Did I split theta Aurigae?

[Zermelo]

I have tried this one before without success, but on Saturday night I thought I might have cracked it - but I'm not sure whether I can tick it off the list.

I was using a 6" newtonian at around 190x magnification, in a Bortle 4 area. Auriga is almost overhead at the moment, and I thought the seeing was OK, though my usual met websites disagreed.  I saw a clear, but very faint, companion at about 300 degrees. It was distinctly clear of the primary's glare, but close enough that it would have been hidden by a diffraction spike, had the OTA been unfavourably oriented. I could see some other faint stars a bit further away.

My app says theta has a +2.6 primary and +7.2 companion, position angle 305 deg and separation around 4".  This much agrees with my view, but the description also says that this is a "very difficult binary to observe visually" and that the secondary can just be glimpsed within the primary's diffraction ring.  This is puzzling, as I've previously managed clear splits down to 2.3" - so my experience tallies more with the data than with the description. Just how difficult is theta Aurigae?

[Jiggy 67]

Looking back at my notes I observed this back in January at x281 mag. I managed a very tight split, so tight I’ve noted it at about 80% sure of success. The secondary was at 11 o’clock and could only be glimpsed in brief periods of good seeing amongst the diffraction spikes of the primary......so I think your observations match mine really........and I’m also not 100% I can mark it off, we could start a club!! ✊😀

[John]

I've just been looking at Theta Aurigae (prompted by your post). It does sound as if you have got it.

I got it at 170x with my 100mm refractor.

Doing the mental conversion between the refractor and the newtonian view, 300 degrees sounds about right and it corresponds with the Stella Doppie database data which says 302 degrees.

I think you got it

It is quite challenging because of the brightness difference between the A and B stars which makes otherwise straightforward separations much harder, eg: Sirius for the most extreme example.

 

 

[Zermelo]

5 minutes ago, John said:

I think you got it

Thanks John.

And no, I've failed with Sirius at least a dozen times!

[John]

3 minutes ago, Zermelo said:

Thanks John.

And no, I've failed with Sirius at least a dozen times!

Took me a long time and, eventually, a 12 inch scope to split Sirius

It's a little easier now (the separation is more or less at it's max) but still a very tough challenge.

Well done on Theta Aurigae though - it's a bit of a "classic"

[John]

Great piece on Theta Aurigae here by John Nansen:

https://bestdoubles.wordpress.com/2012/04/20/theta-aurigae-and-the-light-of-its-passage-is-night-on-the-face-of-the-world/

 

[Zermelo]

12 minutes ago, John said:

Great piece on Theta Aurigae here by John Nansen:

https://bestdoubles.wordpress.com/2012/04/20/theta-aurigae-and-the-light-of-its-passage-is-night-on-the-face-of-the-world/

 

Nice article, I didn't realize it was so noteworthy.

And I hadn't realized about the four components either, so the other fainter stars I saw were probably C and D.

[Soligor Rob]

I feel so much better with myself now after reading these posts. I have been looking at Sirius thinking what am I doing wrong I just haven't managed to observe the split.

I must try harder, mind you a clear sky would help haven't had one here for over a week now.

[John]

5 minutes ago, Soligor Rob said:

I feel so much better with myself now after reading these posts. I have been looking at Sirius thinking what am I doing wrong I just haven't managed to observe the split.

I must try harder, mind you a clear sky would help haven't had one here for over a week now.

It's far from easy Rob. There are many experienced observers around who have not managed it yet.

Like so many astronomical observing challenges, when you have done it once, it gets somewhat easier the next time because you know what to look out for

[Soligor Rob]

11 minutes ago, John said:

It's far from easy Rob. There are many experienced observers around who have not managed it yet.

Like so many astronomical observing challenges, when you have done it once, it gets somewhat easier the next time because you know what to look out for

Thanks for that, could you give me any advice, I have a Sky Watcher 200p Dobsonian, and also a 120mm x 1000mm Refractor.

[John]

17 minutes ago, Soligor Rob said:

Thanks for that, could you give me any advice, I have a Sky Watcher 200p Dobsonian, and also a 120mm x 1000mm Refractor.

I started this thread late last year which may be of use:

 

[Soligor Rob]

Cheers for that John, very informative, gives me something to aim for.

[Sunshine]

The link above is very helpful, thanks for posting, I was looking at “C” component wondering if this was the companion which it is not, I should have been searching for “B” which is much closer. My question is now, how does the position of “B” change relative to its primary as time passes? If I were to search tonight, where should I train my gaze relative to the primary? I understand that at the moment the separation is at a maximum? so I have heard.

