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Splitting Rigel


Space Hopper

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Sirius in a 70mm refractor I would find very unlikely to be honest, the physical separation of the pair is minuscule, they are only 20AU apart in real terms and Sirius A is about 150,000 times brighter than Sirius B. Quite often the angular separation of the pair is stated as being similar to Rigel however the Sirius pair at their most favourable are only an average of 4.6 seconds of arc apart. This varies from about 3.5" to around 7.2" due to the highly elliptical orbit

Whilst the 70mm may be able to separate objects this close, in theory as low as about 2 arc seconds under ideal conditions, I would be surprised if this was achieved for this pair due to the brightness difference between them, perhaps under ideal seeing when the pair were at their greatest separation it may be done as a fluke, but to be honest I have known people struggle in scope much larger than 70mm and fail.

I have not seen it with my 8" SCT, but I have seen it with my old 12" SCT, but seeing conditions here in the UK are pretty ropey..

Rigel is also a triple star, the B component is in fact a very close binary, but don't expect to separate them, they are in a tight orbit and at the estimated 860ly (Hipparchos 2010) distance they are spectroscopic only, even Hubble cannot separate them..

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John

The distance between the pair is quite large at the mo and when Tony and I split it we used moderate magnification.

Cheers

Ian

Hi Ian

what kit were you guys using to get the split? And what magnification? I;ve failed to get a split on sirius in any of my scopes at any magnifcation up to around x250 ish (and higher in my 8"sct - although the conditions were nowhere good enough to support that high). I think Shane is right - as sirius never seems to get that high the seeing conditions have to be just perfect I guess.

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Rigel is a very easy split in my 11" SCT - clear air between them. So the angular separation for Sirius B should not be an issue. I will try this "diffraction" method. I love a challenge like this...... :) As said by others though, Sirius' low altitude in the UK does not help.

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Hi Ian

what kit were you guys using to get the split? And what magnification? I;ve failed to get a split on sirius in any of my scopes at any magnifcation up to around x250 ish (and higher in my 8"sct - although the conditions were nowhere good enough to support that high). I think Shane is right - as sirius never seems to get that high the seeing conditions have to be just perfect I guess.

I believe Ian was using his 10" Orion Optics Maksutov-Cassegrain Mark (Ian will correct me if I'm mistaken !).

I've tried with refractors up to a 6" used with a Chromacor CA / SA corrector (essentially the equivalent of an ED150) but with no success, thus far at any rate.

From Ian's feedback I may have been using too much magnification though and this sort of figures with the experiences I've had with E & F in the Trapezium group where the magnification needs to be just right, ie: not to low and not too high, to spot them with smaller aperture scopes.

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Rigel is a very easy split in my 11" SCT - clear air between them. So the angular separation for Sirius B should not be an issue. I will try this "diffraction" method. I love a challenge like this...... :) As said by others though, Sirius' low altitude in the UK does not help.

I don't think the low altitude is as much of an issue as we may think, Sirius rises high enough for stable air when the atmosphere is clear. Rigel and it's companions (visible component) can be split very easily, I have done it simply with my ETX125PE in the past, the brightness difference between the two components is not that great a difference, after all even Rigel B and C are both B9V stars and Rigel B has a visual magnitude of 6.9, not exactly a difficult object. It is only about 500 times fainter than Rigel itself and with their almost 10" separation they are manageable even in a decent 3" refractor or a small Mak-Cass.

Sirious A is more than 15,000 times brighter than the B component, which is a diminutive white dwarf about the size of Earth, and even at it's close proximity of just over 8.5 light years, it's visual magnitude is not great at 10.02, however when placed so close to Sirius itself, at a maximum separation of 7.2" it is a very challenging object indeed. Remember that Sirius had been studied for about 200 years prior to the discovery of Sirius B in 1844 by Bessell, and they had been using some pretty large scopes, and although their "quality" may not have been as impressive as today's commercial units, their sheer size made up for this

Here is an Image of the pair taken by the HST, demonstrating the difference in apparent brightness ably.

http://upload.wikimedia.org/wikipedia/commons/f/f3/Sirius_A_and_B_Hubble_photo.jpg

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I don't think the low altitude is as much of an issue as we may think, Sirius rises high enough for stable air when the atmosphere is clear. Rigel and it's companions (visible component) can be split very easily, I have done it simply with my ETX125PE in the past, the brightness difference between the two components is not that great a difference, after all even Rigel B and C are both B9V stars and Rigel B has a visual magnitude of 6.9, not exactly a difficult object. It is only about 500 times fainter than Rigel itself and with their almost 10" separation they are manageable even in a decent 3" refractor or a small Mak-Cass.

