Two observations in my log, most recently in april 2015 under dark Alpine skies. 14" SCT @ 168x / 29':

Quite a faint NE-SW elongated glow with a bright nucleus that is visible without AV. With AV subtly brighter in a very small core that is slightly elongated ENE to WSW and that appears to be just SE of the middle. On the northern side the halo of the galaxy is slightly larger but fainter. With AV faint structure is visible and a darker region can be discerned NW of the middle. A faint but beautiful galaxy with details.
To the NW is a mag. 13 star, 1/4 FoV to the ENE is the galaxy NGC3649.

Rated it 7/10.

In 2009 I observed it under Dutch skies in a 12" SCT, but then and there it was no more than a NE-SW elongated patch that made for a tough observation without use of averted vision.

NGC3646-1.jpg NGC3646-2.jpg NGC3646-3.jpg

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