Wednesday, November 11, 2015
NGC 7023 (Caldwell 4) The Iris Nebula
The Iris Nebula is a bright emission nebula in the constellation Cepheus. It has a distinctive blue color. In the telescope field, it is a tiny, bright, blueish dot. The nebula is only 18 arcseconds by 18 arcseconds in angular diameter (as compared to 230 x 230 arcminutes for the ring nebula). These images were captured with the 14 inch, using a focal reducer, so the nebula looked like a bright star in the field. These images are heavily cropped and enlarged, showing some of the bright and dark structures in the nebula. The red and blue fringes are caused by aberrations in the optical system.