Double Star Separation

[Scooot]

I'm a bit perplexed by this. Almach is a double star separated by 9.6". Rigel is a double separated by 9.5". I can split Almach easily, in fact it's one of my favourite doubles. I have never managed to split Rigel and I've read on here its quite difficult. So given they're separated by almost the same distance, why is Rigel so much harder.

Is it that Rigel is so much larger and brighter than its pup? Or am I misunderstanding the stats?

[jason.p]

I eventually managed to split Rigel, and it's smaller companion is much smaller than I expected and can seem to be drowned out by the larger. Polaris also took a few attempts but I eventually got it. Next clear sky I'll be trying Almach and Ras Algethi (If I can find them ). Doubles are becoming my favourite objects.

[Stu]

Doubles are much harder when one component is much brighter than the other. Rigel I have split on many occasions, Sirius I have never managed. The brighter star tends to drown out its companion, and if using a Newt then it can get lost in diffraction spikes or a diffraction ring. On their own, the dim component would be relatively easy to see.

Seeing conditions, altitude of the object, collimation and scope cooling are all very important, as is using just the right amount of magnification, not always the highest.

Stu

[Stu]

Almach and Alberio are both lovely doubles, more equal in brightness so quite easy to split. The components are different colours so they make a wonderful sight in the eyepiece.

Stu

[Scooot]

Doubles are much harder when one component is much brighter than the other. Rigel I have split on many occasions, Sirius I have never managed. The brighter star tends to drown out its companion, and if using a Newt then it can get lost in diffraction spikes or a diffraction ring. On their own, the dim component would be relatively easy to see.

Seeing conditions, altitude of the object, collimation and scope cooling are all very important, as is using just the right amount of magnification, not always the highest.

Stu

Cheers for that. I wondered if it was just that. As you say Almach and Alberio are great, but when I look at them their components seem very separated. It just seemed odd to me that Almach was separated by the same amount as Rigel 9.5",which I couldn't split at all.

[Stu]

Yes, totally down to the brightness of the different components. Rigel and Almach are very similar separations, hadn't really thought about it until you raised it :-). Alberio is quite a bit wider separation which I think is why I prefer Almach of the two.

I have always had a soft spot for Mizar and Alcor. A lovely little system which was the first the I ever looked at through a scope after reading about it in a Patrick Moore book.

Stu

[Scooot]

Yes, totally down to the brightness of the different components. Rigel and Almach are very similar separations, hadn't really thought about it until you raised it :-). Alberio is quite a bit wider separation which I think is why I prefer Almach of the two.

I have always had a soft spot for Mizar and Alcor. A lovely little system which was the first the I ever looked at through a scope after reading about it in a Patrick Moore book.

Stu

Sirius is wider at 9.9"

I think mizar and alcor were the first I'd seen as well. I really liked 61 Cygni when I was looking in the late summer.

[Peter Drew]

Rigel was relatively easy to split with a 90mm Maksutov in Tenerife last week. Good seeing conditions giving good star images are essential for double stars with very unequal magnitudes.

[memoryman]

For Rigel, Sirius or any double star with one much brighter component try using an occulting eyepiece. You can't buy them now, but you can make them from unused high mag EP's. I believe they can also be used to block Saturn so you can spot the moons.

http://www.skyandtelescope.com/observing/celestial-objects-to-watch/the-martian-moons-in-200708/

http://www.eagleseye.me.uk/Resources/OccultingBar.pdf

[John]

I've tried this technique of adding an occulting bar to an orthoscopic eyepiece in the form of a thin bar placed across the field stop as per the S&T article. It did help supress the glare from bright sources in the field of view enabling nearby fainter objects to be seen a bit more easily. It's not a "magic bullet" and care and careful observation is still required but it did help to some extent.

 

 

[memoryman]

John nothing worth doing is ever easy! ?

[John]

48 minutes ago, memoryman said:

John nothing worth doing is ever easy! ?

True. In the end it was aperture, excellent optics and decent conditions that showed me Sirius B rather then the occulting bar to be honest. But it was fun to experiment

 

[chiltonstar]

If you're using a driven EQ mount, you can move the primary star just out of the field of view to simulate the effect of an occulting bar/disk.

For me, splitting difficult doubles like Sirius and Antares depends most critically on "seeing" - getting a night, often hazy, where the image is super-sharp and steady. As John says, you do need decent optics though, and enough aperture to resolve the pair theoretically.

Chris