Epoch 2 HST photometry at the location of AT 2023fhn, corrected for Galactic extinction, and fit to BPASS single age spectral models while allowing the (intrinsic) extinction to vary. Top row, left: the best fit single-age BPASS spectrum. Wavelengths are observer frame. The photometry was measured with median background subtraction and a 0.4 arcsec aperture, and is corrected for both Galactic and instrinsic extinction. Top row, right: the colourmap corresponds to the fit log₁₀(χ²) as a function of intrinsic extinction and age. We find a best fitting combination of Log(age/yr) = $8.2_{-2.2}^{+0.4}$ and A${}_{\mathrm{V}}=0.2_{-0.2}^{+1.8}$ (uncertainties at 68% confidence, Avni 1976). Pixels in the parameter space grid within the 68% and 90% confidence regions are indicated by crosses (within 68%) and dots (in the 68–90% range). Bottom row: as for the upper row, but using a 0.2 arcsec aperture for photometry, with which we find Log(age/yr) = $6.9_{-0.9}^{+1.8}$ and A${}_{\mathrm{V}}=1.6_{-1.6}^{+1.0}$.