Sh2-91 is also known as LBN 147. It is the southeast part of a much larger (about 4 degrees and roughly circular) supernova remnant known as SNR 065.3+05.7. It kind of brings to mind the famous Veil Nebula SNR, but it is comparatively pretty dim and in a very busy star field. It is in the opposite corner of Cygnus from the famous Veil.
Also in this image is Min 1-92 (Minkowski's Footprint), a Post-AGB Star (proto-PN) or pre-planetary nebula. In this image, it is so small, it simply looks like a slightly elongated star. It really needs a much larger image scale.
Because of the different scope / camera / filter configurations I use and my target sequences, the image capture was started with the ATIK camera and finished with my SBIG camera. Hadn't done this before, but it gave me no problems.
Image and details can be accessed at the link below (or by clicking on the Sh2-91 thumbnail image below); full size image can be accessed from the image webpage and has an image scale of 2.53 arcsec/pixel. The annotated image link is provided below, but that can also be accessed from the image webpage.
Scope: FSQ-106N at f/5
Camera: ST8300M (Ha RGB filters) and Atik 383L (Astronomik Gen 2 OIII Filter)
Location: DAA Observatory, Shelter Valley, CA