Anyone tried Zeiss reflective gratings?

[Bernard Heathcote]

What I have found surprising and very interesting in Uwe Zurmuhl's "Spectroscopy with Medium-sized Objective Gratings" article in the latest BAV Magazine Spectroscopy is Fig.3 (below) comparing the Zeiss versus Thorlabs transmission gratings.

The very obvious superior Zeiss performance makes me wonder how much our slit spectrographs, that mostly use Optometrics/Thorlabs reflective gratings, would benefit with Zeiss gratings (not cheap), assuming the superior performance also applies to their reflective gratings.

Can anyone confirm this Zeiss improvement with slit spectrographs?

Cheers,
Bernard

[Stu Todd]

Compliments of the season Bernard.

Whilst not Zeiss, Joan Guarro Flo found great improvement in using a Richardson grating over the Thorlabs equivalent in his T_NOU echelle, so I imagine a Zeiss grating to be superior still, with the price tag to match no doubt! Perhaps Thorlabs shouldn't be the "go to" manufacturer after all.

Joan's improvements are described in the thread below this one.

Stu

[Joan Guarro Flo]

Hi Stu,

It seems that we're a bit confused, Uwe Zurmühl, -- you can see here from page 25, https://bav-astro.eu/images/Issue_12_21.pdf --,
talks about a comparison transmission gratings, and has used them in different design that we use. That last isn't important because
with efficiency and a lot of evidence, Uwe shows us that Zeiss gratings are well done and Thorlabs ones are defectuous.

Really exist three grating manufacturers of the first line, Richardson, Toshiba and Zeiss. There's another old manufacturer, Optometrics,
but that company changed ownership many years ago, although I bought them an echelle grating 63.43º 79 l/mm. 9 month ago, when I read
and realized this report in the VdS, https://forum.vdsastro.de/viewtopic.php?f=2&t=4371. I tested the Optometrics one and it has double the efficiency than the Thorlabs, it's the same that made the x2 de surface of my telescope !!. I put it in a NOU_T that I sent to an observer.

I bought a second echelle grating from Optometrics, it was of another manufacturing series and unfortunately, in the test I got the same result
as the Thorlabs one.

Currently, the closest company to us is Richarson ( by ED ), I have been using their echelle gratings in my NOU_T echelles with similar results as the first Optometrics one.

You can see in this picture the same points there are in different places, it passed when I'd changed the echelle grating. With the Richardson
one I've noted a remarkable resolution improvement and reduced the integrations half time. The Thorlabs one, spreads and loses a lot of light
out and erases fine details in the final graphic, but it's very good at making tungstene images, ( just ).

Have a Good New Year ! Cheers, Joan.

[Hamish Barker]

Hi Bernard,

Did you receive any quotations for Zeiss reflection gratings? I'm always keen to chase the best value improvements of magnitude/$ . If S/N can be boosted significantly by moderate investment, that sounds very attractive.

Cheers,
hamish

[Bernard Heathcote]

Hi Hamish,

I did contact Uwe, asking for more info on the Zeiss grating, and below is his helpful reply ... you might choke on the price!.

Cheers,
Bernard

It is indeed difficult to get information about the ZEISS gratings. Perhaps one reason is that they mainly sell reflection gratings and the transmission versions are only a small niche market.
On page 5 and 6 in the attached catalog you can find the reflective counterparts of the gratings I used. However, the transmission gratings have different product numbers:
263232-7015-623:   300 l/mm, (mechanically) ruled area about 65 mm x 60 mm (my version was slightly larger), blaze wavelength 712,5 nm ( = 2850 nm/4)
263232-7014-323:   600 l/mm, (mechanically) ruled area about 70 mm x 50 mm, blaze wavelength 575 nm ( = 2300 nm/4)

The price of those gratings was 585 € (without tax).

My sales contact person for quotation was Mr. Moeller:

Tobias Moeller
Geschäftsfeld Components
Key Account Manager
Carl Zeiss Spectroscopy GmbH
Carl-Zeiss-Promenade 10
07745 Jena, Deutschland

Telefon: +49 3641 64 1717
Mobil: +49 151 151 96883
Telefax: +49 3641 64 2485
E-Mail: tobias.moeller@zeiss.com
http://www.zeiss.com/spectroscopy

To my information, Mr. Moeller will leave his position in the near future (but any E-Mail to him will be probably forwarded).
As an alternative, you could contact Gabriele Höfer (gabriele.hoefer@zeiss.com).

 

[Bernard Heathcote]

Hi Hamish,

You can get the Zeiss gratings catalogue and info at:
https://www.zeiss.com/spectroscopy/prod ... #downloads

Cheers,
Bernard

[Bernard Heathcote]

Hi Stu,

My understanding is that they also use a Richardson grating in the Shelyak eShel.

Cheers,
Bernard

[Hamish Barker]

Thanks Bernard,

Those are quite big gratings, I think I remember reading Uwe's article about transmission gratings, and I think his intention was to use transmission gratings in front of the telescope.

Considering the large ruled area, that price sounds reasonable. For something suiting our typical instruments circa 25x25 or 30x30mm, I'd expect the price to scale with the area, so maybe as little as 150-200 Euro? People certainly pay a lot more than that to change their camera to something with higher QE. So if they really are more efficient (say 10% conservatively, unless they really are much better), it sounds like a worthwhile investment compared to a better camera, or bigger aperture or better mount (better guiding = more photons on the slit).

Like most things, some quantitative measurement of product differences would be great (but a lot of work for someone).

[Bernard Heathcote]

Hamish,

Fully agree with your logic re price scaling to grating size. Unfortunately it appears the only way to get the prices is to ask for a quote.

Cheers,
Bernard

[Hamish Barker]

I see a really low dispersion option in their list, only 41lpmm, blazed for 500nm. Could be good for extending faint, low res performance down to mag 17+ SN candidates. there are a lot more of them than there are of mag 14-15 which is approximately my limit with 180lpmm grating in my L200 spectrograph.