Two Alulas: The Bears Hind Paw

[John]

Mainly double star observing this evening with my 130mm refractor.

Over Leo's hind quarters are a pair of stars which are actually part of Ursa Major. The bears hind paw in fact.

Their proper names are Xi Ursae Majoris and Nu Ursae Majoris. Their other names (which I much prefer) are Alula Australis (Xi) and Alula Borealis (Nu). They sound quite exotic !

Here they are:

Both these Alulas are double stars but rather different ones through the scope eyepiece.

Alula Australis is a splendid magnitude 4 golden-yellow pair with a separation of 2.16 arc seconds (Stella Doppie database). Very attractive indeed.

Alula Borealis is also a pair but with a large brightness difference. The primary is magnitude 3.6 and the secondary star a rather dim magnitude 10.10. The separation is 7.5 arc seconds but seeing the 10th magnitude secondary star can be a ticklish business because of the brighness difference. Tonight the 130mm refractor showed them both quite nicely at high magnification.

Both well worth seeking out IMHO.

As Gene Vincent sang "Well, Be Bop Alula ....." or something like that !

 

Edited March 17, 2021 by John

[Pixies]

I'm collimating and star-testing my old Skymax90 before I sell it shortly. I might aim it at these two and get some use out of it, one last time.

[Pixies]

Yep - managed to get Alula Australis. In the Skymax90, with 15mm (x80) with very good seeing tonight.

Alula Borealis - no luck. I was planning to stay longer on it with some higher powers, but the clouds rolled in.

[John]

10 minutes ago, Pixies said:

Yep - managed to get Alula Australis. In the Skymax90, with 15mm (x80) with very good seeing tonight.

Alula Borealis - no luck. I was planning to stay longer on it with some higher powers, but the clouds rolled in.

Good result with Alula Australis

The mag 10 component of Alula Borealis was pretty faint with my 130mm. I missed it initially and it only became apparent after I studied the star for a while.

 

Edited March 18, 2021 by John

[Nik271]

Thank you @John! These look an interesting pair of doubles and well placed right now in the evening sky. I will check them out next time. Looks like Alula Borealis may need my big 180 SW Mak, not sure my 127 Mak will be up to splitting 10 mag stars,  considering it's aperture is only 119mm.

[John]

1 hour ago, Nik271 said:

Thank you @John! These look an interesting pair of doubles and well placed right now in the evening sky. I will check them out next time. Looks like Alula Borealis may need my big 180 SW Mak, not sure my 127 Mak will be up to splitting 10 mag stars,  considering it's aperture is only 119mm.

The brighter component of Alula Borealis is mag 3.6, it's the secondary star that is a challenge. Normally your mak should show mag 10 stars without too much of a problem I would think but the proximity to the brighter star may hamper that. 

Edited March 18, 2021 by John

[Nik271]

I managed to split both of them last night with the Skymax180, against all odds, since it was 80% cloudy

It all started as a Moon session initially since the Moon was punching through the high cloud, but after  some time I remembered @John' s post and turned the scope  east towards the Alulas. Amazingly I could see them through the cloud in the finder so I centered on each one of them in turn and waited for a gap in the clouds.

I still had the 15mm EP in the scope, which gives me 180x and it was perfect for both. Alula Borealis was trickier - the secondary was very dim and was constantly winking in and out as thin cloud was passing. I put its the position somewhere southeast of the primary. The Alula Australis while a much closer double was actually easier, as both component are fairly bright. 

That was nice, worth another visit in a clear night!  

[Epick Crom]

On 18/03/2021 at 07:36, John said:

Mainly double star observing this evening with my 130mm refractor.

Over Leo's hind quarters are a pair of stars which are actually part of Ursa Major. The bears hind paw in fact.

Their proper names are Xi Ursae Majoris and Nu Ursae Majoris. Their other names (which I much prefer) are Alula Australis (Xi) and Alula Borealis (Nu). They sound quite exotic !

Here they are:

Both these Alulas are double stars but rather different ones through the scope eyepiece.

Alula Australis is a splendid magnitude 4 golden-yellow pair with a separation of 2.16 arc seconds (Stella Doppie database). Very attractive indeed.

Alula Borealis is also a pair but with a large brightness difference. The primary is magnitude 3.6 and the secondary star a rather dim magnitude 10.10. The separation is 7.5 arc seconds but seeing the 10th magnitude secondary star can be a ticklish business because of the brighness difference. Tonight the 130mm refractor showed them both quite nicely at high magnification.

Both well worth seeking out IMHO.

As Gene Vincent sang "Well, Be Bop Alula ....." or something like that !

 

Interesting report John. I think those double stars are just visible for me here Down Under. I will search for them soon. Thanks for making me aware of them! Clear skies