As exoplanet characterisation relies on the detection of resolved features, analysis can be improved with high signal-to-noise ratios (SNR) that are possible to obtain with modern spectrographs like CRIRES+. However, obtaining high SNR through adjusting exposure times is trade-off that results in smearing of spectral features due to variable Doppler shift and in averaging blocked stellar radiation originating from different parts of the stellar disk. There is therefore a need to establish what the optimal compromise is between the SNR and time resolution for a given target. We will discuss potential approaches for establishing the optimal parameters for observing transiting exoplanets with spectroscopic instruments such as CRIRES+ using simulated spectra, cross-correlation, and other statistical methods. This will be particularly relevant for planning observational studies of close-in planets around cool stars with more complex stellar spectra.

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