More Doubles for a Moonlit Spring Night

by Jeff Barbour


Staked out some eighteen doubles (excluding those usually dropped in on) for observation during the lunar second quarter. As it turned out, the April Full Moon came and went before conditions improved enough to complete this venture. Even so, conditions were really no better than they'd been five days earlier. By the time things wrapped up this evening (11:00PDST) - the Moon once again emerged. Meanwhile, rapidly falling temperatures and a late start getting 150mm MCT Argo out meant continuous (but relatively mild) tube currents throughout the evening. The sky was none too supportive either. Rapid changes in air temperature plus thermal currents from a warmish earth meant 6/10 stability. Add to this variable cirrus clouds above and you can understand why I may not have been 100% successful making pairs out of single stars...

Of course, before launching into the evening's program, dropped in on Jupiter at 210x. Actually, and (quite momentary) got a fine 7/10 seeing view: Rifted SEB. NEB Belt-edge irregularities. White oval approaching the CM. Diffuse EB. Well-delineated NTB, and a definite STB. But the Galileans showed walking disks and soon began to flare as the scope sensed a distinct change in temperature with the change in venues. Well, when you get a Mak you also get a lesson in this sort of thing!

Turned Argo on the pearly-white Castor pair. Very distinct - but no sign of airy disks or diffraction rings. Simply much too luminous for sky conditions. Theta Auriga? Obvious but disparate secondary due south that lay safely beyond the flashing tentacles of its brightish primary. Theta, like Castor, will soon be lost to us. Gamma Leonis? Like Castor, widish and easily resolved. Due to dimmer apparent magnitudes however, a better sense of distinction between airy disks and diffraction rings. Like Castor, quite lovely with perhaps a more intriguing set of colors (warm yellow primary, and blue-tinged secondary). The obviously dimmer companion trailed to the south.

Now on to a few studies I'd been attempting from various locales all week with little hope of success. First off:

Name Star RA Dec Comp Mag1 Mag2 Sep PA U2000 Spec Notes

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.

Despite the relative dimness of the primary (magnitude 5.8), only caught glimpses of extinction level (probably imaginary) secondarys at a variety of position angles. Meanwhile, tube currents created an apparent brightening on the first diffraction ring. This could easily have led me to believe I'd seen a disparate playing "ring around the rosy"! So, nothing here. I'll just have to keep coming back until I get that one super-fine night of superb transparency AND stability. Like Iota and Upsilon UMA, this one could prove to be a life-long commitment!

Hw about Kappa Leonis?

BU 105-AB KAPPA LEO 09 24.6 26 11 AB 4.6 10.4 2.4 211 143 K0 Y/B

Surely at magnitude 10.4? Well, again nothing definitive. Possible bluish companion south and slightly trailing. This near the region of what would be a first diffraction ring on a better night. Well, lets see south and slightly trailing is somewhere around PA 143 degrees isn't it? Hmmmm... This one is close. Except that south and trailing is where the brightening on the first diffract tended to be. Could be a case of "wishful thinking". Another night, the same double, methinks. But doable!

Dropped southeast of Rho Leonis for:

STF 1450 49 LEO 10 35.1 08 39 5.8 8.5 2.2 157 190 A0 A is the Algol-type system TX Leo.

Here we find a nicely-joined pearlescent primary with 8th magnitude aqua secondary south and trailing about 2 arcsecs. Looking at the data above, the PA seems a bit awry but this was a definite resolve and not simply a brightening on a diffraction ring. I'll take it!

Now one thing I noticed about Leo that distinguished it from Ursa Majoris was the greater frequency of "pairs of mixed color". Yep, the old Lion has a bit of the peacock about itself while that "earthy bear" never seems to stray too far from your basic population I yellow!

Thence east toward Sigma and:

KUI 54-AB CHI LEO 11 05.1 07 20 AB 4.7 11.0 3.6 268 191 F0

Time to get my "Chi" circulating... Here I find a yellow primary with distinguishable airy disk preceded slightly to the north by an extinction-level "secondary" separated by about 5 arcsecs. Had the PA not progressed to almost south-southwest year 2000, I might almost believe I had resolved this one. Certainly more visits under better conditions should reveal the error of my ways.

