In message , Peter Bull
writes
having seen the picture of the day today at
http://antwrp.gsfc.nasa.gov/apod/astropix.html
I wondered is there is any discernible expansion
showing between the oldest photos taken
and ones taken now?

There should be. The Crab is relatively young (950y) and was probably
more compact and brighter when Messier catalogued it. Optical images
should be available for the past century. You may also find more recent
radio observations at sufficiently high resolution and time baseline to
show secular motion of knots and changes within it.

Certainly such data exists for the expansion of the radio SNR Cassiopeia
A which is younger (~300y) and so expanding faster - easier to measure.

Regards,
--
Martin Brown