Forum der Vereinigung der Sternfreunde

Hi,

I'm pleased to announce our new CAOS blog at:

http://spectroscopy.wordpress.com

The blog is still in its beginning, but
in particular you may find interesting the articles writen
by our colleage Dr. Gerardo Avila about fibres at:

http://spectroscopy.wordpress.com/category/fibres/

I hope you can find them useful.

Best greetings
Carlos Guirao

Hi again,

We´d like to share with you the development of our unexpensive
image slicer with mirrors. The complete story is availabe at:

http://spectroscopy.wordpress.com/category/fibres/

We plan to extend the article in the coming days with more pictures,
manufacturing details and mechanical drawings.

I hope you may enjoy it.

Cheers
Carlos Guirao
CAOS

Hello Carlos,

that's very interesting !!!


But on the other hand: What about the Baches echelle spectrograph? That wunderful instrument, when can we take it in our hands?

Cheers
Lothar

_________________
Herzliche Grüße / best regards

Lothar

https://lotharschanne.wordpress.com/

Hallo Freunde,

ich kann nur empfehlen, euch die LWL-Artikel/Hinweise auf der neuen website der CAOS group anzuschauen. Ist noch wenig da, aber das ist wirklich interessant.

Und wenn das alles erscheint, was da angekündigt ist, .... das wäre toll.

Beste Grüße
Lo

_________________
Herzliche Grüße / best regards

Lothar

https://lotharschanne.wordpress.com/

Hi Carlos,

really interesting. In summer 2006 we also had a long discussion about image slicers,

http://spektroskopie.fg-vds.de/forum/viewtopic.php?t=36

and Micheal Koch came up with a prototype that was related to yours:

http://www.astrotreff.de/topic.asp?ARCH ... C_ID=45925

Of course I appreciate a cooperation between our groups, although our current problem with fibers is not so much resolution as S/N and coupling the fiber to the telescope.

Are you willing to reveal some details about the new spectrograph?

Regards,
Udo

Hi Udo

Gerardo just showed to me the next article for our blog:

Linking a telescope to a spectrograph through a fibre

He's really working hard to have it ready asap. I've seen the draft
and I can promise you it is quite extensive, so I hope it could answer most
of your questions.

Regarding our next instrument: it is a fibre
linked spectrograph, for which we do not have a name yet.
We are aimed to make it fully available in our blog in the coming weeks, starting of course with specifications. I can advance
you that most of our efforts are aimed to minimize the fibre looses by matching F#s at both ends of the fibre.

Cheers
Carlos

Hi Carlos,

great news. I hope your solution will be simple enough, that we amateurs ( without a sophisticated machine shop in the background) can benefit from your ideas.

I think that we know how to do it in principle. But tiny details can make it a mess. E.g. the attached image shows jupiter close to the pinhole in front of my fiber. The edge of the hole gives multiple reflections causing the auto-guider to drive crazy...

The echelle fraction here will also welcome your new spectrograph. I am really curious ...

Greetings,
Udo

Hi Udo,

We have not use any guiding system (yet), just good tracking and a little bit of video-console experience with the telescope control buttons.

We do not see however such reflects from the edges of the pinhole as yours, but this does not mean anything. I can imagine that we may face the same problem if we had a guiding system.

Let me mention that we normally use very thin Ni plates of from 13u to 16u, inclined at 15 deg (in our next head-design for fibers the plate will be inclined 10 deg only).

Cheers
Carlos

Hi

We have post a new article in our blog with the title:

"Slit/Pinhole Flux Calculator"

and available at:

http://spectroscopy.wordpress.com/category/fibres/

We hope it could be useful

Cheers
Carlos Guirao

Hello Carlos,

that's fine that you post your news in our forum. Thank You.

