[AstroPy] Enquiry about origin change in wcs.all_world2pix

[Partha Sarathi Pal]

Hi,
 I have a query about wcs.all_world2pix
I am trying to make a skymap plot. see the attached files.
I made the wcs projection. In wcs projection origin is taken as lower
left corner.
Now I want to plot some coordinates on skymap with wcs.all_world2pix
command.  see the magenta and white diamond in the plot.

starloc = wcs.all_world2pix([[Ra_obj, Dec_obj]],0,maxiter=20,
tolerance=1.0e-4, adaptive=False, detect_divergence=False,
quiet=False)

https://docs.astropy.org/en/stable/api/astropy.wcs.WCS.html#astropy.wcs.WCS.all_world2pix
see this link/ screen shot.
The origin is upper left in all_world2pix code.  In wcs plot or skymap
plot origin is lower left corner.

This can give wrong value of coordinates to pixels.
For this reason some standard sources are placed in different places.

Am I correct?
Partha

-- 
Partha Sarathi Pal
Room No- 106, Haibinhonglou - 18
School of Physics & Astrophysics
Sun Yat Sen University, Zhuhai Campus
Da Xue Lu, Tangjia, Zhuhai,
Guangdong, 519082, China
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