healpix | convert between lonlat and HEALPix coordinates | 3D Animation library

Per the documentation of read_healpix_map():

ordering and coordsys are output arguments - they are pointers to space into which the function will write results. You have passed pointers to string constants in memory that will normally be marked read-only and may not be sufficiently large to receive the result in any case.

nside is also an output argument, initialising it to 512 serves no purpose. You do not need p_nside; you can simply pass &nside

It is not the most clear of interfaces; specifically it is not clear whether coordsys is a string or a single char. The documentation uses single quotes so you might assume char but then it does that for ordering too and that is clearly a string. It is safest to assume coordsys is a string - it will do no harm.

I think you're close. IMHO, this scatter plot is easier than plotting with both skyplot coordinates (projection="aitoff"). The process is similar to the answers I posted on your earlier question: Plot mean and standard dev values on skyplot using astropy from hdf5 file. You just need some minor teaks to the function parameters.

I modified your code to create a 2D scatter plot. Here's a quick summary of the differences:

• Changed from astropy.coordinates import SkyCoord (instead of HEALPix)
• Changed matplot type (removeprojection=)
• Changes y-variable from b_rad to faraday_sky_mean on scatter plot.
• Deleted c=faraday_sky_mean from plt.scatter() so data points are not color coded.

See code below.

After a lot of research I came to a solution for this problem:

First of all, I've changed the scheme to NESTED. With the NESTED scheme and a very high nSide value (8192), the returned value from the

As suggested, I can easily make use of the healpy.sphtfunc.smoothing function by specifying a custom (circular) beam window.

To compute the beam window, which was my problem, healpy.sphtfunc.beam2bl is very useful and simple in the case of a top-hat.

The appropriated l_max would roughly be 2*Nside but it can be smaller depending on specific maps. One could for example compute the angular power-spectra (the Cls) and check if it dampens for smaller l than l_max which could help gain some more time.

Thanks a lot to everyone who helped in the comments section!

In your Dockerfile, use :

Theta is co-latitude, Phi is longitude. It is confusing because their order is inverted than what we usually expect. In fact even in healpy, for example in pix2ang if you set lonlat to true, you get as outputs first Longitude and then Latitude. Unfortunately this is the convention and we have to stick to this.

Great question! I've written a short function to convert a catalogue into a HEALPix map of number counts:

In the below statement

The latter two values are "out" parameters, so you could call it by taking the address of stack-allocated variables.