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Some advice needed on observing the Pup


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I had a decent go at Sirius this week and not surprised I came away doubtful given how low in the sky it was. I want to split this one and what I know is that it should be higher up, and that a UHC is going to help cut down the glare. 

My star atlas, Interstellarum, Shows three stars superimposed over the huge disc of Sirius per attached pic. Now I'm not sure how close these really are and if they may mislead me from the real thing!  

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The chart shows the companion to be due East and I can say I certainly didn't see that on the night. In fact the image was dancing around so much it would have been impossible. However I was playing around with the in-focus to observe at 200x and when I had about 8 diffraction rings around the star, I was consistently seeing a smaller disc like object on the outer ring in the direction of North.  That took ages to confirm because of my confusion over the angle of the diagonal, but it was north. It just made me wonder: can you spot the companion in-focus this way or perhaps this was just an atmospheric distortion from poor seeing?  The chart doesn't indicate anything significant due north so I'm thinking it's a hoax!

Also, if anyone has been on the case recently do you know the current arc second of separation?  I think I'll tackle some other tight doubles before taking this on again.  Thanks 

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I've seen the pup star quite often with my 12" dob and with my 130mm refractor.

What I've found is that a magnification of around 250x works best in both scopes and that the eyepiece needs to be one that minimises glare and light scatter. I've found a quality 6mm orthoscopic works best in the 12" dob and a 5mm ortho in the refractor. I have seen it with more complex eyepieces and at slightly lower and higher magnifications but it pops out a little easier with the orthos.

In terms of appearance, the pup is a dim point of light that shines through the halo of light surrounding Sirius A. It comes and goes with the seeing I've found.

The separation between the 2 stars is currently a relatively generous 10 arc seconds but it's the massive brightness difference between the two that provides the challenge of course. The pup star is roughly East of the primary (a little N of that now) and trails the primary if you let it drift across the FoV with no drives on. Here is a good piece from Sky & Telescope on cracking this one:

  http://www.skyandtelescope.com/observing/sirius-b-a-new-pup-in-my-life/

As they say in that piece, if the seeing is unsteady then it's probably not worth trying. Wait for steady seeing and for Sirius to get as far above the horizon as possible.

Antares is another challenging split from the UK, I've only managed that one once.

Edited by John
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Great post John, thanks for the info.

Do you think it is doable with a 4" from decent skies further south? Let's say with 10 or 11 extra degrees of altitude?

Might be able to get my Tak away with me at some point soon....

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Alan Potts splits Sirus with his 110mm refractor (or is it a 105mm ?) from his home in Bulgaria so going south does help. I reckon I've been close with my ED120 and FC-100 DL from here but so far, "no cigar" with those scopes.

I reckon you would be in with a good shout with the Tak at 30-40 degrees N.

 

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The concept has always fascinated me. I found a Google (image)
search on "Sirius Pup" yields some rather unexpected results...
But we return quickly to the more Astronomical association? ;)

Edited by Macavity
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That's great information @John many thanks for providing it. I think as it gets deeper into Winter will be best as it's higher. Just need a crisp, still night. 

My 7mm Nagler with Barlow is 257x; should hopefully do it. Best give the lens a polish first ;) 

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Thanks for the tips John! Didn't realise the Pup was visible with such a small scope. I've never actually tried it myself, but we have two big refractors and a few orthos in Cambridge so I'll definitely try and give it a go this winter.

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Great thread - Seeing the pup for the first time is now on my list for the winter. Hopefully my new scope will arrive in the next month or so which should help a fair bit.

Edited by GavStar
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Given excellent seeing, I don't  think it is too hard.....

I've certainly seen it with both of my Maks and my ED80,  but not my long focus 102mm achro; once you know what to look for, it gets a lot easier. As John says, look for it behind Sirius A as it trails.

Chris

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