Sirius A and B

[John]

It's turned out a decent night despite some cloud cover earlier.

Now the 12" dob has cooled I've been able to get some tight views of Sirus A with the flare around it well controlled enough to pick out Sirus B (AKA "The Pup") trailing along in it's wake as The Dog Star drifts across the field of view. 

I've been particularly pleased that the Nagler 3-6mm zoom has shown this pairing quite well - very impressive for a 5 element zoom and tonight it's equaled the Baader GO 6mm which is usually the best of my high power eyepieces for splitting Sirius. 

A 6mm eyepiece gives 265x with my dob. I've been glimpsing the B star at 5mm and 7mm as well but 6mm seems to be the "Goldilocks" power with this scope for this target.

I'll be taking in some other targets too, when Sirius goes behind the chestnut trees across the road. Assuming the clouds co-operate, that is.

[Laurie61]

I had a try at Sirius a few nights ago, with the 300 mm, but the seeing was not cooperating. The Nagler zoom sounds like a nice piece of kit  the 5 element design should help with light throughput and contrast.          

[HumptyMoo]

I took a look at Sirius the other night, I am plagued by bad seeing, security lighting and sodium lamps not to mention the weather in general. I post this though because I can only see Sirius as a flared star. Well, to be a bit more accurate, it is a point of light in my 25mm "come with the scope" plossy, but, in my 13mm tv nag it is flared, as are other stars I try and focus on with magnitude 3-4ish and above (less?), Betelgeuse for instance?(very approx...I'm new).

I'm wondering if the nag is highlighting a collimation issue or my seeing is just too bad for this EP. I look through a collimation cap and everything is exactly as described in astro babys page with regards to "in collimation" except for a very very slight bias from the centre dot, to the inside left of the primary doughnut. My Cheshire combo says the 2 are exact, or, if I move my eye slightly, not...

Long and the short of it is, I am waiting for good sky's...Not even sure what my question is here

[John]

Sirius is not a good target to test your collimation really - it's the brightest star in the sky so it's hard to get a crisp image at the best of times.

When I'm checking my collimation under the stars I usually use Polaris because it stays more or less still and it's a reasonable brightness without being too glaring.

With Sirius, apart from good collimation and steady seeing, I've found that eyepieces which deliver a decently high magnification and control light scatter / flare around bright objects are the best to enable the B star to be seen. Orthoscopics seem well suited to the task.

[HumptyMoo]

I wasn't trying to test collimation on Sirius, I was just perturbed as to why it would appear flared under 96x mag, given that the 25mm standard shows it pretty sharp. I know that there is night and day between the 2 EP's so I was never in a comparison situation.

Collimation for all intents and purposes seem to indicate "in line enough to be negligible" so I naturally wondered if it was the EP highlighting short comings or just plain bad seeing coupled to relatively low on the horizon. Or of course my eyes are in need of a good seeing...

In very good conditions what would you say is the rough max magnification I could view Sirius and perhaps Betelgeuse with, to a relatively sharp image? Maybe Betelgeuse is different being very much from the redder end of the spectrum?

Either way, thanks for taking time to reply

[John]

Either way, thanks for taking time to reply

No problem - sorry if I got the "wrong end of the stick" from your earlier post.

I've not managed to see Sirius B with any scope other than my 12" dob although I know folks have managed it with smaller apertures than that and probably less magnification than I'm using.

When I had the scope you have I found it pretty good at splitting double stars. I found I could use 200x - 250x for this purpose if the seeing conditions were decently good. 

Your 13mm Nagler with the 2.5x Powermate gives you 230x which should be in the right ball park. The question is whether the amount of glass involved with that combination, excellent glass though it is, will produce tightly defined image of Sirius and allow the faint glimmer of the B star to be seen.

I think you are going to need to keep trying and find out !

[Jason D]

Seeing is the most critical factor for the "Pup"

Two years ago I took a photo for the Pup using my handheld iphone4.

Jason

[John]

Thats a good indication of how I've found it looks Jason. A glimmer in the diffraction "skirts" of Sirius A 

[AndyWB]

That's what I've been looking for?! No wonder I've not found it yet!

[John]

I've been observing "The Pup" again tonight. I'm working on a sketch of the FoV as I see it, not that my sketching is up to much 

[HumptyMoo]

Well, I promise to like it what ever it looks like

Am hoping this hazy cloud will shift later on. When the neighbours death ray switches off for the night and the people worshipping it go home, then I might get a chance to try some combo's on it (Sirius) to see if I can get some sort of sharp image, or, at least find out the point at which the star starts to flare in the lens.

As for the pup...well I can't even find a galaxy in a candy store right now so that will have to wait

[John]

Well here is my sketch. I did it in pencil then scanned it, reversed the black and white and touched up the stars to get them to approximately the correct relative brightness. 

