Abstract:
Precision Doppler spectroscopy serves as an important tool for Radial Velocity (RV) measurements by observing
Doppler shift in the stellar spectrum, which are used for various applications. Passively stabilized Fabry-Perot
(FP) etalon based wavelength calibration is one of the techniques used for Doppler spectroscopy. The FP is kept
in a pressure and temperature-stabilized environment for it to produce equispaced transmission lines. Since the
FP is stable and the line shape is invariant across wavelength pass band, they can be used to determine the
spectrograph’s instrumental artifacts and hence analyze spectrograph performance. Knowledge of instrument
effects also helps in better prediction of the wavelength calibration model for the spectrograph. We have tested a
passively stabilized FP on Vainu Bappu Telescope (VBT) Echelle spectrograph and Hanle Echelle spectrograph
(HESP) and observed field curvature and distortion in both. We are analyzing the artifacts introduced and
correcting for the same using image processing methods to compensate for the same in wavelength calibration
model developed for the FP-based calibrator.
