Sirius and Pup separation over the years

[CraigT82]

6 hours ago, markse68 said:

It must be too faint for an 8” scope under Bortle 9 skies I guess. Still it was a really great night and an enjoyable if frustrating challenge. 

I also had a quick go last night with the Fullerscope and couldnt manage the split, though I have managed it previously with this scope though.

Sirius is pretty low down and with all the people with their heating on I think the local seeing was pretty poor.  Just got to keep trying!

In my bortle 8 skies my limit with the fullerscope is about mag 11.5 IIRC. 

[John]

The "Pup", Sirius B is magnitude 8.44. It's the huge brightness difference between it and Sirius A plus the relatively close separation (around 10 arc seconds) and it's low altitude from here in the UK that make it very challenging.

I have seen Sirius B with both my 12 inch dob (reasonably often) and my 130mm triplet refractor (less often) at around 250x - 300x magnification. It was not to be last night with the 130mm refractor though, although I may have had fleeting glimpses of the B star from time to time. Nothing certain enough the claim the split.

I did check the field stars with the 130mm refractor and they matched those that are in my sketch although N & S were reversed in the refractor of course.

If Sirius was higher in the sky, especially on these winter nights with all the central heating around, it would split somewhat easier. If your view of the star is across open fields, moorland etc rather than any housing that would help as well.

As Craig says, you just have to keep trying and one night things will come together.

 

 

[John]

This Sky & Telescope article was written a couple of years back but is relevant:

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

 

 

[John]

I've found this oberving sketch done by another observer in 2014 using a 10 inch scope at 280x. The observation location was Mobile, Alabama and therefore Sirius higher in the sky than it gets here but, allowing for the slightly larger field of view in this sketch, the field stars look recognisable although I have one in a slightly different position - I'm not a regular sketcher !

Here are the two sketches (mine is the cruder looking one and dated 2019 !):

 

 

[markse68]

4 hours ago, CraigT82 said:

I also had a quick go last night with the Fullerscope and couldnt manage the split, though I have managed it previously with this scope though.

Sirius is pretty low down and with all the people with their heating on I think the local seeing was pretty poor.  Just got to keep trying!

In my bortle 8 skies my limit with the fullerscope is about mag 11.5 IIRC. 

Thanks for the encouragement Craig- good to know that it should be possible with my scope and my sky.

How did you go about establishing the magnitude cutoff for your scope? Just look for known magnitude stars incrementing  till you can’t see them?

[markse68]

3 hours ago, John said:

I did check the field stars with the 130mm refractor and they matched those that are in my sketch although N & S were reversed in the refractor of course.

As Craig says, you just have to keep trying and one night things will come together

This is strange- I guess you’re seeing these field stars

 

but I’m seeing maybe some of these 🤷‍♂️

 

Anyway- yes I’ll keep on trying 😊

 

 

Edited January 21, 2020 by markse68

[CraigT82]

55 minutes ago, markse68 said:

How did you go about establishing the magnitude cutoff for your scope? Just look for known magnitude stars incrementing  till you can’t see them?

Yes pretty much! Well I just picked a spot on the sky and pointed the scope at it, found that same view in skysafari and checked the app to see what mag the faintest stars were that I could see through the scope. Repeat a couple of times with different EPs and different parts of the sky to get a general feel for the limit. 

[John]

This will sound odd but I don't find apps a reliable guide to what can actually be seen in the eyepiece. Those other stars are definitely not visible even with my 12 inch dob and that will go down to mag 14.7 point sources.

 

[Stu]

18 minutes ago, John said:

This will sound odd but I don't find apps a reliable guide to what can actually be seen in the eyepiece. Those other stars are definitely not visible even with my 12 inch dob and that will go down to mag 14.7 point sources.

 

I usually find Skysafari very accurate in that you can set the field of view and limiting magnitude to match what you are seeing through the eyepiece. I can sort of see a match between the sketches but there are some differences. Will try to match up with what I see through my scope next time out.

[John]

That would be good

The true field shown in my sketch is .22 of a degree and its newt orientated (obviously).

If it stays clear I'll have my 12 inch dob out later tonight and re-check my sketch, again.

 

 

 

 

[John]

Hmmm - clear all day, now clouds

 

[Stu]

28 minutes ago, John said:

Hmmm - clear all day, now clouds

 

Clear here but I'm pretty tired and I doubt a third session on the trot would go down very well!

[Wiu-Wiu]

Here's a sketch by a friend in a 10" dob:

 

You need to beware that the pup often hides right next to a spike. Maybe that's what's throwing you off? 

[markse68]

53 minutes ago, Wiu-Wiu said:

Here's a sketch by a friend in a 10" dob:

 

You need to beware that the pup often hides right next to a spike. Maybe that's what's throwing you off? 

Hi Wiu -Wiu, yes I had heard that and as a consequence rotated my scope tube several times during the evening in an attempt to avoid it- I don’t think it was hiding in a spike but maybe- maybe I managed to rotate it exactly 90 degrees each time 🤔

[John]

We seem to have some consistency in the sketches. Mine has the smallest true field because of the longer focal length scope and higher magnification but mark my approx field on Wiu-Wiu's friends image and rotate it and you get a reasonable correlation:

 

[Geoff Barnes]

I'm pretty certain that it is the low altitude and poor seeing conditions that are causing the problems for all you poor folk up north.

I wouldn't say it was easy, but I rarely failed to spot the pup whenever I tried last year with my 12 inch Dob, with Sirius being quite high in the sky down here. Apart from the glare of Sirius I found the diffraction spikes to be my main obstacle to overcome.

Edited January 21, 2020 by Geoff Barnes