Re: ITL Prayer Time

[Thamer Mahmoud <thamer at newkuwait dot org>]

abdulhaq writes:
 > Further to the discussions some time ago about the calculation of sunrise, 
 > sunset and noon times, I've had a bit of a hack of the libnova library that 
 > uses the VSOP87 calculation method. I've found that by removing a lot of 
 > unnecessary files (for us), I can get the libnova library down to 128k. This 
 > means that it's feasible to include this calculation technique, I think, in 
 > ITL. As it seems to me to be the most accurate method by some distance (it 
 > appears to be accurate to the nearest second), I would be far more 
 > comfortable using this as the underlying astronomical code.
 > 
 > So, would it be considered by yourselves as an option for inclusion in ITL 
 > (libnova is distributed under the LGPL licence)? Personally for kprayertime 
 > I would like to use ITL for the general algorithm and interface, but with 
 > this VSOP87 implementation.
 > 
 > و السلام
 > عبد الحقّ
 > abdulhaq


Salaam,

Actually, implementing a more standard (i.e. a simplified Sun-only
VSOP87) is one of the two significant changes that will happen before
0.6 release that I've talked about in another post. The other change
is not as significant though ;)

I would say that I'm 80% done so far. What's left is that I need to
implement a few remaingin formulas and a more accurate atmospheric
refraction code (so that we take advantage of pressure, temperature,
among other things). After that I'm going to add a new structure to
hold the data as well as convert the old Get[Salatname] functions to
use the new structure (and formulas).

Finally, If all went well with testing, I will be checking in the new
code. Just a note though, the new code will be, Inshallah, more
accurate than the formulas used currently on ITL-CVS, but please do
not expect that we will actually get the same exact results as
libnova, marsbase, or any of the other VSOP87 implementers. They both
claim to be using VSOP87 but their results differ by minutes as shown
here.


http://lists.arabeyes.org/archives/developer/2004/May/msg00000.html


By the way, Libnova does not use the full VSOP87, hence the small
size, but they use well known simplified formulas. These are the same
formulas that I'm currently implementing.


Regards,
Thamer Mahmoud