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Dec
22
awarded  Editor
Dec
22
revised How to get the longitude of the perihelion to find the Heliocentric Equatorial coordinates of a planet
Fixed typo in title
Dec
22
suggested approved edit on How to get the longitude of the perihelion to find the Heliocentric Equatorial coordinates of a planet
Dec
12
awarded  Commentator
Dec
12
comment How long does a sunrise or sunset take?
Actually, the ecliptic is the Sun's yearly path, not daily.
Nov
29
awarded  Yearling
Nov
28
answered When do Mercury/Venus reach greatest elevation at sunset/twilight for a given location?
Nov
28
answered Standard conditions for a heliacal rising
Nov
27
comment Equation for solar radiation at a given latitude on a given exoplanet?
Are you looking for a daily average/total (day+night) for midsummer and midwinter when the 'sun' is transiting, or for the insolation at any given time?
Oct
20
awarded  Yearling
Sep
24
awarded  Autobiographer
Aug
17
answered Is it possible for a person to not see the new moon at different places on earth?
Aug
15
comment What is star composition after formation
I think there may be confusion here between "a gas cloud reaches a critical mass/radius and collapses to form a star" and "the protostellar core reaches a critical temperatre and starts hydrogen fusion". See e.g. en.wikipedia.org/wiki/Jeans_instability for the former.
May
30
answered How to determine period of pulsar?
Jan
6
answered How to calculate Longitude from Right Ascension?
Jan
6
answered How to calculate the altitude of the Moon?
Nov
23
comment Can I see comet ISON from Saudi Arabia?
I added the code to libTheSky. This link points to github and my contact data in case you have questions. Check the functions best_planet_xsmag() and pl_xsmag() in the file visibility.f90 (it's in Fortran, sorry ;-)).
Nov
23
comment Can I see comet ISON from Saudi Arabia?
I use elements and magnitude data from the MPC - not perfect, especially for "first-time" comets. Still, the best moment for observation may suffer relatively little from systematic effects.
Nov
21
comment Can I see comet ISON from Saudi Arabia?
I apologise for the loss of format above (paste it into your text editor to restore the three columns). Summarised, the table indicates you could see ISON with the naked eye on Nov 17-21 and Dec 11-25, best around Dec 17 at 5:15 AST. The computer code is very simple and while I think that the best dates and times are roughly correct, the magnitudes are probably not and you may well need binoculars to see ISON as the original answer indicates.
Nov
21
comment Can I see comet ISON from Saudi Arabia?
Good, and I was wrong. I wrote a small program to compute exactly that: the "excess magnitude" defined as <limiting magnitude> - <comet magnitude corrected for airmass>, where positive values indicate you may see the object with the naked eye. I get (for Riyadh): Nov: Day time Exc.mag 15 4:56 -0.2 17 4:59 0.1 19 5:03 0.3 21 5:08 0.2 23 5:17 -0.4 25 5:53 -1.3 27 6:10 -2.2 (28 17:06 -50.7 - never visible) Dec: 01 6:15 -3.4 03 6:04 -2.3 05 5:57 -1.8 07 5:29 -1.3 09 5:23 -0.4 11 5:21 0.1 13 5:18 0.3 15 5:17 0.3 17 5:15 0.4 19 5:16 0.3 21 5:15 0.3 23 5:16 0.2 25 5:13 0.1 27 5:14 -0.0