obstools.deveny_grangle module
DeVeny Grating Angle Calculator Module
LDTObserverTools contains python ports of various LDT Observer Tools
Lowell Discovery Telescope (Lowell Observatory: Flagstaff, AZ) https://lowell.edu
This file contains the deveny_grangle routine for computing the needed grating
tilt angle to be set in order to center the desired wavelength on the CCD.
Both a CLI (direct copy of the IDL version) and GUI version are included here.
- class obstools.deveny_grangle.DevenyGrangle[source]
Bases:
ScriptBaseScript class for
deveny_grangletoolScript structure borrowed from
pypeit.scripts.scriptbase.ScriptBase.- classmethod get_parser(width=None)[source]
Construct the command-line argument parser.
- Parameters:
description (
str, optional) – A short description of the purpose of the script.width (
int, optional) – Restrict the width of the formatted help output to be no longer than this number of characters, if possible given the help formatter. If None, the width is the same as the terminal width.formatter (
HelpFormatter) – Class used to format the help output.
- Returns:
ArgumentParser– Command-line interpreter.
- obstools.deveny_grangle.compute_grangle(lpmm: float, wavelen: float)[source]
Compute the needed grating angle
Given the grating’s line density and the desired central wavelength, compute the required grating angle. Uses
scipy.optimize.newton()as the root-solver.
- obstools.deveny_grangle.deveny_amag(grangle: float) float[source]
Compute the anamorphic demagnification of the slit
The rays hitting the grating in the plane of α and β diffract to the camera in such a way that the beam width changes as a function of α and β, whereas rays incident on the grating in the perpendicular plane have the same beam width upon incidence and reflection. Because there is a difference between the beam widths for the two planes, there will be different magnification levels (Schweizer, 1979). Whenever perpendicular planes have different magnifications, this is called “anamorphic” (de)magnification. Schweizer (1979), however, thinks the term “anamorphic magnification” is somewhat inaccurate, and prefers “grating magnification”. Historically, the DeVeny manuals and associated code (e.g.,
deveny_grangle) use “anamorphic”, so we continue that there. The resulting magnification in the direction of dispersion due to the grating, r, arising from differentiation of the grating equation, is:\[r \equiv \frac{dβ}{dα} = \frac{cos α}{cosβ}\](Schweizer, 1979). Practical spectrograph design aligns the slit perpendicular to the dispersion direction, and so the change in magnification is in the direction of the slit width, hence our quoted “anamorphic demagnification of slit width”.
- obstools.deveny_grangle.deveny_grangle_cli()[source]
Compute the desired grating angle given grating and central wavelength
Command line version of
deveny_grangle, direct port of the IDL version. Takes no arguments, returns nothing, and prints output to screen.
- obstools.deveny_grangle.deveny_grangle_gui(max_gui: bool = False)[source]
Main Driver for the DeVeny Grangle GUI
Compute the desired grating angle given grating and central wavelength
GUI version of
deveny_granglebuilt usingPySimpleGUI. The GUI includes a drop-down menu for available gratings, and checks for a requested wavelength between 3000A and 11,000A. This interface uses the same subroutines as the CLI version and produces the same results.This version optionally allows for the calcuation of the central wavelength given a grating angle
- Parameters:
max_gui (
bool, optional) – Display the MAX GUI (forward and backward calculations) (Default: False)
- obstools.deveny_grangle.grangle_eqn(theta: float, lpmm: float, wavelen: float) float[source]
The grating equation used to find the angle
This is the equation for which
scipy.optimize.newton()is finding the root.