Unknown star (Skysafari problem)

[Richard N]

I'm a new user of Skysafari and I used it for just the second time last night. It was pretty cloudy but some of Ursa Major was visible so I looked at my favourites, Mizar and Alcor. I usually use very low power for this pair but as I had a new 5mm eyepiece I tried that out. I was immediately surprised to see that Mizar itself split into a pair. I wasn't expecting that. However looking at Skysafari on my iphone the pair displayed were 0.6" apart. That was well beyond the resolution of my telescope. Being new I wondered if this "unknown" pair was some sort of artefact of my cheap ST80 but that didn't seem likely. Reading the Skysafari information on Mizar it did refer to a 14" double which would fit in, but the display did not show it. Searching for an answer today I find that this is a long-standing Skysafari issue. That's disappointing and has knocked my confidence in the app. As a naive beginner, I did kind of expect these apps to get the basics right (especially in such a prominent pairing). Should I be expecting more disappointment with Skysafari or is this a one-off?

Edited August 7, 2021 by Richard N

[AstroNebulee]

Hi Richard 

I have looked on sky safari 6 pro and can see Zeta Ursae Majoris B. But not the companion star to the south east of Mizar. In stellarium I can see ZUM B and then zooming in closer I can see the unknown star to the south east (see stellarium screenshot) is this the star you saw? And below that screenshot from SS6. 

Edited August 7, 2021 by AstroNebulee

[Richard N]

This is what I saw and this is what SS 6 Plus shows. SS6+ appears to have no knowledge of the wider Mizar pair. A quick search on the web shows this problem has been known since 2018. 

Edited August 7, 2021 by Richard N

[Richard N]

Stellarium is fine in this respect.  

[Pixies]

Very odd. In Stellarium on my laptop, it doesn't show. But it links Mizar with Alcor, and doesn't show the seperation with its close double.

[Richard N]

21 minutes ago, Pixies said:

Very odd. In Stellarium on my laptop, it doesn't show. But it links Mizar with Alcor, and doesn't show the seperation with its close double.

You probably need to reduce the star brightness to show it in Stellarium. I had to. That’s not the problem with SS6+ though. 

[Pixies]

17 minutes ago, Richard N said:

You probably need to reduce the star brightness to show it in Stellarium. I had to. That’s not the problem with SS6+ though. 

Yep, thanks. It shows the star, but the info is still different.

But yes, Sky Safari has an issue with it. There are several threads on Cloudy Nights about it too, as well as the Sky safari support pages. I've never come across a missing star in SS before, but I guess this must be linked to whatever data model they use to store multiple star systems. I do recall finding a mistake in angular seperation once before, though.

[Richard N]

17 minutes ago, Pixies said:

Yep, thanks. It shows the star, but the info is still different.

But yes, Sky Safari has an issue with it. There are several threads on Cloudy Nights about it too, as well as the Sky safari support pages. I've never come across a missing star in SS before, but I guess this must be linked to whatever data model they use to store multiple star systems. I do recall finding a mistake in angular seperation once before, though.

It's weird that SS have been unable to fix it. I thought I had spotted a supernova for a minute!