Problems with the Dog

[alan potts]

The last week or so I have been trying to crack the Sirius Pup double allowing the star to get no higher than in the UK which is about 19 degrees above the horizon. I have to say a few of you have done remarkable well in taming this beast as i have read a number of reports of it being split, which is brilliant.

Last night whilst doing a long session on Jupiter i tried the double as it was rising and have to say that from a very dark site with very good conditions I was unable to see the split.

This means war!

Alan.

[michael.h.f.wilkinson]

It is a dog to split. I found the red filter definitely helped by eliminating atmospheric refraction and reducing seeing. Seeing was still not really good, but what I spotted was a dot that did not really flicker within the flickering mess surrounding the main star. That one dot did not fluctuate as much as the speckles surrounding it, and it kept appearing in the exact same spot, unlike the surrounding speckles. I repeatedly switched filters but only in the red band did I spot this effect reliably. I estimated separation and hour angle, and they matched the images on the web (after doing a flip to account for the star diagonal). On purpose, I only looked up the correct position afterwards to avoid wishful thinking.

[YKSE]

The red filter is definitely of great help in this case, I couldn't split the dog before I got the tips from Michael.

[John]

I've managed it once this season with my 12" dob but no filter. It requires pretty steady seeing conditions and even then I was glimpsing "the Pup" though the diffraction skirts around Sirius. Sounds like I might need to expand my filter set a little !

[Moonshane]

I wonder if being a bit further south helps? Has anyone in Manchester or further north managed a split? I got hints the other night and the occasional 'oooh, maybe' at the eyepiece the other night but nothing I'd be happy to 'count'. I am hoping to have more success as it gets higher/further south earlier in the evening so I can view it in daylight/dusk.

[alan potts]

I have had a hint of but that is about all. Not allowing it to count above 19 or so degrees sort of helps me understand what you are all up against, I sure if I let it get to 31 degrees about the horizon it will be much easier, though with that star you never can tell.

It would be nice to see if anyone above Manchester has done it, I never did years back from Hull with a fairly large scope and that is the same sort of latitude. I think a clear southern horizon is a great help as there is so much rising heat from anywhere near a city, I am luck in so much as i mountains to the south of me, but the direction I am looking at the moment is a town, albeit 5 miles away but it could still have an effect.

Alan.

[Moonshane]

I am looking over rooftops all the way south so might try a different spot to see if this has an effect.

[John]

I have to view Sirius in a gap between my neighbours roof top and some large trees. I get about 2 hours max before it dives behind the tree branches !.

The site in Herefordshire where the SGL star party is held has a nice, low, southern horizon as I recall. 

[alan potts]

Well even with the various roofs and trees you all seem to be doing better than me, so hats off to you all. I am not sure what latitude Yong is at over in Sweden but I know he has done it with the aid of a red filter, but us purists deem that as cheating .

Alan

[YKSE]

It's 57 deg latitude here. I had about one hour's south view between the houses.

The seeing was excellent that day.

It feels like that lucky strike has brought me  weeks of rainy or cloudy nights...

[alan potts]

I was only pulling your leg about the red filter, at 57 degrees I think you have done very well to see it at all, I would have thought that was higher than Manchester. How many degrees is it at maximum elevation Yong? There must be a point where it is just impossible.

I just had a look at it 10 minutes ago, it looked like the soup I made earlier bubbling away, I gave up before I started.

Alan.

[Mike73]

I saw this on CN and thought you guys would appreciate it.

http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/6312366/page/0/view/collapsed/sb/5/o/all/fpart/1#Post6312497

Mods I apologise for linking to another forum.

[John]

I saw this on CN and thought you guys would appreciate it.

http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/6312366/page/0/view/collapsed/sb/5/o/all/fpart/1#Post6312497

Mods I apologise for linking to another forum.

Interesting report - thanks for the link 

Those south Florida skies must be good - 72mm aperture and a budget 9mm WA eyepiece for 48x. Makes my 12" dob and 265x seem overkill. 

He is a lot further south than I am though.

The point about the moonlight brightening the background sky is interesting. I guess the trick is to just hit the time when the Sirius A glare is reduced a bit but the much fainter Pup star is still discernible.

