrew.j.smith1905's picture
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Guide head

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

jack martin's picture
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Andrew,

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

Anthony Rodda's picture
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Is there a design for a fibre optic injection unti?

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

Robin Leadbeater's picture
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fibre feed

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/?lan...

Cheers

Robin

Anthony Rodda's picture
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The CAOS website is a gold mine

Thanks Robin.

T

Anthony Rodda's picture
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Last seen: 14 hours 33 min ago
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The CAOS website is a gold mine

Thanks Robin.

T

andrew.j.smith1905's picture
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Guide head

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 

Anthony Rodda's picture
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I have a few variations of these...

Half a dozen mounted/unmounted, round and square...

Any good?