Forum der Vereinigung der Sternfreunde

Hallo,

As you already know, "modal noise" is an inherent problem in all spectroscopes that use fiber optics. Andrew Smith, Christian Buil and others have applied very good solutions to their echelles. Their results have been really unbeatable.

Now I present my option to solve the problem, you will find it at, https://www.youtube.com/watch?v=F_klNTh ... e=youtu.be
Possibly the results can be improved ..., I leave two graphs of the star Vega where the differences are noticed using the agitator.

Regards, Joan.

Hi,
interesting , what is the number of ADU after an exposure of 20 seconds from vega with and without agitated tor, what is your CCD camera, what is the diameter of your telescope?

I have on other question:

I have the new colli from shelyak for the eShel. I use ISIS. But if I reduce higher orders then 51 the merging will not run . The xxxxxfull.fit has only zeros for the intensity and nothing is to see. But I can plot the orders 51,52,53 , but I cannot create a fully merged spectrum from order 33 to 53. Do you have a idea, what I could do?

The merging is running if I select orders from 33 to 51, not selecting 33 to 53

Berthold

Berthold, I would ask o the ARAS forum as it is probably an ISIS issue and Christien Buil will see it there.

The merged spectrum is lowered resolution than the I individual orders and for cosmetic rather than scientific use.
Regards Andrew

Hi Joan, according to my information the agitator movement should be non-harmonic to reduce fiber noise best. You device, however, introduces a harmonic movement with a strikt period. Hence, it is perhaps possible to reduce noise even further, even if you use only two of the upper rotation arms having a different frequency to the lower one.
Cheers, Thomas

Hallo Berthold,

I have SC16" telescope, in two different place, reduced to 6.3 by Alan Gee Mark II, two echelle spectrograf build myself the MUSSOL and the LINX, with a ATIK460EX CCD cameras.
For these observations Vega, ADU them about 45000, ( on 65535 ). The problem isn't the ADU. The problem is the "Modal Noise".

The "modal noise" is nonexistent for a telescopes to F/3.5 and it's very big for a F/10.

I leave these adresses,

https://arxiv.org/pdf/1802.01642.pdf

https://arxiv.org/ftp/arxiv/papers/1209/1209.2906.pdf

You can find more a lot of information by Internet about this problem.

You can find to practic solutions in,

http://www.spectro-aras.com/forum/viewt ... f=8&t=2031

http://www.spectro-aras.com/forum/viewt ... f=8&t=1965

http://www.spectro-aras.com/forum/viewt ... f=8&t=2013

And highly recommended,

http://www.astrosurf.com/buil/modal_noise/

It exist a diference from the eShel to LINX and MUSSOL spectrographs, the eShel use a prism with a cross disperser, instead to transmision gratings in my echelles. The resultant image is different becouse I use the ISIS. But you can try to reduce the value of "Detection threshold", if it not result, how Andrew says, you'll expose this problem in the Aras Forum, sure exist an easy solution.

To make the flats, C. Buil uses a 4700K tungsten bulb, I do not know if this can also help.

Hallo Thomas,

Many thanks for your information, it's one posibility, other is try to vary the speed of rotation, I don't know...We'll see how I can do...

Regards to all, Joan.

Hi Joan,

thank you !

first:

I am interested for a single frame of vega and the maximum of ADU you get then.......Knowing this value, and knowing the diameter of your telescop and the name of your CCD I can compute the total efficiency of your equipment and so I can compare.......

second:

my merging problem I belive not, that it is a flat problem, but I don't know this. I use "detrction threshold of 100......and....nothing is going on.

The problem : all orders from 33 to 50 are normalized to 1 not so the orders 51,52,53......please see adnexe. This cannot go on with merging, but why?

Amicalemet
Berthold

Hallo Berthold,

If you have well the files "def_order.list", "def_lambda.list" and "lines.list", look if in the "Settings" all are correct.

I think that Olivier Garde can be a great help. Sure the problem it's a bit silly...

I hope with curiosity tle solution.

Amicalment, Joan.

Hallo Berthold,

Have you been able to solve the problem? How is the "check2.fit"? I could try to help you, but you should send me all the information to my email, jngrrfl@gmail.com. You could use the "wetransfer.com".

Then I will configure the ISIS with your setup and I will try to see what happens ...

Do not worry, I have sometimes sent messages to Aras and no one has answered me. Maybe it's too early ...

Regards, Joan.

Hi Joan

many thanks, and, indeed there is no answer incoming from Aras. But in time I could solve the problem by myself, I got a hint from Martin Dubs: the orders 51,52 and 53 must be extended in the file " def_order.lst". This was the problem and I didn't know this......

Now once more:

Could you take a spectrum from vega of TWENTY seconds please? Could you please send me the 1D and the 2D Spektrum please.

Amicalement
Berthold

By the way: What is your mother language, exists anywhere some pictures from your echelle spectrographs?

Hallo Berthold,


The behaviour of the Aras Forum members sometimes it's a bit rare. If they see you ask one easy question, or it's of simple solution, they don't ansewring. They prefer that you finding it yourself...I've also been through this situation many times.

Marin Dubs is a really a great specialist, he knows a lot of spectroscopy, and ever is ready to help to everyone. If my echelles work, is thanks by Martin.

It was two last nights cloudy here, I can't give Vega 20 seconds exposure becouse the CCD image is saturated. I leave here, an image CCD of Vega, a Vega's graphic and other of the light-day.

I don't know if is that you ask to me, but here you can find pictures wiht the Linx in construction.

viewtopic.php?f=2&t=4681

viewtopic.php?f=4&t=4863&p=30070#p30070

viewtopic.php?f=28&t=4449&p=28898#p28898

viewtopic.php?f=32&t=4451&p=28166#p28166

My mother language is the Catalan, at present, we speak about 10 million people, distributed in Catalonia, the Valencian Country, the Balearic Islands, Andorra, and also in France, Vallespir and Rosellò, and also in the small city of Alghero on the island of Sardinia. In spite of not having any state that protects us, Catalan is the twenty language used on the Internet World and also was one of the first European languages to have grammar, in our language there are words of Germanic origin, for example "blau" that is 'writes and is pronounced as in German language.

We are a small town with more than 1000 years of history, even when we dominated the whole of the Maditerra Sea for some years. A few months ago in Germany, I had retained Carles Puigdemont, our President, who by the way, have treated very well.

I apologize to everyone, if I were too much.

The modal noise only affects the "flat" areas of the blue and white stars, in the other stars (if there is a good ADU), it can work perfectly without agitators. In blue and white it is absolutely necessary.

Best Wishes, Joan.

Hi Joan

Thank you , Klaus Vollmann has found , your total efficiency is about 8-9%, I have had 8,3 before changing the collimator.

I loose ~ 50% of light in my fiberinjection (shelyak) . How does it look with your fiberinjection? Do you have any Foto from your fiberinjectiuon?

cheers
berthold

Hallo Berthold,

Sorry but I don't know what to answer you. I did the my first echelle, ( MUSSOL ) to "direct injection", without fiber, but the results went very inestables and unacceptable. The solution was the optical fiber, The MUSSOL went very well and that's it. I wasn't do any study about the optical fiber and not either had another alternative..

I send a picture if it's useful for something..

Friendly, Joan.

Hi Joan, thank you.

It's ok so.

I would like to give you all the files, so you could try to reduce my frames(?) please.

Could I use the Dropbox ?

Friendly
Berthold

Hallo Berthold,

You can send me your files by Dropbox, I don't have any problem.

For your information, I always use the ATIK460EX with bining 2x2 , same do Olivier too.

Regards, Joan.