Thanks Mike and niharika!
Niharika, the challenge was twofold - shooting in darkening twilight meant the gradients were even more awful than usual. And manually aligning 100 frames - the usual process of automatic comet aligning from registered frames in PixInsight didn't seem to work too well, I think because in many frames there weren't a huge number of stars. Am hoping for darker (and clear) skies to shoot comets Panstarrs and Catalina this week
