In 1847, he installed a five-foot achromatic telescope by Dollond, mounted equatorially, in a small observatory he built for the purpose in his garden.
With the help of a transit circle by Jones and of the Beaufoy clock, lent by the Royal Astronomical Society, he very accurately determined the time, and supplied it during many years to the ships leaving Southampton.
At the Southampton meeting of the British Association in 1846, Drew was appointed one of the secretaries of the mathematical section, and printed for the use of the association a pamphlet ‘On the Objects worthy of Attention in an Excursion round the Isle of Wight, including an Account of the Geological Formations as exhibited in the Sections along the Coast’.
Between 1848 and 1853, he took systematic meteorological observations, and summarised the results in two papers on the ‘Climate of Southampton’, read before the British Association in 1851 and 1854 respectively.
His last work was a set of astronomical diagrams, published by the Department of Science and Art in 1857, representing the moon, planets, starclusters, nebulæ, and other celestial objects.