When one has been struggling with cursed objects (DSOs that, despite repeated best efforts, never seem to yield decent data), I have found that it is a good idea to go back to something reasonably basic but still interesting. Messier 17 is just such an object: big, bright, easily identified, and colourful. M 17 goes by several names. The one I grew up with was the Swan Nebula, but it is also known as the Omega Nebula, the Checkmark Nebula, and the Horseshoe Nebula. Most of these names are based on the lighter central region that is seen through most telescopes. If you squint, you can imagine a pale swan gliding leftwards through the middle of the nebula. The distinctive, dark shape that helps form the ‘neck’ of the swan is the result of large clouds of dust blocking the light from emission nebula behind it. M 17 is an HII region in Sagittarius, and resides about 5500 light years from us. Its center is illuminated by one of the youngest cluster of stars; just a million years old.


Date: 13 July 2020
Constellation: Sagittarius
R.A.: 18h 20m 57s
Dec.: -16° 10' 40"
Photo stuff: 18 subs@300s ea.; ISO 800; Canon 60Da on Meade RCX400 16” f/8 with a .7 focal reducer