by Jeff Barbour
Expected no sky this evening at all. Around 6pm, the possibility of an evening "sucker hole" chase emerged. By 7:00, the sky completely cleared and I started "mission planning" in earnest.
First step was to beat the tube currents by setting up 150mm MCT Argo soon as the Sun dropped below the mountains. Then one hour later, sweep the sky for "The Veiled Beauty" using the finderscope.
Then on to The Royal Monarch and Ringed Wonder as the sky darkened further. Once Polaris was visible, move on to follow the emergence of Polaris-B. Then break to double star observing as soon as the companion can be held direct. The goal? To sift through all those unresolved disparates left over from moontide. Upsilon, Iota, and 51 UMA. Kappa, Chi, 39 and 90 Leo - plus a few of them numbered pairs: STF199, HO377, BU919 - all in Ursa Majoris. Everything seemed to be going my way - except stability.
By 8:00pm, picked up Venus by sweeping the sky with the finder. With Argo pointing the way, was quickly able to detect the planet unaided. Venus showed maybe a 70 percent gibbous disk along with a brilliantly illumined leading edge and CM transition to a softer pearlescent glow. With Venus positioned some 30 degrees above the horizon, not quite able to get clean edge focus. As at Monte Bello last week, no atmo-chromaticism detected. Did notice a thin diffraction spike impaling the planet. But soon realized I was peering past Ajax's (canine member of the household) runline. One thing nice about Refractors, Maks and SCT's - no spider vanes. Very nice feature when viewing intensely brilliant studies. Oh yes, at 210x Venus appeared about the size of the Moon unaided - which in turn is about as large as the Red Planet gets during a close opposition. This is not the kind of image scale I prefer!
Speaking of Mars - due to The Incredible Shinking Planet's "shrunken" state, made no effort to track it down this evening.
Not speaking of Mercury - no effort here either.
Speaking of apparent size - anybody notice that Jupiter is losingmuch of its former grandeur? In fact, the planet at 210x is now about the size seen at 180x during opposition. And "smallish" 180x views of Jupiter were why I bought a barlow lens in the first place! Again image scale. I like it. Sure Jupiter looks nice and crisp at 150x. But have you ever viewed the planet at 540x? It's about the size of a quarter held at a distance that just allows you to read the print. Incredible image scale - but rarely feasible through Argo. And the kind of magnification most experienced observers would think laughable...
Can you see significant detail on Jupiter at 540x? Sure, in fact such a magnification may be used for the same reason that 200x is while viewing bright galaxies - to dissolve low surface brightness detail and make discrete details more evident to the eye. On Jupiter this works too - but generally only while observing the NEB. This night however, under marginal stability, made no effort to achieve "image scale" of this magnitude. For Backyard Boulder Creek still has "Spring Fever": 6/10 stability at best, 7/10 early and just before the local "heat engine" kicked in...
And with Jupe still well within the skies middle-third, immediately caught an ingressing GRS. Stability good enough to reveal the EB (faintly), NEB belt edge irregularities, a condensed NTB, and both frontiers of the STB. In addition, the NPR showed various albedo shadings, and a single white oval could be just seen egressing twoard the leading edge of the planet on the NEB. Decent but not a "knock your wool-socks off" view.
Didn't really spend much time on Saturn. It's a shame what low sky position has done to such a finely-hewn planet. Cassini and SEB, though detectable, were both vague. Posterior ring shadowing lacked any sense of "dimensionality". Probably time to let the Ringed Wonder slip into the Sun's glare. But nah, there does remain the hope and the possibility of one more well-chiseled view before the parting of the ways. And of course, after that you can always hope for one more...
It was time to follow the emergence of Polaris-B. Now before you all laugh at me, let me remind you how difficult it can be to orient an equatorially mounted scope on the Pole Star. Then also let me mention that, during dusk, it is very difficult to tell one star from another through the finderscope - especially one that lacks a perfectly flat field. Having said all this, you must know what happened... I slewed the scope north, centered on a "bright" star, and sat there admiring the fact that occasionally "Polaris" would actually sport a first diffraction ring! Why the seeing must be better than I thought! Half an hour later, and with only the vain imaginings of an "extinction-level" Polaris B behind me,gave up and reflex-sighted Argo on the real Pole Star! And even at 210x, under marginal seeing, there was the companion. So too late to accomplish what I had hoped to.
Thus my plans for the evening were mostly blown. For you see, I'd hoped to record the time at which Polaris-B could be first held under various magnifications. The idea being that difficult disparate pairs have a narrow range of solvable magnifications. Such a magnification appears to be a function of primary brightness, pair separation, and magnitudinal delta. Along with the darkness of the sky and presence of intervening thin clouds.
Let me illustrate: Say you want to resolve Sirius B. Well, we all know that Sirius A is tremendously brilliant and usually overwhelms its dim 8th magnitude dwarf companion. But since the secondary is some 8 arcsecs or so distant, there must be some strategy to improve your chances!
Obviously, you want the stillest possible sky. Then, surprisingly (in Sirius case) you may want a relatively "bright" sky. Why? Because a bright sky (or thin clouds) helps "suppress" the flare and light play of the primary and gives the eye a better chance of discriminating the more pointillistic light of the secondary.
