Hi Wei-Hao,
“For the orientation, now I can see why the image in the previous screen shot is tilted. Among all the panels, one is tilted relative to the Galactic plane, and that one happened to be picked by APP as the reference.”
Murphy’s Law I guess… ?
“To be clear, after I launch APP, its icon appears immediately, but it takes 2 to 3 minutes for the processing window to show up. ”
Okay, i’ll put it on the RFC list to investigate, i’ll check my server logs as well. Strange behaviour indeed.
“Finally, will the equirectangular projection project the 2pi sky into a sphere or a rectangle?”
The equirectangular projection maps your data in longitude and latitude. Currently the [0,0] coordinate of the projection is the center of the reference frame. So this has some influence on how the projection actually looks.
How the 2pi sky turns out, depends on several things. Is your data a semi-sphere? Or is it a circle on the sphere? In the latter case, possibly a cylindrical projection would be nice.
To give you an idea, what will happen with the equirectangular projection versus the rectilinear projection, I show the same image with different projections, field of view is 180 degrees x 60 degrees (give or take) from the northern to southern horizon. Data is courtesy of Ralph Wagter. Canon 6D with a samyang 14mm f/2.8 objective
first image is rectilinear, straight lines stay straight, but perspective distortion is a real problem as you can see.
second image is equirectangular, now the data can easily be projected. A square rectilinear image, becomes more a circle under the equirectangular projection.
Cheers,
Mabula
