Burnham describes NGC 7293 as "..a spherical shell of very tenuous gas, illuminated by a tiny but exceedingly hot central star of 13th magnitude....the estimated diameter (of the central star) is about 2% that of our Sun, but the temperature is over 100,000 degree K." Note the second faint outer shell to the lower left.
There were some guiding issue with this image (mount was okay, just some pilot error).