Iota Leonis next. This one has plagued me since fellow observer Otto Piechowski first brought it to my attention. Then, on a decent night while snatching views at the Houge Park Public Star Party, got a superb resolve through an AP155 APO. This view should be replicable through Argo (save for a brighter first diffraction ring) but has not yet proven itself out.

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."

Here's a bright yellow primary with flashing virtual image leading a faintish secondary. The secondary lies just outside of where a first diffraction ring should appear. And no, I don't think the listed separation is quite right. Probably closer to 2.0 arcsecs than 1.3. Frankly, there is just too much inaccurate data on the web in regards to binary systems. And of course, I'll be back until I get that consummating view!

Well north of Iota, and within the Lion's haunches lies:

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

Of all pairs observed this evening, 90 proved to be the most mysterious. Both stars showed airy disks. (The secondary's on the limit of solvability.) Primary showed a certain "faint fuzziness" suggestive of a diffuse first diffraction ring. Though obviously of differing magnitudes, the pair is not quite "disparate" - more an unequal matched pair. The 7th mag secondary lay about 3 arcsecs south and slightly leading the primary. Most intriging was way the two stars "swapped" colors. At any point, one appeared bluish while its mate - orangish. Never could pin 'em down. Just noticed the contrast. Shall we call this one Leo's "Blinking Binary"?

Though the "Blinking Binary" took the prize for "most mysterious", the more northerly double:

STF 1555-AB 11 36.3 27 46 AB 6.4 6.8 0.6 143 106/ 107/ 147 A3 A is a sp-bin

proved the most beautiful. This superb pair displays outstanding color contrast (warm yellow and aqua). It also appeared less evenly matched than suggested above. (Probably a consequence of visual bias toward yellow over blue.) Finally the separation proved to be much wider than the .6 arcsecs annotated above. (Easily distinguishable at 210x - although not very distant. Possibly 1.5 arcsecs or so.) Given these discepancies, might normally begin to think I'd found an entirely different pair. However, the secondary was seen to trail to the south - giving a PA of 135 degrees or so. And this maps quite nicely against the 147 degrees documented above. I am content and will probably revisit soon to get a better sense of what magnification "thinline resolves" the pair.

To be accurate, there was a bit of a delay between observing Chi and Iota Leonis. For you see, Backyard Boulder Creek is a bit disadvantaged foliage-wise to south and southeast. So, while awaiting Iota's emergence, revisited a few doubles in Ursa Majoris. And without comparing views to those documented at , I just want to touch on the high points as follows:

Upsilon UMA: Extinction-level secondary leading and to the south. Absolutely no sign of an airy disk on the bright third magnitude primary.

STT 199: Faint companion 5 arcsecs trailing and slightly south of primary. Best view 150x.

Iota UMA: Something I know not what, leading and to south at the limits of a flaring primary spurious stellar image at 210x. No confidence, probably an atmospheric artifact.

Nu UMA: Definite but difficult faint bluish secondary trailing and to south of bright yellow primary.

Xi UMA: Occasional thinline separation at 150x. Confirms 6/10 seeing stability. Resolves cleanly and disticntly under 7/10 seeing at even lower magnifications (120x).

While resolving STT199 didn't have to slew far to locate galaxy NGC2841. Even with the Moon well above the southeastern horizon (and recently post-moonalpausal) could detect a starlike nucleus with definite north-south orientation (at 150x). For me all this is a welcome sign change for soon I hope to "reconfigure" for deepsky mode. BTW: In locating this galaxy, thought I caught a very faint companion some 10 arc minutes west and slightly south. Not on my charts...

And, of course, no evening is complete without a telescopic limiting magnitude check. Found I could just hold the 12.7 magnitude test star in Praesepe at 70x. This through what was probably the average transparency of a sky beset by wafting cirrus clouds. So assuming 6/10 stability. and 11.7 magnitude stars held direct at 70x, dimmest star holdable unaided calculates out to be magnitude 4.8. Yup - I can "just barely" see that...