Archive for February, 2010

Useful astronomical numbers

Posted February 19, 2010 By grigoris

Just some useful numbers and units to remember and to have an easy access to! [last updated: 29 Dec 2011] >> Distance 1 AU = 150 x 106 km 1 pc = 3.09 × 1013 km = 206260 AU = 3.26 ly 1 ly = 9.4 x 1012 km = 64 x 103 = 0.31 […]

About full Moon and Moon illusion

Posted February 13, 2010 By grigoris

The size of a Full Moon depends on the position of the Moon in its orbit (~ 0.5 degrees). Thus the biggest Full Moon is when the Moon is closest to Earth (i.e. at perigee). from (28 Jan 2010) “… a “perigee Moon” some 14% wider and 30% brighter than lesser full Moons of […]

A great image of star sizes

Posted February 12, 2010 By grigoris

A magnificent picture comparing star sizes !!! (from Wikipedia / Star – Diameter)

Moon (Lunar) phases

Posted February 12, 2010 By grigoris

Just a quick note for moon (or lunar) phases. From Wikipedia / Lunar Phases (moon phases). Phase Northern Hemisphere Southern Hemisphere Visibility New moon Not visible, traditionally Moon’s first visible crescent after sunset Waxing crescent moon . Right 1-49% visible Left 1-49% visible afternoon and post-dusk First quarter moon Right 50% visible Left 50% visible […]

40 characters limit in Starlink

Posted February 3, 2010 By grigoris

When you install Starlink you have to determine the directory of the program (set env starlink_dir /path/to/software/star, in the ~/.tcshrc file). Then, any application runs under this directory. But, there is a limit in the number of characters used (only 40). This can cause some programs not to run at all or run very quickly […]

While loop in C-shell scripts

Posted February 3, 2010 By grigoris

When using the while loop in C-shell scripting the usual stucture is: while (expression)commands…end BUT, you need to add an empty line or a comment after end in order for the loop to work!