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Hi Goober,
Nice report mate.
Sirius is a very, very tough split in any telescope no matter how large. If it was easy, it would have been detected a loooooonng time before Alvan Clark found it in 1862. The big problem is the brightness difference which is about 9-10 magnitudes. I've seen it split twice I think in 36 years of observing and have tried dozens, if not 100s of times so don't be surprised at all if you fail. The last time I succeeded was a couple of years ago with my excellent 31cm f/5.3 newtonian (Suchting mirror) on a Samson GEM at x410 (8mm TV Plossl + Ultima barlow) in seeing I would describe as excellent -- 8-9/10 on the US scale.
At the moment the "pup" is virtually due E of Sirius in about PA 90, so using an un-driven dob it should follow Sirius across the field. The seperation is about 8 arc-seconds at the moment (almost as good as it gets) and won't increase much in the next several years.
To get a feel for how 8 arc-seconds seperation should look at the magnification you intend to use on Sirius, take a look at the pair in the centre of nearby M47 -- Struve 1121 which is about 8 arc-seconds (almost identical) so you get a feel for it.
Star image asthetics are of little importance -- pump it up as far as you can reasonably go in the conditions. Dust-free squeaky-clean optics are also a considerable advantage because they cut down on the scattering of Sirius powerful glare.
I've seen a great many of what appear (to me) to be "doubtful" reports on the net of seeing Sirius split using 4 to 6" 'scopes at comparatively low magnifications ~ in the order of x100 to x200 where the observer noted that it was "easy to see" -- or words to that effect. Though the observers I feel in the vast majority were "honest" I also think many report a "false positive" as a result of an internal reflection within the eyepiece of Sirius itself.
This seems to me to be particularly prevalent with the multi-element exotic eyepiece designs of today which are more prone to internal reflections (on exceptionally bright stellar objects) than say a quality old-fashioned orthoscopic or plossl. The Kellner is another (old) design well-known for internal reflections. If the pup wanders in PA and/or seperation as you move Sirius around in the field it is an internal reflection. I can remember several times when I thought I had it (and let out an exclaimation) and then moved the 'scope only to see the pup wander. An eyepiece with an occulting bar fitted at the field-stop is also a good though old-fashioned idea (you hide Sirius behind the bar).
I'm not trying to discourage people from having a go, give it a shot by all means but don't expect success so easily! It may indeed take months or years and I'd expect the absolute minimum (high-quality) aperture for success to be in the order of 20cm.
Best,
Les D
Contributing Editor
AS&T
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