Edited March 16, 2021 by Sunshine

[John]

1 hour ago, Sunshine said:

The link above is very helpful, thanks for posting, I was looking at “C” component wondering if this was the companion which it is not, I should have been searching for “B” which is much closer. My question is now, how does the position of “B” change relative to its primary as time passes? If I were to search tonight, where should I train my gaze relative to the primary? I understand that at the moment the separation is at a maximum? so I have heard.

If you are talking about Theta Aurigae, the position of B does change over time, but slowly. The red numbers are years, the grey spot is "now":

[Sunshine]

52 minutes ago, John said:

If you are talking about Theta Aurigae, the position of B does change over time, but slowly. The red numbers are years, the grey spot is "now":

Thanks for the chart, very helpful, just to be sure, the grey spot on the chart represents where Theta Auriga’ companion is, my observation is exactly how my image shows them to be here below. What I saw seems to be correct but, could I have been seeing “C” component? or would “C” Have been elsewhere and unnoticed to me, bottom line is this double confuses me at the moment because I’m not sure if I should be looking for “B” very close to Theta as would appear when observing a tight double like Zeta Her or, is B far from Its parent at the moment that it appears both as is in the chart and, my drawing.

Edited March 16, 2021 by Sunshine

[John]

I've annotated John Nansen's diagram to show the A, B, C and D stars. This is a 5 inch refractor view at 229x as it says. B and C are in the same general direction from A.

Edited March 16, 2021 by John

[Sunshine]

13 minutes ago, John said:

I've annotated John Nansen's diagram to show the A, B, C and D stars. This is a 5 inch refractor view at 229x as it says:

Alrighty, thanks, my confusion was scale it seems, the chart above represents distance of A and B but, when comparing to the image you just provided it seems like it represents positions of A and C.

Having said that, there is never a period in its orbit where B is as far out as C is if i'm correct, B will always appear very close, almost stuck to A no matter where it is in its orbit. 

Correct? C was visible to me but, I wasn't sure if it was just B which was far from A in its orbit, this was my mistake. In a nutshell, when i try this target again, i shouldn't be looking for anything but a tight split, there is no confusing any easily seen stars nearby as "B" , no easy split, it will be tight and tough to split.

Thank you!

Edited March 16, 2021 by Sunshine

[John]

B is about as far from A now as it ever gets. In 2250 or thereabouts it will be less than 1 arc second from A. I won't bother trying for it then

[lunator]

Theta is a tricky split. On a night of good seeing I have split it my 10" scope at x94. 

I have never split sirius at home Houses and their heat plumes always ruin the view.

I have only ever split it from Lucksall.

I am always interested to hear what the lowest mag people can split tricky doubles at.

cheers

Ian

[chiltonstar]

I had a look last night as I had clear sky to the N and W before cloud took over again. Scope was a 180 Mak with a Hyperflex 7.2 to 21.5 mm zoom EP.

Immediately after setting up, the B component was a fuzzy ball in the right position, well clear of the A component. After 10 mins scope equilibration, the fuzzy ball shrank to a diamond point - a very pretty pair. Seeing was good or better, with nearly complete stable diffraction rings for most of the time. The C and D components were very obvious (orientation in the Mak is the same as in the sketch by John Nansen in John's post above.

As the conditions were good and the cloud hadn't yet arrived, I had a look at nearby Struve 799 which is a very close double (0.8 arcsec) - very pretty although faint (mags 7.3, 8.3) with a PA of 162 degrees. Challenging, but certainly split. Another pretty pair I took in nearby is 41 Aurigae, which is a balanced pair with a separation of 7.3 arcsec - looks a bit like a fainter Castor, which is also nearby and glorious.

Chris

[Pixies]

Had a shot at it tonight, using the 8" Bresser dob. Very good seeing tonight.

Split pretty easily, actually. Used the zoom and it was clear at 8mm (150x magnification). Did a sketch of the view using the 7mm UO Ortho (170x mag)

Edited March 19, 2021 by Pixies

[Zermelo]

Update:  I had another look last night and very definitely split it at around 230x, A/B/C components just as I thought the previous time. The seeing seemed to be good last night as I also split the two components of μ² Bootis at 2.2", which is the best I've managed with my 150mm. 

 

 

     

[John]

I got it last night with my ED120. Great seeing last night