Sirious A is more than 15,000 times brighter than the B component, which is a diminutive white dwarf about the size of Earth, and even at it's close proximity of just over 8.5 light years, it's visual magnitude is not great at 10.02, however when placed so close to Sirius itself, at a maximum separation of 7.2" it is a very challenging object indeed. Remember that Sirius had been studied for about 200 years prior to the discovery of Sirius B in 1844 by Bessell, and they had been using some pretty large scopes, and although their "quality" may not have been as impressive as today's commercial units, their sheer size made up for this

Here is an Image of the pair taken by the HST, demonstrating the difference in apparent brightness ably.

http://upload.wikime...ubble_photo.jpg

A most thorough analysis. Agreed on all points. I am going to check again after I have my collimation spot on.

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Great info on Sirius, as I thought, it's a pretty serious challenge needing very good conditions and the right kit.

Back to Rigel, I've just been having a look with my trusty ZS66 and it was a fairly easy split using a 3-6 Nagler zoom. It was visible at x77 (5mm), and clear at x97 and x129. Very nice, not tried it in this scope before.

Stu

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Finally had my first glimse of Sirius B. Last night here was interesting - strong winds, a lot of Moon, with clouds flying across from the W, and patches of clear sky. As there was very little star twinkle, I set up my 5" Mak at x190 and waited for the clear patches to look at Sirius. When the seeing was good, it was very good, with a stunning diffraction pattern around Sirius like a spider web minus the spokes. Every now and then, I got a tantalising glimse of Sirius B (the Pup) at about the right PA. Now I know what I'm looking at, I'll continue trying!

Chris

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  • 2 weeks later...

I have just come in having had some good views of Jupiter but the sky was quickly misting over and having read this thread a while ago thought I'd have a quick look at Rigel. Had to spend some time looking at x166 but had hints of the B component, will go back when the skies are clearer for another look.

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It all comes down to seeing. In one good night not only I managed to split Sirius with ease but I even took a photo for Sirius B (the Pup) afocally with my hand-held iphone camera.

Jason

yes, I agree - the seeing has to be very good! Difficult in the UK because we are too close to the North Pole, so Sirius is rather low down. Nice picture of the Pup.

Chris

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So much is conditions. Rigel for me is very easy, even my 70mm ED splits it, so it can only be down to awful English weather. Sirius, now that is a diiferent animal altogether, I looked at it many many times before I got a split, even then I was not sure. The last two monthes doing the work on the Delos reviews I have split it a number of times. Crazy as it sounds even using a 35mm Panoptic on the 190 M/N, I did it two nights running and I was sure I was getiing it. After a couple of glasses of my home stilled brandy my scopes will split anything. I am of course much further South.

Alan.

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I got Rigel tonight for the first time, and I was surprised how easy it was. I'd tried before but with no luck, so was very happy to bag it at last.

As for Sirius, it's much to low for me to split. But I had a great view of it a few weeks ago, really low and flashing different colours through the atmosphere, it was really quite a sight.

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I could comfortably split this last night with a 12mm (100x) ep, but it's a nicer split at 133x and upwards. My scope wasn't that cool at the time and I was getting some bright diffraction spikes so I think I could've got a below 100x mag quite easily.

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  • 2 weeks later...

Sorry to res' a slightly dead thread, but is it possible to split Rigel with fairly basic equipment? I have a Sky-Watcher 150p, 2x Barlow, and the standard 25mm, 10mm EPs.

I've got a clear sky tonight (apparently), and Rigel is right outside my window.

Thanks!

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Rigel is an easy split with my 4 inch refractor so should be a piece of cake for your 150mm newtonian. Albireo is an easy double to split - even 15x70 binoculars will do it, but it's the contrasting colours of the stars that set this one apart.

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