At the Oregon Star Party a couple weeks ago I finally got my 8 inch f3.3 scope together enough to be functional, and had a blast checking out some well known objects that are too large to enjoy in their entirety with my larger scopes. The most startling and exciting observation with the 8 inch was of M31, which has a strikingly different visual appearance than I expected. The near side (facing M110) seemed quite straight and two dust lanes were seen, and the far side (facing M32) was slightly curved. The unexpected part was that both ends of M31 appeared wider and curved away from the body of M31 in opposite directions, like water coming out of a sprinkler!

I was using a Paracorr 2 with a 25mm ES 100 degree eyepiece (3.22 degree fov) and the Ethos 21mm eyepiece (2.7 degree fov) for the quick sketch below, which was so quick I didn't bother to add any stars. By the way, my pupils still open up more than 7mm so I'm getting the entire light cone using both eyepieces.

M31_8_inchf3_3_OSP2014_negative.jpg M31_8_inchf3_3_OSP2014.jpg

I've never suspected this appearance in other scopes, and until I started to describe what I'd seen to Mel Bartels - who immediately knew what I was talking about - no one in my vicinity had ever seen this either. As you may know from a recent Sky & Tel article, Mel has made a 6 inch f 2.8 and a 10.5 inch f 2.7 and he calls this the M31 Twist. As we know, M31's shape is a flattened disc from our perspective, but with enough aperture and a wide enough fov, the twist becomes its dominant visual feature - fabulous!

Has anyone else seen the twist in M31, and if so what scope and fov did you see it with?