Comet 21P/Giacobini-Zinner has been discovered in 1900 by Michael Giacobini for the first time. Its another approach has been missed, and in 1913 it was discovered again by Ernst Zinner. Comet solid core has diameter about 2km, and the period is 6.5 years. 2018 year approach is very convenient for northern hemisphere observers, and it may become pretty bright – may reach 6-7mag. On September, 10th comet will reach perihelion. At its maximum brightness comet will be available for binocular observations, but probably will be too dim to glimpse it with naked eye only. Dark sky is very recommended for visual attempts. Over all its 2018 year journey comet 21P will travel across many interesting objects in Cassiopeia, Auriga, Gemini and Monoceros. I have caught the comet on August, 17th in the Cassiopeia, when it was (apparently) close to Heart and Soul nebulae:
I collected subframes to this image under quite good and transparent sky. There were no bright lights nearby, but some clouds were floating across from time to time. I decided to add some hydrogen alpha subframes to the regular LRGB data collected. This way nebulae emissions is better defined.
You can also see and follow the comet position at https://theskylive.com/21p-info page.
Image technical data: Date: August, 17 2018 Location: Odargowo, Poland Telescope: Samyang 135/2 @ f/2.8 Corrector: none Camera: QHY163M, gain 100 Mount: iOptron SmartEQ Pro Guiding: 50mm guidescope + ASI290MM Exposure: LRGBHO 40:40:30:30 x 30 seconds, 15:15 x 120 seconds Conditions: transparency good