[AstroPy] get_moon ... and the phase

[Tapio Pursimo]

Hello Eric,

Thanks!
The moon illumination is not really coordinate stuff, however for 
an optical astronomer it would be very handy to have the moon coordinates 
and illumination in one go.

Cheers,

   T a p i o


> Hi Tapio, 
> 
> Here’s how I handled this in some of my code: 
> 
> # Moon illumination formula from Meeus, “Astronomical
> # Algorithms".  Formulae 46.1 and 46.2 in the 1991 edition,
> # using the approximation cos(psi) \approx -cos(i).  Error
> # should be no more than 0.0014 (p. 316).
> 
> moon_illum =  0.5 * (1. - sin(dec_sun)*sin(dec_moon) -
> 				 cos(dec_sun)*cos(dec_moon)*
> 				 cos(ra_sun - ra_moon))
> 
> That gives the percent illumination of the moon, between 0 and 1. 
> 
>  If you can get the RA and Dec of the sun and moon, and the above 
> precision is good enough for your purposes, this is a simple way to do 
> it. 
> 
> Eric
> 
> 
> 
> > On Nov 29, 2019, at 7:38 AM, Tapio Pursimo <tpursimo at not.iac.es> wrote:
> > 
> > 
> > Hello,
> > 
> > Can anybody help me how to get the moon phase using astropy?
> > I can get the coordinates using get_moon, but the phase is apparently 
> > missing.
> > I would not like to use/install "ephem" nor "astroplan".
> > 
> > Best regards,
> > 
> > Tapio Pursimo
> > 
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>