This is what the Hubble Space Telescope made of this pair a while back. It's not that far off the drawing made in the above link with the 72mm scope !

[Mike73]

Interesting report - thanks for the link 

Those south Florida skies must be good - 72mm aperture and a budget 9mm WA eyepiece for 48x. Makes my 12" dob and 265x seem overkill. 

He is a lot further south than I am though.

The point about the moonlight brightening the background sky is interesting. I guess the trick is to just hit the time when the Sirius A glare is reduced a bit but the much fainter Pup star is still discernible.

This is what the Hubble Space Telescope made of this pair a while back. It's not that far off the drawing made in the above link with the 72mm scope !

I don't know much about Sirius and the Pup, I've never even looked for it myself but as you know John its not good comparing visual observations to images....even Hubble images!

[alan potts]

Mike,

Thanks for that link. I think the point here and John refered to it is the location, in Florida the star is almost overhead and scintillation will be at a very minimum, even a bad night will not show it like you have it in the UK.

Cracking it with a 72mm scope even for me here is the stuff of dreams, when I get it higher at a reasonable hour I will try it with my 70mm but I am not going to hold my breath. Last night I tried it lowish and it looked like a pot of boiling stew with lights on.

Alan

[chiltonstar]

When conditions were right, the seeing fantastic, and luck my way, my little Orion ED80 did crack it, but only once so far. I think focus is absolutely critical though to get that tiny point of light. I've been practising on Rigel (much easier), and it's surprising how easy it is when the focus is absolutely right, and how difficult if there's the slightest focus error.

Chris

[John]

I tend to use Rigel, E & F Trapezium and Sigma Orionis as sort of "barometers" of how the seeing conditions are in that part of the sky for uneven brightness doubles, prior to having a crack at Sirus. Rigel is also a good test bed as the separation is similar to that of Sirus A & B though the position angle is very different.  

[Moonshane]

re the PA of Sirius B, would you agree that it's about 90 degrees clockwise (in a newt) in comparison with Rigel B? This is what was suggested a while back on here I think by JasonD

[John]

re the PA of Sirius B, would you agree that it's about 90 degrees clockwise (in a newt) in comparison with Rigel B? This is what was suggested a while back on here I think by JasonD

I don't know the actual PA offhand but Rigel B seems to me to appear more or less south of Rigel A wheras Sirius B follows Sirius A as it drifts across the FoV appearing to but just a touch south of due east of the brighter star, all as seen with a newt. So that would be just under 90 degrees in a clockwise direction, yes 

PS: I'd rotated that Hubble image of Sirius and the Pup I posted earlier in this thread to put the pup more or less where I see it with my dob. 

[Moonshane]

nice one John

that rings true with what I have been looking for so I'll keep at it.

[alan potts]

I will do well to see it tonight, thick cloud at the moment. Last night was awful, I was going to have a session on Sirius and that alone, started with Rigel and could bearly split that which I normally find very easy. Ended up watch some old Only Fools and Horses, pure class.

Alan

[entropia]

I looked at Sirius last night.I read (probably in the forum) that it is a double star so I decided to check. I could not see the second star either. Maybe my telescope is too small to see it? (5 inch reflector)

[YKSE]

I looked at Sirius last night.I read (probably in the forum) that it is a double star so I decided to check. I could not see the second star either. Maybe my telescope is too small to see it? (5 inch reflector)

It'll be very challenging with a 5" I suspect.  You'll need really dark sky atoo in addition to good seeing, because you'll need to use 200x or above to split it.

As Alan mentioned, you need to be able to split Rigel easily (in about the same magnification) to have a fair chance to split Sirius.

[chiltonstar]

Rigel is fairly easy, even in a small scope. Sirius is something different, requiring excellent seeing and a good set of clean optics (not necessarily large aperture). The separation is quite large so it is visible on occasion in quite small scopes - some of us have managed it even with 3", so keep trying with your 5" - stick to nights where there is little or no "twinkling" of stars visible.

Chris

[Mark at Beaufort]

I really must have a go at this double. My double star handbook (2006) states a PA of 190 degrees and a separation of 9.0" in 2012.

However, looking at this diagram the PA is less than 90 degrees. On this basis using my 180mm Mak the pup should be on the right of Sirius.