Re: About the next version of DateTme::Event::Sunrise

What if you implemented it as 'spin' or 'hour' or 'spin_hour' or 
whatever, as a number and (optionally) exported constants to signify the 
algorithm? That means users could either provide their own number, or 
could use one of the provided.

I don't write much perl any more so forgive me if I get the syntax wrong 
here ...


     use DateTime::Event::Sunrise qw/SIDEREAL SCHLYTER/;

     my $sunriseset = DateTime::Event::Sunrise->new(
                      latitude  => 42.3358,
                      longitude => -71.2044,
                      altitude  => '-0.833',
                      precise   => 1,
                      hour      => SIDEREAL);


- Rick


On 6/20/2020 2:03 AM, Jean Forget wrote:
> Following the creation of RT ticket
> https://rt.cpan.org/Public/Bug/Display.html?id=132336
> I have decided to implement the proper precise algorithm in
> DateTime::Event::Sunrise (already implemented in Astro::Sunrise) and
> to check the values with NOAA's solar calculator and with Stellarium.
>
> After I have implemented the proper precise algorithm, there are still
> differences between the values obtained by Stellarium and the NOAA on
> one side and by DT::E::S on the other side. I have found that these
> differences are the caused by the "magic" values 15 and 15.04107 used
> in the module.
>
> 15.04107 is the angular speed of Earth's spin, while 15 is the
> combination of Earth's spin with the orbital speed of the
> Sun-Earth system. According to Paul Schlyter 's description of
> the precise algorithm, we should use 15.04107, but I have found
> that using 15 instead gives results closer to Stellarium.
>
> More abstractly, the problem is: when you are an low-level
> amateur astronomer, who is an authoritative source for you?
> Whom do you trust? Paul Schlyter or the Stellarium team or
> the NOAA?
>
> I have decided to defer this question to the module user. There is a
> new parameter, "algo", which lets the user choose between trusting
> Paul Schlyter more than Stellarium or trusting Stellarium more
> than Paul Schlyter.
>
> Now you may code either
>
>   my $sunriseset = DateTime::Event::Sunrise->new(
>                      latitude  => 42.3358,
>                      longitude => -71.2044,
>                      altitude  => '-0.833',
>                      precise   => 1,
>                      algo      => 'Schlyter');
>
> or
>
>   my $sunriseset = DateTime::Event::Sunrise->new(
>                      latitude  => 42.3358,
>                      longitude => -71.2044,
>                      altitude  => '-0.833',
>                      precise   => 1,
>                      algo      => 'Stellarium');
>
> Can you think of a better name for the new option? The creator of
> ticket 132336 suggests
>           spin => 15.04107,
> or
>           spin => 15,
>
> The problem is that the "magic" value 15.04107 is not easy to remember,
> especially if the module user knows even less astronomy than myself.
> While "Schlyter" and "Stellarium" are easier to remember.
>
> I will release the new version of DT::E::S to CPAN next week.
> If you have a better idea for the name of the new parameter, please
> tell me before this release.
>
> In the meantime, the updated code is available on Github.
>
> Thank you for your advice,
>
> By the way, this is the second attempt to write this message
> to the datetime mailing list. As it happened already, my first
> attempt was lost somewhere and did not reach you or the websites
> https://www.nntp.perl.org/group/perl.datetime/
> and https://www.mail-archive.com/[email protected]/.
>
> Jean Forget
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