This is Cassiopeia A , it's an image from the Wikipedia Internet jpg images , I worked on it to 'solve' and find it's size . I used finally 1582mm F/L and 14 micron sized pixels on the original size image like these , the actual nebula is 6'arc-min x 6'arc-min. . 'Radiation Astronomy/Nebulas-Wikiversity' in GOOGLE Search has content on colors like the Cat;s Eye Nebula with Hubble about how the 630nm band width gets the 'neutral oxygen' ... which sounds like orange color x
