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Alnitak

kniclander

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Doc

Doc

Posted
Posted

On paper A is 1.8 and B is 3.7 mag sperated by just 2.6 seconds so in theory a 10" should seperate it.

But remember this is a dob and I don't believe dobs are good at splitting doubles.

Even I struggle with a 16" dob to split this one.

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lunator

lunator

Posted
Posted

Hi Dan

This pair is within the capabilities of your scope. I have achieved a split with my 8" scope.

The challenge is probably due to you having to track the star in the dob.

Do you have an eyepiece that will give you at least x150 magnification but also have a field of view that is wide enough that the star can stay in view for more than a few seconds.

Rgds

Ian

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kniclander

kniclander

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Thanks for the posts everyone. Ian I tend too use an 8mm Burgess optical orthoscopic which gives me 150x exactly and a 60deg FOV.

Talitha, I like the occulting bar idea :D

I think also, I need to wait for Alnitak to be higher in the sky.

Doc, I don't believe (or maybe I don't want to believe) that dobs aren't great for splitting doubles - I don't see why a well collimated dob wouldn't be but I seem to be swimming against the tide a bit here...

clear and cold again tonight :hello2:

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Doc

Doc

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I don't want to believe it as well but I seem to be able to get clearer splits with my refractor then my dob.

It must be a collimation issue but with my laser collimator it looks good.

This collimation issue is a pain in the backside.

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canuck

canuck

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Posted

I'd always heard that the absence of a central obstruction is what makes the refractors better.

If I understand it correctly, the lack of obstruction is what helps increase contrast in a refractor. :D

Thanks for this thread, I had never identified Alnitak as a double star, and usually just stumble upon them accidently...but decided to have a look.

I had two scopes out for comparison this evening, both 4" achromat refractors, 1 x Tal 100R, and the second, a fairly rare 1980's Carton 4" F13. I was surprised to see hints of a double at just over 100x in the Carton, and it was easily split at just over 200x. I got a bit carried away and barlowed my way up to 288x, and while the turbulence made it a bit ridiculous, it was still quite usable magnification. Some great glass comes from Japan, doesn't it? :hello2: The best view came from a 6mm Ortho at 216x.

Interestingly, I couldn't split it all in the Tal.

A little picture of the Carton:

post-13332-133877351129_thumb.jpg

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Lady Isabella

Lady Isabella

Posted
Posted

How hard is it to split Alnitak? Using a 10" dob that I think is quite well collimated and I don't see even the smallest hint of doubleness :? . Has anyone split it and with what?

Dan

Hi Dan

Just got in after observing this star with an 80mm Refractor.

Had a good split at 217x, companion star appeared to be very near or even in the diffraction ring. Also saw the fainter 10th magnitude component of this system.

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  • 2 weeks later...
Starfleet

Starfleet

Posted
Posted

How hard is it to split Alnitak? Using a 10" dob that I think is quite well collimated and I don't see even the smallest hint of doubleness :? . Has anyone split it and with what?

Dan

I could make out the double nature of it with a 10 inch dobsonian, but I wouldn't say I separated them apart! More like a lengthy elongation sorta thing if you see what I mean?

Another thing I like to know is would it appear even more difficult to split on a CCD image or less difficult compared to visually? Intuition tells me close doubles are less resolvable photographically compared to the naked eye...? :wave:

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  • 3 weeks later...
Lady Isabella

Lady Isabella

Posted
Posted

Had another go at this star, this time used a Tak 102mm f/8 scope.

At 41x the double nature of the star was evident with a peanut shape. Split was obtained at 109x, while 320x gave a stunning view of the two stars. The companion star was just touching the outside edge of the first diffraction ring. A beautiful sight.

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lunator

lunator

Posted
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Had a crack at thi slast night in the OMC250.

The was nothing visible at x94 (24mm Hyperion) but at x188 using the pentax XF 12mm the secondary was just visible against the edge of the primary :hello2:

Cheers

Ian

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kniclander

kniclander

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I got the "snowman" effect using my 6" dob at 150x but under very very still skies in serbia far far away from any built up areas. By "snowman" I mean the secondary looked like a little bump on the primary. Not a split, not even a peanut but definitely two stars. Finally. :)

btw the three stars (there is a dim third star a little way away) looked very roughly in a straight line with the primary in the middle. If that's not right then I must have imagined the snowman's head :scratch:

Dan

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lunator

lunator

Posted
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Hi Dan

Here's the info.

5h40m45.50s -01°56'33.0" D* STF 774 Aa,B m: 1.88/ 3.70 1822: 2.3"/152° 2002: 2.6"/166°

5h40m45.50s -01°56'33.0" D* STF 774 Aa,C m: 1.88/ 9.55 1781: 60.0"/ 7° 2003: 57.3"/ 10°

It loks like you saw the B component :) :)

Cheers

Ian

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  • 3 months later...
magnahrl

magnahrl

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Posted

Hi!

With my C80ED at 160X & 208X I don`t have a clear split, but it`s sort of elongation. When seeing is relly good I get a clear split. It`s a bit like Izar.

With my Intes MK66 around 200X it`s very beutiful. Two well sepereted stars, one bright and the other a shy little one, black space between them. In my OO UK 8" f/6 Europa (1/7 PK) I also see two nice stars just touching att 171X& 240X. Nota bene Orion never gets up high in the sky so Iam very happy & proud to have such a clean sep/ elongation. Also seldom the seeing cooporates. I don`t notice any colours.

Izar is easier, `cause it gets higher in the sky but delta Cyg, is harder, though I can observe it at zenith. I guess it`s because the mag differnce is larger in delta Cyg....still I can Elongate/sep in all my 3 scopesicon7.gif

Regards,

Magnus,

Sweden

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Kokatha man

Kokatha man

Posted
Posted

This isn't eyeball but rather imaging.....but I don't seem to have any problem splitting Alnitak: here is a "Darh Horsehead etc" image stack of short exposures with the ED80, clearly separating the A and B stars.....when imaging I think that many people tend to go the "much longer" sub mantra and invariably burn it out.....just as an aside there is a much closer companion to Alnitak A which is the blue supergiant (class O).....Alnitak B being a B-type 4th magnitude star and Alnitak Ab which was "found" in 1998 (O-type also and much closer to A)

Pardon me if this is already in one of the posts above.....I didn't read every one....!:):):(

post-16205-133877368146_thumb.jpg

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