Located at the base of the east wing of Cygnus, the Swan, 52 Cygni marks the location of the southern segment of the Veil Nebula, which is also known as NGC 6960. I suspect most people who have looked at it have focused all their attention on that long thin strand of nebulosity that extends on both sides of it without realizing that it’s a double. That was certainly my experience until I found it listed in Sissy Haas’s Double Stars for Small Telescopes.
The last time I looked at this beautiful double was in the middle of July. At the time, I had intentions of writing something up on it, but I wanted to get one more look at it first. Little did I suspect that the cloud and fog gremlins were about to join forces and put me out of business for almost a month. But the morning of August 13th dawned bright and clear, and with it came a balmy temperature of ninety-five degrees – which was intense enough to burn the leaves on many plants, like my rhododendrons, to a brown crisp. On the other hand, it was clear when the sun went down, and unlike the evenings of the past month, it stayed that way. At 10 PM it was still a very warm eighty-four degrees, though, which is a bit brutal in a coastal town that hasn’t seen eighty degrees in the daytime – much less at night – since early June. When I gave up about 3 AM the temperature had crawled all the way down to a mere seventy-eight. I went to bed with a window open and a fan pulling air through the bedroom – and woke up at 4 AM freezing to death. Outside, the sky was clouded over, fog was rolling up the street from the ocean, and the temperature had plummeted to fifty-four degrees! End of clear skies for how long??????
What does this have to with 52 Cygni? Clear and warm as it was, that hot air was already being disturbed by the cool air lurking off the coast, causing horrible seeing. Most stars boiled and shimmered so badly that focus was impossible beyond 50x, so looking at doubles was pretty much hopeless. Jupiter had a glow around it, which was a clue that there was some moisture up there somewhere, even though the air felt like sand paper. However, the transparency was still pretty darn good, so I began looking at deep sky objects. At the top of the list was the Veil Nebula, and I figured I might as well see if I could split 52 Cygni. Fortunately, it was high overhead, which gave me a decent chance.
52 Cygni (Σ 2726) (H II 25) HIP: 102453 SAO: 70467
RA: 20h 45.6m Dec: +30° 43′
Magnitudes: 4.2, 8.7
Position Angle: 70° (WDS 2006)
Distance: 206 Light Years
Stellar Classification: G9
The 6.4″ separation of the two stars would lead you to believe this is an easy split, but the 4.5 magnitude difference between them makes it a bit tougher than that. I was using a 20mm eyepiece in my six inch refractor, which gave me a magnification of 76x. As I got my first look of the night at 52 Cygni, I could see the nebulosity flowing from both sides of it. I needed a bit wider field of view to take it all in, though, so I switched to a 30mm eyepiece, resulting in a magnification of 51x. The view of those long, thin filaments of nebulosity was just stunning – and without the use of an OIII filter even! For a moment I forgot that it was the double I was looking for!
Now this is one of those stars that will tease you. The first time I looked at it, I looked and looked and could not see the faint companion. And then suddenly after staring at it for about ten minutes, I realized I was looking right at it! It’s a very small pin point of light nestled up very closely against the much brighter primary. The best way to describe the effect is to compare it to the view of Polaris in a 60mm scope, the faint companion of which can easily be seen with good 60mm optics on a night of steady seeing and average transparency – but, you have to look very closely in order to see it because there is a full seven magnitudes of difference between the two stars. And, as with 52 Cygni, you’ll often find you’re looking right at it without really seeing it until some quirk in the brain quits quirking and allows you to recognize it.
At 51x, I could just detect the secondary’s 8.7 magnitudes of faint light, and yet it was cleanly separated from the primary. Switching back to the 20mm, in moments of steady seeing it was very easy to detect. On this particular night, the primary was clearly a dark orange-yellow, which is the first time I’ve seen that tint. I don’t know if it was the atmosphere or the scope.
Here are my notes from the other side of the cloud-fog-gremlin divide:
July 15th: In a 102mm f/15 refractor, the secondary is a very small pin point of light at 94x; primary has a red tinge to it. Also clearly seen and split in a five inch f/9.3 refractor at 74x. In a 60mm f/15 at 50x, the secondary could not be seen. Averted vision brought it out at 100x, but 150x and 225x made it more obvious – although it was still tough even at those magnifications.
On the west wing of Cygnus is another tough customer, Delta Cygni, which is actually much tougher than this one — you can read about it here — and keep reading into the comments because that’s where the real saga of that devious double takes place.
At any rate, on both wings of Cygnus what you’ll find are built-in challenges just waiting for you to sharpen your observing skills! Don’t wait — clear skies in these parts don’t last long!