Sirius B is actually magnitude 11 but seems fainter due to the glow / flare from Sirius A that immerses it. Apart from Sirius A and B there are 4 other field stars in the sketch. The brighter one to the SW of Sirius seems around mag 11 to me but appears brighter than the Pup because it's out of the glare of Sirius A. The other 3 stars shown (you may have to look closely to see them !) are I reckon mag 12.5 and mag 13 or thereabouts. 

The field shown here is what I could see with my 12" F/5.3 Orion Optics dob using a 6mm orthoscopic eyepiece which gives 265x and shows a true field around 9.5 arc minutes across I think (.158 of a degree). 

Finally I ought to say that this sketch represents the best view I got of The Pup star on this occasion. More often it was less distinct or invisible as the flare from Sirius A fluctuated due to constantly varying seeing conditions.

I hope it helps others find this elusive but intriguing little star

[Pig]

Great picture John, it will certainly help   I had a feeling it was around the 3 O'clock position

[HumptyMoo]

As promised

Haze is still pretty bad here, have saved the image for another session, seriously doubt i'll get even close to seeing it but at least I will be 100% certain I am looking in the right spot...unlike those elusive galaxies...either way I have something to aspire to ta muchly

[rory]

Wow that is a close double with the glare factor I can imagine it being a real challenge.

Great sketch john and I'm sure it will give others a reference.

[Qualia]

Great stuff, John and lovely sketch. Really glad to see the sketch up and just wished everyone would try their hand at drawing and share their results. I've tried and tried to split Sirius but I just cannot do it I've tried throwing maximum magnification at it - 250x with the 5mm in the f/5. I've tried using filters (red, variable polariser and even the solar continuum) to dim the image. I've tried on good seeing nights and bad seeing nights and nothing works It's quite frustrating to be honest for on paper it should be an easy split. Do you think I should purchase a x2 Barlow and really go to school on power?

[lukebl]

Great stuff. I have tried with my Meade 12", still without success.

I recall an old article in Sky and Telescope in the 1970s, where someone made a hexagonal aperture mask to put over the front of the OTA which created 6 bold diffraction spikes. This concentrated the glare into the spikes, and you rotated it till the Pup was in position between the spikes, making it easier to see. I shall have a go at that before Sirius disappears for the season and report back.

.......Sirius B is actually magnitude 11 but seems fainter....

My understanding is that is actually around mag 8.5, not 11?

[John]

My understanding is that is actually around mag 8.5, not 11?

You are quite right Luke, it is mag 8.5. Don't know what I was thinking there

The separation between the two is currently around 10 arc seconds I believe which would ordinarily make them an easy split for virtually any scope but Sirius A is around 10 magnitudes brighter than Sirius B making it so much more challenging as the light scatter and flare from A seems to bridge the gap between the two and some more at times, depending on the seeing conditions and optics. Sirius being relatively low in the UK adds to this effect. What I've pictured above is one of the moments of minimal flare and scatter which is when "The Pup" puts in it's clearest appearances.

[Mike73]

Thanks for doing the sketch John.

I dont really have a lot of interest in double stars so at first was going to ask which one is the Pup but then noticed it right next to Sirus A.

Wow thats close!!! I can completely understand why its such a challenging object now!! 

[AlexB67]

Excellent rendition John, I see there are some hidden talents that tell me you should do sketching more often.

Now on the object. I have seen all the 99% of it. Your rendition is an excellent impression of how Sirius A looks in the way I see it through my scope, though the only thing that is missing is the pup in the glare. For me, so close, yet so far. No cigar yet

It is a dog of a split. !!

[chiltonstar]

Lovely sketch John - wish I could draw.

It is pretty much as I see it in my 5" Mak apart from orientation.

Chris

[John]

Lovely sketch John - wish I could draw.

It is pretty much as I see it in my 5" Mak apart from orientation.

Chris

Thanks.

You and your mak are doing seriously well Chris. This is the toughest object I've ever observed I think and my 12" scope, which has very good optics, is right at it's limit on this one. 

[AlexB67]

Thanks.

You and your mak are doing seriously well Chris. This is the toughest object I've ever observed I think and my 12" scope, which has very good optics, is right at it's limit on this one. 

Of course I'll keep trying, but I  wonder if my subpar mirror compared to yours would be a step too far this kind of thing. That  has not stopped me looking though on several occasions to see what I am up against with this task to get an idea  a good ortho or something, a red filter and good site with steady skies there is a little hope one day perhaps.

[Mike73]

It is a dog of a split. !!

hmmm someone pass me my coat!   

[John]

He, he ! 

That pair bring back some memories