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I read a phd thesis on the opitcal design of Kiwistar (nz optical company) Optics kiwispec echelle spectroscope

https://ir.canterbury.ac.nz/bitstream/h ... sAllowed=y

Maybe others have seen this before, but I found the description of the optical design and choices quite interesting and educational, particularly the choices of white pupil (a second collimator after double pass of the light from entrance, off the primary collimator to echelle, back to primary then to secondary collimator).

Using a shorter focal length secondary collimator reduces the required size of the final camera optic (i.e. can be a higher f number). After lots of time playing with simspec I've come to realise how important this can be in order to avoid the need for a very (expensive and difficult to achieve) low f number camera optic.

Also the cross dispersion is by a grism, allowing simpler changing of the cross disperser as the optics remain on axis.

Not amatuer, but it might be useful in future design of amatuer echelle spectrographs.

Hi Hamish,

I can't connect in that address is posible it has a little mistake ?

Regards, Joan.

https://drive.google.com/file/d/1adokAZ ... sp=sharing

It appears that the university computer system is on maintenance, so I have uploaded it to google drive.

Many thanks Hamish,

Congratulations New Zealand for this spectrograph.

The Kiwispec would be the dream of the most of us. But the reality is another thing.

Regards, Joan.

Indeed it would be a dream. But some interesting lessons. I like the chapter about the choice of cross disperser. By using a grism rather than prism or grating alone, the curvature of the orders is reduced.

And the asymmetric focal lengths of the primary/secondary collimators reduces the need for a fast lens being required for the camera.

meanwhile I struggle along building my wooden classical design (with reflective mirror slit guider! ). A wise man said "do not build your own spectrograph". But the allure is too strong.

Hi Hamish,

I understand all what you say, but in Catalan language we have the expresion "tocar de peus a terra", "touching with the feet to ground" in other words, we're playing the cards we have.

I think you have very well that don't follow the advice from your wise man.And if your wise man has been in mistake ? Everyone may have a bad day..

Here near Mediterranean Sea, for some thousand years ago we're having a lot of wise men, can you think how many a lot of bad days we had ago?

I wish you a good success in your build spectrograph I believe that you have following this exciting way and I hope nearly we may see the first results. Go ahead !

Very friendly, Joan.