"Go Astro-Fishing" -and you never know what you might catch

A panorama I put together from 3 images (each at ISO6400 and exposed for 30secs) taken with my Canon 600D DSLR with an EOS telephoto lens at f=300mm. all mounted on a polar aligned Star Adventurer equatorial mount.

 This shows an area of the night sky on the border between two Northern Hemisphere Constellations 'Camelopardalis' and 'Perseus'.  At first glance a pretty but unremarkable field of stars. Then I noticed the smudge of  light betraying the presence of my 'old friend and comet C2013 Catalina'. But hang on! what was the separate bit of nebulosity just above and to the right of the comet?

I tried using Astrometry Net to iudentify it, but the search enginne came up blank. I tried my planetarium software,SkyMap Pro9 and it showed no nebulosity in this location. Had  I discovered something new?
No I hadn't!  As a member of Stargazers Lounge, I asked if anyone could advise me and a very knowledgeable member named 'Stu' advised me that the nebulosity was most likely a very faint Mag 16.6 elliptical galaxy PGC168425.
 
I was really amazed that my inexpensive camera and lens combo could in 30 seconds detect and image such a faint and diffuse astronomical object. The apparent brightness of astro objects is defined by a logarithm based magnitude system. The brightest celestial objects such as The Sun. The Moon, Venus Jupiter and the brighter stars like Sirius have negative magnitude numbers.

Apparent Visual Magnitudes

The Andromeda Galaxy (Approx 2.5 million light years distant)    +3.4
Sirius (brightest star)	-1.5
Venus (at brightest)	-4.4
Full Moon	-12.6
The Sun	-26.8

                                                              

 The naked human eye on average can detect stars with an apparent magnitude of +6. Objects with a lower apparent magnitude, for example: the largest asteroid Ceres at Mag +7 would be likely to be unobservable without a visual aid such as binoculars or a telescope. Each increase in positive magnitude, for example from +6 to +7 represents a decrease in brightness of 2.5 times. So any object with an apparent magnitude of 16.6 is very very dim  or more precisely, for an intrinsicly bright galaxy made up of millions of stars, very far far away!

 

As above but annotated to show the comet and the galaxy