Archive for 2014

Shared folder in linux

By grigoris | Filed in Astronomy

Suppose that we want to create a folder in which multiple users will have full access (which means that they will be able to read, write, and execute). We create the folder (under ‘/’ in this example, although it can be anywhere else): sudo mkdir test which has the following permissions: drwxr-xr-x 2 root root […]

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the end …

By grigoris | Filed in Astronomy

… and the start of a new chapter after the successful defense of the PhD on September 18th, 2014!

Since August 1, 2014, I have started working in the Stellar Physics Department of the Astronomical Institute of Academy of Sciences, in Czech Republic, with Michaela Kraus. I will contribute to the investigation of the mass-loss history of some massive beasts out there (Luminous Blue Variables, B[e] supergiants, yellow hypergiants) Information on these new area […]

Among the simplest installation methods to install IRAF are SciSoft (for RedHat/Fedora based distributions) and Fernando Avila Castro iso files (for Ubuntu/Debian based distributions). However, both require root privileges. What can you do when you do not have these permissions? Ureka [1] comes in rescue! It is easy to install (download and run the installer![2]) […]

Fast and easy conversion of a .reg file with image coordinates (x,y positions) to sky coordinates (RA,Dec;sexagesimal): ds9 image.fits -regions load input_imageCoordinates.reg -regions system wcs -regions skyformat sexagesimal -regions save outout_skyCoordinates.reg -exit with automatic exit of the program! Thanks to Alexandros M. for providing some examples! References: [1] ds9: http://ds9.si.edu/site/Home.html [2] ds9 command list: http://ds9.si.edu/ref/command.html

Retrieve header key with gethead

By grigoris | Filed in Astronomy

A quick note on gethead of WCSTools – as I have needed many times (but obviously not that many to remember it!). Rather straightforward use: gethead HEADER_KEY image.fits (as simple as possibly!) If HEADER_KEY contains empty spaces then use double quotes, e.g. “HIERARCH TEL AIRM END”. Reminder: you have to have installed already the WCSTools! […]

After a long time I finally managed to understand how to use IRAF’s sbands, along with a standard star and a filter. 1. If you want to use a spectrum from the standard star library of IRAF, you have to convert it from a .dat file to an image file .fits – Spectra files located […]

Struggling with BibTeX ???

By grigoris | Filed in Astronomy

Ok, it is time to try this promising thing called BibTeX [1,2,3], which allows you to use only one file with references* (suppose MyBibTeX.bib). Then, it easy to add references in any document just by simple adding the file and the citations. Although it seems rather straightforward hot to make the file its implementation is […]

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Complex dictionaries in python

By grigoris | Filed in Astronomy

How to make a dictionary of dictionaries with lists inside? For example we have a number of stellar spectral types (spec) and for each one of them we have a series of spectral lines (line) and their equivalent widths (ew). By creating a rather complex dictionary we can then call the list of values for […]

Although the are many information on how to use the genfromtxt (from numpy) there is not a clear demonstration (that I found…) to show how to easily read a text file with columns of data (including strings – it is straightforward to read columns of numbers with loadtxt for example). Suppose that we have the […]