Forum der Vereinigung der Sternfreunde

Forum of the German Amateur Astronomy Association
Aktuelle Zeit: 19. März 2019, 03:41:02 AM

Alle Zeiten sind UTC+02:00

Ein neues Thema erstellen  Auf das Thema antworten  [ 1 Beitrag ] 
Autor Nachricht
 Betreff des Beitrags: Automated measurements
BeitragVerfasst: 27. Dezember 2018, 16:06:24 PM 

Registriert: 06. Oktober 2016, 15:04:43 PM
Beiträge: 204
Hi all!

Since we have now some more spectra, (thank you to all contributors!) we started some work on automating the measurements.

In particular we are working on a ESO-MIDAS script for radial velocitys, fwhm and line minima/maxima (for calculating ratios → Teff). It is developed for working on single lines. Maybe in the future we want let it measure more lines in one run. But first we have to test the quality of the data output!

We did some comparisons between our by eye and hand measured data and data out of the script. It may be that the script is working at a relative good level.

Here are some comparison graphs:

image (1).png
image (1).png [ 30.74 KiB | 197 mal betrachtet ]

We have implemented two options: One is to measure/read the line depth by the lowest pixel found with the MIDAS command statis/imag. The other is to use the gaussian fit. The second method we assume will work slightly better in spectra with low snr or emission lines which are disturbed by absorption (tellurics...).

image (2).png
image (2).png [ 31.91 KiB | 197 mal betrachtet ]
The rv measurement is also based on gaussian fits and can be adjusted in the integration range. It seems that using the whole line (about factor 1) leads to the most little scatter. (We used the FeII 6443 for this test. The also by script measured Si II 6347 looks less disturbed in the spectra.)
But if lines are disturbed there is of course more scatter. Like you can see at begin and end (time scale) at the graph.
Do anyone have ideas to improve the accuracy on disturbed lines (Due to star spots… etc)? Would for example a x-correlation on that small wavelength range with only one line help? As template maybe could serve a good (Bisector-method tested) line from our data sample?!

Malin and Christoph

Nach oben
Beiträge der letzten Zeit anzeigen:  Sortiere nach  
Ein neues Thema erstellen  Auf das Thema antworten  [ 1 Beitrag ] 

Alle Zeiten sind UTC+02:00

Wer ist online?

Mitglieder in diesem Forum: 0 Mitglieder und 1 Gast

Du darfst keine neuen Themen in diesem Forum erstellen.
Du darfst keine Antworten zu Themen in diesem Forum erstellen.
Du darfst deine Beiträge in diesem Forum nicht ändern.
Du darfst deine Beiträge in diesem Forum nicht löschen.
Du darfst keine Dateianhänge in diesem Forum erstellen.

Suche nach:
Gehe zu:  
Powered by phpBB® Forum Software © phpBB Limited
Deutsche Übersetzung durch