The hazy season is upon us, and my weather forecast looks like a real mess pretty much every time I check it. Imagine my delight, then, at taking my pup out for a walk a bit before sunset on the Solstice, and seeing rich clear blue overhead!
When darkness finally fell at around 10:00 pm, my tree-free northeastern sky was still clear. I decided to take advantage of the new moon and spend some time sketching M92. As usual, my work is in the sketching forum for any who are interested. I book-ended my observation of that fine globular with the following objects.
First was the curious and very populous system V 772 Herculis (STT 341, 7.2/10.6/10.5/10.3/7.6, 28"/40"/67"/133"), which was recommended recently by Ed (MP173). Here I've listed the five components that are most obvious in the eyepiece, but WDS uses up even more of the alphabet to fully catalog this system. Indeed, my first impression was of a sparse open cluster rather than a multiple star. The three 10th-magnitude components, C through E, make a coarse but attractive group. The G component, wide to the west, is closely matched in magnitude to the yellow primary.
The AB pair itself is a binary with a period of only about 20 years. We're just recently passed periastron, and the separation is changing rapidly. Sometime last year it was less than a hundredth of an arc second, and by the middle of next year it will be nearly 0.3", which is where Otto Struve measured it in 1843. At apastron in around 10 years, the separation will come close to 0.5", resolvable or at least detectable by some of you with larger telescopes. So keep this one on your radar!
Next was STF 2259 (7.3/8.4, 19.6"). I stumbled upon this pair by accident while star hopping from Nu Her toward my next subject. Even in the finder at a magnification of about 20x, this was a cute pair. At 45x in my 150 mm (3.3 mm exit pupil), I saw A as yellow and B as bluish white, while 72x (2.1 mm exit pupil) brought the colors into fine contrast: I wrote coppery and silver blue. Indeed, Simbad lists the primary as a G8 star, on the cooler end of the G spectrum and nearing K land. The secondary is an A1 star, which is on the hotter side of A-type stars. I'm never afraid to report what I see, even when what I see isn't supported by the published data. Color perception is highly subjective, after all. But it's always nice to find spectral types that match my perceived colors so nicely!
The following object was another short period binary, and something of a foolish attempt: 99 Herculis (5.1/9, 1.48"). I'm actually not confident that detecting B is possible for 150 mm of aperture. It was discovered near its widest separation by none other than Alvin Clark, using the 8.25-inch refractor he had made for none other than the Reverend Dawes; so I know it won't take a whole lot more aperture than what I have. If indeed it is possible for me, it will require a perfect night. This night was not perfect, however, and at no magnification was B visible. However, this pair is steadily widening, and although it won't get wider than about 1.6", that small increase might be just enough to push it over the edge during the next several years. If you've managed to resolve this pair, please share your observations! I'm curious to know if anyone has seen B with less than 8 inches of aperture.
Having failed a challenge, I needed some stellar balm for the soul. STF 2351 (7.6/7.6, 5.1") in Lyra, another pair recommended by Ed, was just the remedy. And what a morsel it is! At 45x the components were nearly equal, though I felt that the northwestern star was slightly brighter. 72x confirmed my suspicions, and I noted the PA as south/southwest. The colors were extremely closely matched, both whitish. Surrounding the pair was an attractive isosceles triangle of stars, slightly displaced to the west relative to the central pair. A very pretty object, indeed.
I continued east into Vulpecula to end with STF 2525 (8.2/8.4, 2.2"). Even at 45x, I could easily estimate the PA along the east/west axis. At 72x the pair was deeply notched and occasionally split by a hair, the eastern star now clearly brighter. 90x (1.7 mm exit pupil) split the pair perfectly clean. A and B were both very light yellow, while a third component wide to the north west (HD 338346) had a slight bluish hue by comparison. This is a tiny jewel, and one that I can most highly recommend.
That's all for now! Comments, corrections, admonishments, praises, and reminiscences from your own observations are most welcome.
Edited by nerich, 22 June 2020 - 04:42 PM.