Filters for NIR astronomical photometry: comparison of commercial IRWG filters and designs using OpenFilters

TL;DR

This paper compares commercial IRWG filters and designs new filters using OpenFilters software to improve NIR photometry accuracy with InGaAs detectors, aiding small and medium telescope observations.

Contribution

It introduces new filter designs tailored for InGaAs detectors and compares existing commercial filters to enhance NIR astronomical photometry.

Findings

Commercial filters approximate IRWG profiles with varying accuracy

New filter designs for InGaAs detectors are proposed

Potential for improved long-term NIR observations with new filters

Abstract

The photometric accuracy in the near-infrared (NIR) wavelength range (0.9 -2.6 microns) is strongly affected by the variability of atmospheric transmission. The Infrared Working Group (IRWG) has recommended filters that help alleviate this issue and provide a common standard of NIR filtersets across different observatories. However, accurate implementation of these filters are yet to be available to astronomers. In the meantime, InGaAs based detectors have emerged as a viable option for small and medium telescopes. The present work explores the combination of IRWG filtersets with InGaAs detectors. A few commercially available filtersets that approximate the IRWG profile are compared. Design of more accurate IRWG filtersets suitable for the InGaAs sensitivity range is undertaken using an open-source filter design software - OpeFilters. Along with the photometric filters iZ, iJ and iH, design of a few useful narrow band filters is also presented. These filters present opportunities for small and medium telescopes for dedicated long-term observation of interesting infrared sources.