Fiber scrambling for high-resolution spectrographs. I. Lick Observatory

TL;DR

This study demonstrates that fiber scramblers significantly enhance the stability of high-resolution spectrographs by reducing coupling errors, with double scramblers providing even greater improvements, especially addressing hour angle-related variations.

Contribution

First application of fiber scramblers at Lick Observatory's Hamilton spectrograph, showing improved stability and identifying pointing-dependent illumination as a key error source.

Findings

Fiber scramblers improve instrumental profile stability.

Double scramblers further reduce variability by a factor of 2.

Instrumental profile variations correlate with hour angle.

Abstract

In this paper, we report all results obtained with a fiber scrambler on the Hamilton spectrograph at Lick Observatory. We demonstrate an improvement in the stability of the instrumental profile using this fiber scrambler. Additionally, we present data obtained with a double scrambler that further improves the stability of the instrument by a factor 2. These results show that errors related to the coupling between the telescope and the spectrograph are the dominant source of instrumental profile variability at Lick Observatory. In particular, we show a strong correlation between instrumental profile variations and hour angle, most likely due to pointing-dependent illumination of the spectrograph optics.