Forum der Vereinigung der Sternfreunde

Hallo,


The image shows the graphs of two observations of the star V694Mon, one is made by Umberto Sollecchia from L'Aquila (Italy) and the second one is made with the REMO telescope, from Sta. Maria.

The used telescopes and spectrographs are completely different, so is the spectral resolution. But the two graphs coincide, (I have not manipulated or adjusted, I have compared only two).

This means that the method of treatment we use, based on the ISIS by C. Buil, seems to work in a very acceptable way. I'm happy.

Joan.

Hello Joan,
are both spectra processed with Isis? It looks strange that the blue lines below 6550 A are stronger than the the red lines but the blue Ha is weaker than the red one. Is V694 MON a variable star? If yes are both spectra taken at the same time?
regards
Christian

Hallo Christian,

The two spectra were processed separately, U.Sollecchia sued and I sued, both with ISIS. The small differences below 6500 A. could have several causes, one of them, is the different resolution of the two spectrographs. V694 Mon is a symbiotic variable star, a spectral type (a bit complicated), it is M4ep + Bep. As indicated above the image's right, the difference between them is around 24 hours.

Also, the result of the graphics is due to the processing of CCD "images" (in all cases, the star's light is "transformed", the process is a bit more "complicated", for example, photometric observations where the intensity of the stars is measured directly from the CCD images of the stars).

In spite of all, the precision that we, with our devices and methods is +/-3%, this accuracy is practically the same, that I (a few years ago), obtained when doing CCD photometry with filter V. Measuring the characteristics of the graphs of the different observers, it provides a very reliable medium, that's all we can do.

The two spectra were processed separately, U.Sollecchia sued and I sued, both with ISIS. The small differences below 6500 A. could have several causes, one of them, is the different resolution of the two spectra. V694 Mon is a symbiotic variable star, a spectral type (a bit complicated), it is M4ep + Bep. As indicated above the image's right, the difference between them is around 24 hours.

Also, the result of the graphics is due to the processing of CCD "images" (in all cases, the star's light is "transformed", the process is a bit more "complicated", for example, photometric observations where the intensity of the stars is measured directly from the CCD images of the stars).

In spite of all, the precision that we, with our devices and methods is + -3%, this accuracy is practically the same, that I (a few years ago), obtained when doing CCD photometry with F plugin. Measuring the characteristics of the graphs of the different observers, it provides a very reliable medium, that's all we can do.

I think these images are quite eloquent.

Friendly, Joan.

Hello Joan,
in my opinion the only way to proof the reliability of Isis is to process several spectra with Isis and with an other widely accepted software i. e. Iraf or Midas.
Cheers
Christian

Christian, I did do a simple comparison using LHIRES III data from Robin Leadbeater. I did not do a full test as I was trying to see if I could get IRAF to work having used ISIS in the past. I found the extractions were identical but for a one pixel shift well know in ISIS.
The thread on ARAS is here http://www.spectro-aras.com/forum/viewt ... f=8&t=1690. This was using the the long slit IRAF and ISIS LHIRES III process not the echelle process.

REgards Andrew

Hallo Christian, Hello Andrew,

When this February 12th, I started this new topic, my intention was not to question the reliability of the ISIS. But it was to explain a small positive confirmation of our methods of observation.

I am not the only I use the ISIS, the observers of the ArasForum and those registered in the BeSS (Observatory of Paris), only last year, we treated thousands of specters, with the ISIS (myself, about 800 observations , which represent about 6000 CCD images, moreover images of darks, bias, flats and calibration lights), a part of these works by all observers have been used to publish studies and articles, for example in "Astronomy and Astrophysics ".

I do not know any author of the studies published in these professional journals, which rejected a single graphic treated with ISIS. At the moment I will not spend my time trying to learn to run the IRAF or MIDAS, I do not see it necessary.

When I speak of precision errors between +/- 3%, these errors are produced, for the telescope, the spectrograph, the conditions of the sky, the CCD and the observer themselves. Many professional observatories would want to have this degree of reliability. We are human and perfection we can only smell it.

Friendly, Joan.

Hello Joan,

Is there a interest to compare the results with an total different data reduction process? So I can offer you to handle your frames with Midas. It would be interesting to know whether differences arise from this.
If you want please send me all the frames of this series, which are needed for the evaluation.

_________________
Herzliche Grüße / best regards

Lothar

https://lotharschanne.wordpress.com/

Joan,
Likewise I can offer to process data with the latest BASS software.
Let me know if I can assist.

_________________
" Astronomical Spectroscopy for Amateurs" - Springer

Dear Lothar and Ken,

Usually I do 10 images for each star to obser. I have compressed the observations of VV Cep, along with other files that I think I might need. The first, it weighs 24169 kB, the second with 5 images of the VV Cep, it weighs 15219 kB.

Which one do you want? Send me your emails to jngrrfl@gmail.com, and I will send you the FIT.

So far I don't have any reasonable doubt to good operability of the ISIS. This software is very fine. The thousand of observations processed with it so they show it.

Here, http://www.astrosurf.com/aras/Aras_Data ... /VVCep.htm , are 550 spectra of the VV Cep, of which 367 are obtained since the beginning of 2017. I think that Olivier THIZY has to take the last observations, of course, each observation is scrupulously analyzed before being admitted in the database. All these graphics have been processed with ISIS. These graphics are available to everyone.

Friendly, Joan.