spectro-aras.com

RE:"Une mise à jour assez complète de ma page sur l'optimisation de eShel :

http://www.astrosurf.com/buil/asi6200mm/

(but still in French for the moment, really sorry)."

I had Microsoft Edge make a English translation and output to .PDF for us "French" challenged eShel fans!
http://astroimage.info/files/eShel%20an ... 20ENG2.pdf

James

Great stuff James,

Thanks for taking the time to put that up.

Another fantastic essay from Christian too!

Regards,

Stu

Thanks James!

Tom, some out of the topic, but... here a part of my presentation for the ASW2020 Spectroscopy Workshop, the November 8:





An excellent solution also for Lhires III spectrograph, I confirm.

Christian Buil

Most interesting,

Most interesting, thankyou Christian, as always! I think this confirms my view that a fast newtonian has a lot to recommend it.

The AAVSO workshop has some really fascinating presentations, but the time of day is terrible for this side of the world (this isn't a complaint - I know you can't accommodate everybody with one time), so for Australians and New Zealanders it's probably best to wait until they put up the recordings of the sessions afterwards.

Thank you for the APM 2.7x Barlow test, Christian!
So the 65mm backfocus (yellow arrows in the picture) is your modified recommendation in order to achieve 2x rather than 2.67x ? (APM specs saying "Backfocus: 105 mm from Center last Lens" and "Resulting focal length: - 62.9 mm")
Peter

Yes Peter, the change from 105 mm to 65 mm is to achieve the 2x. The Barlow work well at 2.7x but also at 2x (my optical simulation and test on the sky) at the center of the field.

Christian

Bonjour Christian,
The results that you have achieved are really spectacular, incredible to do times ago, congratulations for that !
With this system you make observations with hardly any noise in them and I need 5 times more time than you for similar results !

You know that most of the echelle observers we use in our instruments the ATIK460EX that you know very well. One "little" problem is the price of these cameras that have the IMX 455, so many of us will use the ATIK for a few or long time.

But following your instructions, I have made this Vega target with a reduction test by CMOS system with hopeful results.
 
Telescope Schmidt-Cassegrain. ATIK460EX, ISIS 6.03                     

Phase 1 : All frames in binning 1x1                                      

Phase 2 : 7 Vega frames, Thor and Tung pretraitement- make BIAS and DARK  subtraction, ( I have not known how make the FLAT ).                                       
Phase 3 : 7 Vega frames, Thor and Tung have passed for CMOS treatment, median filter 5x5 and binning 2x2.
                   
Phase 4 : Classic treatment with ISIS 6.03,  "Function de blaze lisseé" and "Order merging adjustment" activated.

Have I followed the appropriate way ? Is it possible to achieve good results with our ATIK460EX with this reduction system ?I think there are three many problems, the resolution down from 10000 to 8000, ripples appeared in some regions and it is possible that the noise in the violet could be improved.
What is your opinion about that ?

Cordialement, Joan.

Hello Joan,

I don't understand why you want to proceed CCD data with a CMOS process ?

CMED in ISIS V6 is only for a CMOS camera because CMOS camera have telegraph noise, not CCD.

It's normal that you decrease resolution of your spectrum with CMED process because you use a median filter and binning factor on your raw images.
With an ATIK 460ex your pixel size is 4,54µm, with the CMED process your pixel size grow at 9,08 µm
With an IMX 455 the pixels size is 3,8µm, with the CMED process your pixel size grow at 7,6 µm

The best process to reduce CCD data is the "classical" method.

Joan Guarro Flo wrote:Bonjour Christian,

With this system you make observations with hardly any noise in them and I need 5 times more time than you for similar results !

I cannot believe a change from CCD to CMOS with different processing can make that much difference. The must be some other problem (or "magic" !) here

Cheers
Robin