Lothar

_________________
Herzliche Grüße / best regards

Lothar

https://lotharschanne.wordpress.com/

Hi,

The presentation of BACHES at the ATT 25th Essen (Germany) is
available in PDF format at:


http://spectroscopy.wordpress.com/documents/

Cheers
Carlos Guirao

Hi Carlos, when Klaus Vollmann an me have been at ESO we already disussed BACHES with Gerardo. Now it seems to be ready, indeed. What does "high mechanical stability" means? What is your mechanical, and hence, spectroscopic, drift? Considering other Echelles (e.g. HEROS, FEROS, Shelyak, etc) who all work with fibers for maximum spectral stability, this is an important issue.

Second, how do you feed calibration light?

And third, Baches is optimized for a focal length of about 3m (right?). Now, how did you tune it for the 1m telescope? I believe you need a focal reducer.

Cheers, Thomas

Hi Thomas,

Special care was taken to design mechanically the spectrograph body to
get it as stable as possible. In the engineering prototype the
maximum spectrum shift was less than 9 microns along the dispersion.
Complete description of tests will be provided via Baader's web page.

A Th-Ar Calibration lamp will be mounted on the body of the
spectrograph. The injection will be with an optical lens opened to F/10
and available with a motorized mirror

Yes, BACHES is optimized for telescopes up 40 cm and F/10. The 1m La
Silla telescope was opened to F/13 and we used a celestron 0.63 reducer,
so the input beam was F/8.2 Of course it was still not well matched and
therefore there was a big vignetting. F/10 to F/8.2 gives 33% losses and
the image of the star was much bigger than the 25 um slit. The seeing was between 1 and 2 arcsecs thus the efficiency passing through the slit
was between 54% and 27% and reduced further to 36% and
18% at the collimator of the instrument (F/8.2 vs F/10)
(we used our slit calculator to estimate the passing flux:)
http://spectroscopy.wordpress.com/2009/ ... /#more-525

Cheers
Carlos Guirao

Hi Carlos!
Ok, very important information, although 9 microns would be too much. Somebody told me that you now use a 10mm base plate instead of the thin prototype plate. But what about the weight then?
Does that infect the possible bending? I mean, this is additional mass...
Hm, when applying a 0.63 Baader-Shapley the outcoming focal length depends on the lens position. If the 0.63-factor applies, the 1m f/13 would result in f=8.2m (f/8.2 as you said). Then a 2" seeing disk results in 80 microns in the focal plane. You use a 50 micron fiber. Is that the reason for your "efficiency passing through the slit between 54% and 27%"? If yes, this is only because of vignetting at the fiber pupil, FRD, etc. excluded. Korrekt?

Cheers, Thomas

Hi Thomas,
9 microns were measured between extreme positions.
What it should counts is the flexure between positions before and after a long exposure.
1400 grams as picture in slide 4 in
http://www.eso.org/projects/caos/presen ... ion_v5.pdf
The Th-Ar lamp and its housing is not that heavy,
The flexures reported were measured with the calibration unit in.
No fiber was used, just the 25x125microns slit. At F/8.2, a 1" seeing permits 54% efficiency through the slit, 27% with a 2" seeing. Try yourself the flux calculator at:
http://www.eso.org/projects/caos/fibre/ ... lator.html

Regards
Carlos

Hi Carlos,
What type of lamp is it when you can mount it inside the spectrograph? I guess this is not a common hollow cathode lamp? The housing of my direct coupled echelle spektrograph is a good deal bigger but there is even no place to mount one of these 50 mm bulbs!? Sorry I'm just a bit confused.

Another question. The optical system of your spectrograph operates with two slits, how can you arrange to change the slits and fit it in the right position.

Best wishes

Tobias

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Dein Projekt. Mach es fertig, bevor es Dich fertig macht!

Hi Tobias,

See slide 11 of
http://www.eso.org/projects/caos/presen ... ion_v5.pdf
shows the instrument at the telescope with the calibration unit, a Th-Ar
lamp from Juniper Ref. 4160AHP , I think 1.25".

The slits are fixed, a mask below slides between them.

Cheers
Carlos

Hi,

A new article about tapered fibres is available at
our blog:

http://spectroscopy.wordpress.com/categ ... al-fibres/

Cheers
Carlos Guirao