I did a bit more searching for data on 7 Aqr (BU 1034) because I made an attempt on it recently with my newly obtained 140mm ED refractor. The worrying part was that I could see a minute companion in the right PA and I had not expected that with only 140mm. I've not had another good night since then to confirm the observation. What I did notice was that the secondary star did not look as dim as the listed WDS magnitude of 11.4 (primary, 5.7). That gives a delta-m of 5.7.
I went to the Gaia DR2 release and found both stars there. The Gmagnitudes are often somewhat different from V magnitudes, usually slightly brighter, but by differing amounts probably with spectral type having an effect. The magnitudes given in Gaia are 4.9110 and 10.0336. That gives a delta-m of ~5.1, quite a lot less. If we assumed that delta-m and kept the brighter star at 5.7, the secondary becomes 10.8. However, if the secondary is not as late spectral type as the primary (that being K4III - WDS has gK5 not much different), then the visual magnitude could be closer to the Gmagnitude level. That would be a fit for what I saw, if we suppose that the secondary has a visual magnitude somewhere around 10.0 to 10.5.
My observation was made about 10 nights ago so there was no interference from moonlight. Power used was 305x; seen also at 350x and glimpsed at 270x. The observation that John Fitzgerald referred to (mentioned above by me in #3 here) claimed a detection with 4-inch aperture on a night of bright Moon, and the description suggested a double seen elongated with a form that might fit for say a magnitude or two difference in brightness and closer together - 2.1" is well wider than Rayleigh for a 4-inch (1.36"). That observing claim I find not credible.
I will get back to 7 Aquarii if I can before it gets too low in the early evening. Between the clouds, moonlight, and smoke haze from forest fires (severe, and a lot of them, and very smoky) observing lately has been difficult. For those who would like to try this one, J2000 position is 20h 56m 54s and -09 41 51. It's marked on any of the standard atlases with its Flamsteed number (7) in Aquarius.
The observation in #4 above by Mark McCarthy is entirely credible given the aperture and lack of moonlight, despite the recorded difficult conditions. His seeing it with 8-inch mask but not 20-inch full aperture fits the comments by Paul Couteau in his classic book regarding less good seeing conditions - that with unequal pairs the smaller (but still adequate) aperture can sometimes show the double where the larger one won't.
Edited by fred1871, 07 December 2019 - 09:37 PM.