Spectra extracted from 2 x PSF FWHM on the continuum position (top) of TMC1-W (top-left) and TMC1-E (top-right). The dashed blue line represents a polynomial fit to the continuum. optical depth as a function of wavelength resulting from dividing the polynomial fit with the observed continuum (bottom). The orange dashed line represents τ = 0. The range of extincition is calculated using optical depth value at the silicate feature following the equations: A_V = τ_9.7 × 18.5, and A_V = τ_9.7 × 9, representing the correlation found in diffuse ISM and galactic centre dense clouds, respectively (McClure 2009; Weingartner & Draine 2001; Chiar et al. 2007; Boogert et al. 2000).