Sarah Williams' lyrics "Though my soul may set in darkness" from her poem "The Old Astronomer" were set to music with a nice melody. See this YouTube video, for example. The melody is attributed to Franz Joseph Haydn.
Which Haydn piece was this melody taken from?
Searching the web only resulted in sites that show "Though my soul..." linked to Haydn, but without naming the underlying piece. Searching the melody on Musipedia.org had no satisfying results either.
Does anyone more familiar with Haydn's work recognise the melody?