Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Random dither offsets applied to fibers should be constant as a function of wavelength #108

Open
schlafly opened this issue Nov 6, 2019 · 0 comments

Comments

@schlafly
Copy link

schlafly commented Nov 6, 2019

Currently specsim applies a random fiber offset when simulating spectra. This offset is configurable in

sigma1d: 5.22 um

At the moment, this random fiber offset is applied independently at each wavelength. get_focal_plane_optics loops over wavelength, calling get_centroid_offset, eventually calling
def offset_function(angle_x, angle_y, wlen,

and applying a different random offset to each wavelength.

I didn't immediately see a clean API change to fix this. Perhaps get_focal_plane_optics should call get_centroid_offsets out of the loop, and then offset_function should be taught how to broadcast over the wavelength axis. But at the moment I thought I'd just file an issue.

Not clear to me that this has practical impact---it seems to me like the fraction of flux will go something like (offset/FWHM)^2, so roughly 0.25% multiplicative noise at each wavelength?

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Labels
None yet
Projects
None yet
Development

No branches or pull requests

1 participant