Last night 9 June the seeing around here turned out to be pretty good, maybe a 7 out of 10. Was going to observe some galaxies with the dob but abandoned that and got out the 102 f/11 ED instead. What followed was new territory to me. I'm not exactly a seasoned double star observer and thought, until yesterday, that there was little use other than novelty in extreme overmagnification. So I started out with the 5mm XO on my favourite star, Alpha Sco. The power was 215x, about the upper limit for a decent 4" for general observing. I immediately saw Antares B, a pale turquoise dot ahead of A in the direction of drift. That in itself was surprising. The view showed A's airy disk and diffraction rings, all pretty small and sharp. As in, this could handle more power. Next, the 2.5mm XO, at 435x magnification, from 102mm of aperture. This was now an easy split, and allowed me to see that B was between the first and second diffraction rings, closer to the second than the first. So a fair distance away. I was stunned. I finally settled on the 3.4mm Vixen HR, which at 330x gave the most aesthetic view. Spent about an hour on this object in total, 21:30 to 22:30. Always nice when it cooperates. The telescope appears to be working as intended also. The smallest yet that's allowed me such a straight-forward split.
I never have much success with splitting Antares, as the seeing generally does not normally support more than moderate magnifications here. When I have split it, I have used SCTs rather than refactors.
Nevertheless, U have inspired me to have another ago. I have the same 102mm F11 ED and a TOE 4mm. I will try over the next month and know how it went.
Hi Bob, yes definitely give it a go. I'm in the same boat, coastal location, crappy seeing most nights. I should have compared this side by side vs. the 8" dob but I had put that away too soon so it wasn't cooled and ready.
Antares is an interesting double to split, have done it with my 4" F9 Achro several times but it does need steady seeing, most of the time B is a blue / green smudge nestled in the 1st diffraction ring at 250X. Back when I could use an 4mm ortho, eyes aren't good enough for that short an eye relief anymore. Maybe, next time the seeing is steady I should try the 9mm ortho and the 2.5 Powermate, but with the 5" apo as the 4" achro is now repurposed as my Ha solar scope.
Like you guys, I'm in a coastal location and the seeing is hardly ever better than Pick. 5. Haven't been able to split Sirius this year with the 5" and not from lack of trying, Rigel and Adhara are no problem on good nights though. Is interesting that I have never seen Antares B as a point of light rather than a smudge, quality of the seeing or the optics !!!, that includes with 8" and 10" newts.
At 435x, B did look a bit smudgey to me also. My half-baked theory for this is that with both A and B being point sources, their airy disks are actually the same size (notwithstanding any differences due to their different spectra), so once you're well into magnifying the airy disk (as is the case at extreme powers), it must follow that the disk gets dimmer, with B's being much fainter than A's but a similar angular size. That alone might partly explain some of its appearance. The other thing is its apparent interaction with A's diffraction rings, which could make it appear elongated or otherwise distorted, particularly when B's own diffraction rings interfere.
Last night, I was able to split Antares with my Vixen 140mm with 265x (6mm Tak ortho, barlowed by a shortie 2x).
I has similar success a few evenings back using my Tak 100mm with 245x (same setup).
Prior to that, I failed with my 100mm F11 with 275x. The seeing was not good on that evening and even 180x seemed to be too much magnification.
However, last night was special as the evening had very good seeing. It was an unusual day with Cairns having fog in the morning. That is a rare event here.
So flushed with success, I tried to split Beta Musca, which I have been trying to do for the last 30 years with many different scopes. With 230x, I could see the discs were overlapping, but not separated. At 265x, I could see the discs were close and was not sure if they were separated. With 320x, I had to patiently wait for moments of better seeing and then I could see that they were separated. At 400x, it was too much power and it was never clear enough to see anything.
I am delighted; I never expected to ever see Beta Musca split.
I started to think of more difficult splits, but the clouds rolled in about 8.45pm and ended the evenings viewing.
Last night, I was able to split Antares with my Vixen 140mm with 265x (6mm Tak ortho, barlowed by a shortie 2x).
I has similar success a few evenings back using my Tak 100mm with 245x (same setup).
Prior to that, I failed with my 100mm F11 with 275x. The seeing was not good on that evening and even 180x seemed to be too much magnification.
>snip.
Hi Bob
I dug this one out of the archives, taken back in 2005 with my Vixen ED102S F9 Refractor, Meade LPI Camera, x5 PowerMate and Vixen x2 Barlow, giving me 91800mm at F90!
What a great shot Dennis, and that doesn't even consider its age.
Must try to grab one myself sometime, even though I'm really in the wrong place for double star work.
I have sometimes been able to find the secondary using a green filter, however, in these images, the secondary looks to be blue. I may have to try a blue filter in future.
