6 million light years by detecting Cepheid variables. This coincides well with the value for other Virgo galaxies, including M100 . The difference of their to our value is mainly due to another distance of the Large Magellanic Cloud assumed by them - the Hipparcos correction would increase their distance to about 58 Mly. For the moderately equipped amateur, M91 is one of the most difficult Messier objects. Suggestions of this bar may be seen at medium power even in smaller telescopes, if the viewing conditions are good enough to see the galaxy at all.
Photos show the bar more clearly, and show the spiral arms emanating from the ends of the bar.
This effect can be reproduced to some degree with amateur instruments.