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Splitting Alnitak.


Spaced Cadet
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I tried to give myself a little challenge over the last weekend to see if I could split Alnitak with my Televue 85 and Tal 100RS. The star seemed to shimmer at high magnification in both scopes (they were out long enought to cool) with no sign of the secondary. My books say it requires at least 75mm aperture to split it, so why couldn't I do it with a 100mm aperture?

Is it just the case that the atmosphere over SW England was not stable enough?

Edited by Spaced Cadet
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Hi SC

Altinak is a tought split.

Here is my note on the pair. It took me a magnification of x188.

Cheers

Ian

STF774Aa-B white/blue Tight split. Subtle colour contrast Scope:250mm Magx188 Separation 2.4" Primary 1.9 Secondary 3.7

Edited by lunator
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Last night with my 45 year old 76mm f/16 Dixons (Prinz optics)refractor, I had a very good clear split at 120x.

I have no trouble splitting this pair with my 102mm f/8 scope, you may have been unlucky and had some bad seeing last night.

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I understand that Herschel missed splitting Alnitak so its not easy. The separation is 2.6" between a 1.9 mag and a 3.7 mag star so you might just split it with your 85mm under the very best sky conditions. Generally double stars observers quote good weather, dark adaptation, averted vision and patience. So give it another go you might be successful next time.

Mark

Edited by MarkC
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Talitha

I would think that you will be able to split the pair with your scope.

If C.A. is a problem then why not try an aperture mask, I have seen

several reports of people doing the job with a 70mm Pronto scope.

My 76mm splits it quite easily but it is f/16 and is a wonderful double

star scope. Just be careful if using an 80mm mask as the star may

just appear as a brightening in the diffraction ring.

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Thanks Towa, i've got a WO VR-1 filter if i need it for the CA. It'd be interesting to see what happens if i just remove the center cap on my OTA cap, though. The little opening is about 2".. probably too small? Thanks for the illustration too, it's great to know what to look for.

And thanks for the link, Dan.. i forgot about that thread.

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Hello!

It's mostly clear where I am at the moment and I had another look at Alnitak. Although it is a bit breezy right now, I did see the companion star in moments of calmness. Maybe it was the problem of my lenses misting up last weekend in the lousy weather that prevented me from seeing it!

Thanks everyone!

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I've enjoyed this thread since I spent hours and hours in Photoshop trying to find a way to split the blighter in my deep sky Horse-to-M42 mosaic image. I ended up with a half split.

Please forgive this digression! I will have a crack at it visually when the moon goes. Seeing is the thing, generally much better in the wee hours than the evening here.

Olly

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Hi Space cadet, glad you split it ok, my Tal 100s do it no problem, but you need steady (not transparent) seeing...the very sparkling twinkling nights look pretty but are often useless for splitting test doubles - great for DSOs though!

Another one I sometimes struggle with is Delta Cygni...anyone else have problems with it?

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[quote

Another one I sometimes struggle with is Delta Cygni...anyone else have problems with it?

This is how it appears with my 102mm f/8 refractor at powers from 100x - 200x. In the 4 inch scope it appears to just clear the diffraction ring.

With my 80mm scopes it sits bang in the middle of the diffraction ring. My 76.2mm gives a better split than the 80mm as part of the secondary appears in the inter space between the Airy disk and diffraction ring.

post-17619-133877422082_thumb.jpg

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Hi Space cadet, glad you split it ok, my Tal 100s do it no problem, but you need steady (not transparent) seeing...the very sparkling twinkling nights look pretty but are often useless for splitting test doubles - great for DSOs though!

Another one I sometimes struggle with is Delta Cygni...anyone else have problems with it?

It wasn't really a clean split. For very brief moments, I could see the diffraction ring and passing through it what looked more like a blob joined to Alnitak, which I assumed was the secondary.

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