(Partial answer - and a bit long winded)
Regarding comparable telescopes - source : The Herschel Objects and How to Observe Them, by James Mullaney.
Herschel's telescopes far surpassed in both quality and size any other telescope in the world at the time. After comparative trials at a number of observatories in England including Greenwich, he stated ...
The best answer to that question is the following book:
The steam engine of Thomas Newcomen
by L. T. C. Rolt, J. S. Allen
Moorland Pub. Co. ; New York : Science History Publications,
To summarize what I learned from this book.
The boilers did not generate enough steam pressure to move pistons. You needed to use the weight of the atmosphere for the ...