Forum der Vereinigung der Sternfreunde

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PostPosted: 06. October 2016, 14:04:41 PM 

Joined: 23. February 2008, 19:33:52 PM
Posts: 100

I decided to undertake a project to attempt observing the full period of a binary star, with full coverage of that period, plot the result, make some calculations on the orbit and mass of the stars!
I had done nothing like this yet, so I devoted my efforts to "how all the data would be processed with only the usual tools I use".
In a sense this project is more to teach me ways of coping with the data, and not so much to actually do something 100% correctly... I did learn a few things about the quality of the observations, and I am considering redoing a lot of observations to get better guiding, and choose better spectra.
This project started 3 months ago, and I planned on observing multiple stars, but I ended up sticking with only one for now. I chose delta Capricorni. It is 2 degrees away from the ecliptic, and in 3 months the radial velocity of the Earth changes a lot and must be taken into account.
The spectra vary in exposure time, in telescope used, in CCD cooling temperature, central wavelength... This made me lazy and skip the pre-processing steps of darkframes, flat frames, response curve corrections... (I am waiting for my Lhires upgrade to arrive, to do this better next time)

Even so, I am proud of the result! It is "crappy", and preliminary, but I was able to create and follow a procedure that can combine 1D graphical spectra in a plot by phase! All this using only IRIS and a spreadsheet program (including making the spreadsheet generate the appropriate scripts that are run in IRIS). This procedure took me one week to get working, but allows me to process 3 months of data relatively quickly! So now I only need to get good data, and pre-process it decently :)
File comment: H-alpha radial velocity variation along orbital phase for delta Capricorni
delCap_phaseplot.jpg [ 39.89 KiB | Viewed 331 times ]
del Cap has a period of 1.0228 days, which is so close to 1 day, that I need to observe it for 4 weeks to register the complete period from the same location. Add your availability on weekends, bad weather, desire for other targets, and now you need a good spreadsheet to plan your observations! :arrow: This was step one.

:arrow: Step two involved keeping up with the observations already made, and which parts of the orbital period were still missing observations.

:arrow: Step three was to be able to sort the files according to phase, and to make the spreadsheet generate the script that automatically averages/bins redundant spectra of the same phase! (this involves generating a script to query for the heliocentric corrections needed, and perform such corrections on the acquired spectra)

When my Lhires is upgraded, I will redo this for another EA/EB-binary of the winter sky, but I need not limit myself to such targets. This is something I can use for long term observation projects: the real purpose behind it :!: The EA-Binary is only the application that motivates me to "develop" the rest :)


PostPosted: 06. October 2016, 14:42:11 PM 
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Joined: 31. July 2006, 16:43:32 PM
Posts: 3417
Location: Köln
Absolutely great, Fil!
That is a prototype example for how to start learning a new procedure and will encourage the Mizar gang in Germany (Ulrich, Bernd, ...) to finally present their experiences. :wink:
Cherio, Thomas

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