Sirius B with a budget 102mm ED refractor ! (and a budget mount)

[Nik271]

Last night I had excellent seeing on Sirius, totally unexpected. 

My plan was to try to see some detail in the Rosette Nebula with OIII filter and my widefiled scope, a Svbony 102mm ED refractor. I bought this two years ago for widefield so did not expect it to be good on planets - it uses FPL51 glass so at very high mags (180 and above) there is a bit of colour on bright objects. Actually it turned out ot be a decent performer on planets, close but not quite equal to my 127 Skywatcher Mak.

The sky was beautifully clear at 5pm but by 9pm when I set up there was a thin layer of haze. Rosette, a difficult target from my sky at best of times, was totally invisible, so change of plan was needed. On a whim I swung to the nearby Christmas tree cluster. The brightest star  there, S Mon, is a tough double ( just under 3'' separation and 3 magnitudes difference between the primary to secondary). With a 4mm Nirvana giving x180 I had no trouble splitting it. The seeing was extremely good, the primary dispalying a perfect diffraction pattern with the secondary nesting next to it.

This is when I regretted that I haven't taken out a  larger aperture scope on the EQ5. Instead I had the 4 inch refractor on AZ5  on an adapted surveyor tripod, good for grab and go but not ideal for high mags. But it was too cold to fiddle with cold metal when changing scopes. So the refractor had to be.

After a quick look at my other test for Sirius: Alnitak and confirming it was an easy split in the seeing I swung down to Sirius who was just showing over the rooftop. Immediately I recognized I was in luck: Sirius was steady and  displaying multiple diffraction rings, surrounded by a faint violet halo (FPL51 doublet, no surpises here). After relaxing my eye and manually tracking with frozen fingers I became convinced that I see a faint dot about north east of Sirius. To make sure I switched to a 3mm LER and the Pup was easier to see, popping in and out of my vision. It is no longer directly following the primary but it has moved further north of east. I have had easier splits but with larger scopes. So this is my personal best for smallest aperture showing the Pup 🙂 It just goes to show that seeing is king for splitting doubles, especially for Sirius.

 

Here is a picture of my new Sirius B spotter scope. It's waiting for a gap in clouds 🙂

 

  

Clear skies!

 

Nik

 

[cajen2]

Nice one! Must try that with my Starfield 102 ED.

[Nikolai De Silva]

What is minimum size for a Newtonian to see the pup star? I have a SW 130p.

[John]

Excellent result Nik 🙂

I got very occasional glimpses of the Pup last night with my Tak 100 but it was hard work !

 

[John]

Just now, Nikolai De Silva said:

What is minimum size for a Newtonian to see the pup star? I have a SW 130p.

Sirius is much higher in the sky for you that it is here in the UK so your 130P may well show it reasonably easily. Yon need 200x or more, as little scatter as possible and as steady seeing as possible. The gap between Sirius A and B is around the same as Rigel and it's companion star so you can practice on that and see how that goes 🙂

The big challenge is that Sirius A is appears 10,000 brighter than Sirius B so the dimmer star gets drowned out in the glare of the brighter one.

[Nikolai De Silva]

Thank you very much @John! I'll surely try it.

[Epick Crom]

Congratulations Nik on seeing the Pup with 4 inches of aperture 👍

[Nikolai De Silva]

Hello @John this was what I got. Is this the pup star?

 

[Mr Spock]

I've found I can get the pup with a 4" - but only in excellent seeing. With Sirius seeing is always the limiting factor.

[John]

41 minutes ago, Nikolai De Silva said:

Hello @John this was what I got. Is this the pup star?

 

I'll be honest and say that I think it is unlikely. Sirius B visually appears within the glare from Sirius A and that is for visual observing when using low scatter optics at around 250x magnification or more. The camera will be adding glare to the star as well I think.

I did a sketch a while back of the view of Sirius A and the Pup star and the surrounding visual stars with a 120mm refractor at 257x magnification. North will be at the bottom with your scope (a newtonian ?) but these other stars will be visible if the Pup star is to be seen:

 

[Nik271]

This article has photos of Sirius B which shows what to expect. The glare of Sirius A makes imaging the secondary very hard.

https://skyandtelescope.org/observing/sirius-b-a-new-pup-in-my-life/

[Nik271]

23 hours ago, Nikolai De Silva said:

What is minimum size for a Newtonian to see the pup star? I have a SW 130p.

In Sri Lanka you will have an easier time since Sirius rises quite high. Wait until it is at least 50-60 degrees above the horizon and choose a night of good seeing. Use magnification of at least x200. Your 130mm Newtonian, if well collimated should show it, just make sure the Pup is not obscured behind a diffraction spike.