Of course, another variable is aperture. But how much is enough? Any scope can resolve an 8 arcsec pair, right? But what is needed is a scope that can somehow reveal 8th magnitude stars through a dusky sky. One that is typically just dark enough to find Sirius unaided. But most scopes aren't able to do this. You've effectively got minus 1 magnitude sky transparency. You need to go some 9 magnitudes deeper with your scope. For this, quality aperture is a must, along with a well selected magnification.
In observing numerous disparate pairs, I've found that too much magnification diffuses the secondary and makes detection difficult. Too little magnification fails to darken the sky enough to reveal stars of that magnitude. Thus the quandary, and why I was willing to sit there at the eyepiece not-following Polaris-B's emergence at a variety of magnifications.
And what a fine study our Pole Star is in this regard. Most scopes will reveal the faint secondary at large exit pupils. This as soon as you can find it in the night sky unaided. But try finding it under high magnification under the same conditions - especially through an unstable atmosphere! So tough, on-the-edge disparates, are magnification-dependent.
As a result the rest of my evening was pretty much a wash out. There was no base-line of magnifications over time to make reference to. But dutifully, I turned up each unresolved double from the original Spring list. Almost everyone of which showed something I know not what at various position angles which often failed to map against published data. Meanwhile, I could also easily delude myself into thinking I saw "faint blue" secondaries even at varying separations and position angles for a single star!
But to be complete, here's the "skinny" on the various "on the edge" pairs observed:
Name Star RA Dec Comp Mag1 Mag2 Sep PA U2000 Spec Notes
URSA MINOR:
KU 1-AB 16 43.0 77 30 AB 6.1 9.4 2.7 184 11 F2 ALSO HU 917
Faint secondary trailing to north, separated by about 5 arcsecs. Difficult at 210x. More definite at 120. This one should be solvable and only needs higher sky position to confirmed.
URSA MAJOR:
STT 521 UPSILON UMA 09 51.1 59 03 3.9 11.5 11.3 295 45 F0 A is a Delta Scuti-type var.
Something very faint and to the south. This PA does not match published data. This one should also be solvable but it will take a very special night!
HJ 2477-AB IOTA UMA 08 59.3 48 02 AB 3.9 9.5 4.5 24 70 A5 AXBC: Orbit calc\'d. A is a Delta Scuti var and sp-bin.
Occasional 120x glimpses of something faint trailing and slightly north, distance about 5 arcsecs. PA matches but needs confirmation. This is the one I hope to focus on over the next few weeks. Clean resolve or bust! To resolve unambiguously would roll back Argo's "threshold of detection".
STT 199-AB 09 20.7 51 15 AB 6.1 10.2 5.7 133 44 F2
A no confidence illusory "companion". This one about 8 arcsecs trailing slightly south. Due to non-use of setting circles, not sure if I've even located this pair yet.
HO 377-AB 51 UMA 11 04.6 38 14 AB 6.1 12.6 8.2 250 73/ 106 A2
Secondary much too faint under the circumstances. But I could see it if I really wanted too!
BU 919 11 59.3 33 09 6.0 12.0 4.5 16 107 K0
Another "phantom secomdary". This time due south at about the right distance. Due to separation - about as likely as HO 377 above...
LEO
STT 523 39 LEO 10 17.3 23 06 5.8 11.4 7.6 299 144 F5 Mt. Wilson spectral types are F1s and dM1.
Another phantom. Trailing and slightly south. PA matches but not able to "hold" anything - despite extreme aversion. This pair would constitute a breakthrough as well.
BU 105-AB KAPPA LEO 09 24.6 26 11 AB 4.6 10.4 2.4 211 143 K0 Y/B
If anything, leading slightly south at 180x. At one-hundreth the primary's brightness, 2.4 arcsecs is probably well beyond Argo's capabilities. This one probably needs a large "research-grade" scope from a fine observing site.
KUI 54-AB CHI LEO 11 05.1 07 20 AB 4.7 11.0 3.6 268 191 F0
Nearby foliage prevented me from observing this very difficult, but potentially solvable disparate. Like Iota UMA, I'll stay after this one! Like many of the others in this report would establish a new "line drawn in the sky".
STF 1536 IOTA LEO 11 23.9 10 32 4.1 7.3 1.3 141 191 F5 "P = 192 yr., a = 1.92'', motion retrograde."
Conditions did not support resolution of this pair at magnifications used this evening (70, 120, & 180x). A clean resolve indicates excellent seeing. Stars of this type are valuable for assessing seeing conditions. (Very much springtime's Delta Cygni.)
STF 1552-AB 90 LEO 11 34.7 16 47 AB 6.1 7.4 3.4 208 147/ 192 B3 B is a sp-bin. W/B
Elongated with secondary trailing to south at 180x. Definitely tighter than the 3.4 arc secs sighted above. Also on my "short list" for continued monitoring. There is such a variance in observed separation that it warrants micrometric measurement! Or is there another double in this region?
Meanwhile as I fruitlessly tracked down one double after another, a perfect deepsky opportunity passed overhead. Stars visible down to nearly magnitude 5.5. This sky was meant for galaxies - the Galaxies of Spring. How could I possibly ignore them? Perhaps because I will never resolve those "on the edge disparates" during a lunation. They need dark and steady skies. And so do I...