about Grigoris Maravelias
Year: <span>2011</span>

Year: 2011

Closest O type stars

Reading the book of F.D. Seward and P.A. Charles, “Exploring the X-ray Universe”, I found out some really massive and luminous O type stars that are close by and can be pointed out easily at the night sky: star distance (kpc) magnitude (V) spectral type ζ Pup 0.44 2.3 O4If …

About licensing

Stumbled upon the various different licenses I though to write down some conclusions (if I really got into any…). A nice comparison table of free software licenses is given in the Wikipedia where it is easily to see which licenses allow: (i) the link with other licenses and (ii) releasing …

IRAF’s error message 502 and pixel value replacement

While running a data reduction of IR observations with IRAF, the ccdproc printed this error: ERROR (502, “floating point invalid operation”) which means that some values of the image used (the flat image in this case) are not suitable for the performing mathematical actions (like division with 0s). Moreover the …

Buggy behaviour of unpack within numpy.loadtxt

The routine loadtxt from numpy (numpy.loadtxt) can be used to load columns of data from various files. This works great as long as numbers exist and becomes buggy with strings. Suppose we have a file (named ‘test.test’) with these values: 3103725. 1616.93596535 13.656 0 2011-05-23T23:49:35 3139474. 1405.95436047 13.643 0 2011-05-23T23:51:16 …