Interesting object

http://legacysurvey.org//viewer/?ra=191.3811&dec=28.7827&layer=sdss2&zoom=13&ngc

That’s a reflection from a bright star off the edge of the SDSS chips.

I’m not sure why you can see two lines (rather than one).

One line (the lower one) corresponds to an SDSS Field boundary; the other a Bounding Box boundary.