15 Bootis problem

The zoomed out Stellarium image is below Aubrey. So if we measure anti-clockwise from the north position, we can estimate an angle of about 110° on the enlarged image. Drat, looks like the experts were right after all...

Hi Aubrey.

I tried to resolve 15 Boo last night, but without success.

I checked several other reasonably challenging doubles in the same vicinity (all in Bootes), as shown below - all observations with a 280mm SCT, using an 8mm Hyperion eyepiece, giving a magnification of 350x, from a suburban Dublin location. The seeing was only moderate to begin with, and the scope took a while to cool down, but it improved as time went on.

ID: WDS14138+1200; RA Dec: 141349+1159
Name: STT279 AB; Mag1: 6.8; Mag2: 9.1; Sep: 2.2"
Observations: Deep golden primary, with a much fainter and paler secondary. They are clearly split at 350X. This was a good test to start with because of the substantial magnitude difference, but with a separation of 2.2", it was resolved without difficulty.

ID: WDS14203+0835; RA Dec: 142021+0834
Name: STT281 AB; Mag1: 7.7; Mag2: 9.7; Sep: 1.5"
Observations: Not entirely convinced that it was resolved at 350x. The primary is golden, and just occasionally there seemed to be a glimpse of a much fainter secondary at approx. the correct position, but the seeing was not steady enough to be sure. A tougher test, and at the limits of what the seeing would allow.

ID: WDS13407+1957; RA Dec: 134040+1957
Name: 1 Boo AB; Mag1: 5.8; Mag2: 9.6; Sep: 4.5"
Observations: Bright, white star, well separated from a much fainter companion at 350x. There is another bright white star in the field, the super wide D component, as well as the much fainter C component which lies between A and D. Easy, despite the large magnitude difference.

ID: WDS14101+2636; RA Dec: 141008+2635
Name: STF1808 AB; Mag1: 8.8; Mag2: 9.6; Sep: 2.6"
Observations: Mildly unequal yellow stars, nicely separated at 350x, but too faint to be really nice.

ID: WDS14116+2802; RA Dec: 141134+2802
Name: STF1810 AB; Mag1: 9.0; Mag2: 9.6; Sep: 2.4"
Observations: A pair of dim golden yellow stars, similar in brightness, cleanly separated at 350x.

ID: WDS14463+0939; RA Dec: 144616+0938
Name: STF1879 AB; Mag1: 7.8; Mag2: 8.4; Sep: 1.8"
Observations: Similar yellow stars, attractively close at 350x.

ID: WDS14484+2422; RA Dec: 144823+2422
Name: STF1884 AB; Mag1: 6.6; Mag2: 7.5; Sep: 2"
Observations: Nice pair of pale yellow stars, both bright, though they are somewhat unequal. They are cleanly split, but attractively close at 350x.

ID: WDS14534+1542; RA Dec: 145323+1542
Name: STT288 AB; Mag1: 6.9; Mag2: 7.6; Sep: 1"
Observations: Similar pale yellow stars, just resolved at 350x, with a clear gap between them. Very nice. By this time the seeing had improved and this close double was cleanly resolved. Note, however, the relatively small brightness difference between the components.

ID: WDS14148+1006; RA Dec: 141451+1006
Name: 15 Boo AB; Mag1: 5.4; Mag2: 8.4; Sep: 1"
Observations: The main attraction and I stared and stared, waiting for moments of steady seeing, but it was not resolved. I returned three times in the course of the session, but still no luck.


As regards the extent to which the magnitude difference affects the difficulty of resolving doubles, I'm sure you're familiar with Lord's index ( fisherka.csolutionshosting.net/astronote...l/LordSplitCalc.html and fisherka.csolutionshosting.net/astronote...Unequalbinaries.html ). My experience ties in very well with its predictions. It's a rule-of-thumb, not a physical law, but looking back over my records I have never been able to resolve a double with a separation of 1" or less when the magnitude difference exceeded 2. That's a little worse than Lord's formula predicts, but my visual acuity may not be so good, and perhaps the optics of the SCT are a little below par?

I agree with you that it would be great if some other observers took up the challenge and reported their observations of 15 Bootis.

Cheers,
Mike

Thank you, Finbarr, for that. Yes it seems we are back to square one.
I can only repeat my strong exhortation that we all get our telescopes and observe 15 Bootis. I don't care what scopes our observers will use; but any refractor achromatic or apochromatics and SCT's I believe will show 15 Bootis B in the 10 o'clock position. Reflectors ought to show B in the 8 o'clock position. We should use magnifications of at least 200X.

My apochromatic refractor is now set up in my back yard.

Happy double star hunting,

Aubrey.

Hi all. Sky conditions were appalling on Wednesday night; and although I did try to split 15 Bootis at 225X, it was a complete waste of time. There simply was far too much high cloud about. The double star was utterly blurred.

I did see an Iridium flare north of Jupiter at about 11.15 pm. It did seem brighter than the -6.7 magnitude that www.heavens-above.com suggested. It was huge! And I did the ISS a few minutes earlier also.

Aubrey.

Good evening, all. I am wondering has anyone managed to observe 15 Bootis in the last couple of weeks?

I know Mike Casey tried valiantly to try split it with 280 mm SCT. But it would not split for him. However, I have split it no less than 5 times during this recent period.

I have just stated on www.cloudynights.com that I am in the tiny minority of being the only one to have seen the secondary in the 10 o'clock position. (My north is up and my east is to the right using a mirror diagonal on my 158 mm refractor.) I would suggest that large aperture telescopes should only be used to separate 15 Bootis. Its separation is only 1 arc second. And yet I can see the secondary star at 225X in a 5 mm Nagler eyepiece. The position angle is currently 108 degrees as described on stelledoppie.goaction.it . But I have sincerely judged it that my reading of 10 o'clock would be something like 280 degrees in PA.
However, two observers on www.cloudynights.com say they have seen the secondary in the 4 o'clock position.

Clear skies.

Aubrey.

I've not succeeded in splitting 15 Boo with my 8" SCT Aubrey, I think a 1 arc-sec separation is beyond my limit unless maybe on a night of perfect seeing.

I have successfully checked out some of your other Bootes suggestions, and of course Izar is a glorious sight.

Also been enjoying your debate with the knowledgable folk over on cloudynights, keep persevering and you'll get to the bottom of it.

Finbarr.