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SkySafari Pro nomenclature question

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#1 mbhnm

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Posted 08 June 2021 - 03:20 PM

Example: When I am using Skysafari Pro it shows: Mizar A 0.8”. When I go to the info page it lists: Separation 0.8” at 214.9 degrees. I would assume this means that Alcor is .8 arc seconds away and located at 214 degrees right declension. But when I read the accompanying notes they say Mizar and Alcor are separated by 11.8” So I seem to have something wrong and have not been able to find any explanation. If someone could enlighten me I would appreciate it. If the 0.8” is not the separation distance between Mizar and Alcor, what is it? And why does a similar designation show up for most double stars (ie: Kochab 214.1”). Thanks!



#2 mbhnm

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Posted 08 June 2021 - 03:23 PM

Forgot to add, my version is 6.8.5.2.



#3 jc482p

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Posted 08 June 2021 - 03:36 PM

Looks like the description is saying the separation of 11.8” is between Mizar and Alcor, whereas the info page is saying the separation of 0.8” is between Mizar A and Mizar B.  Mizar by itself, without Alcor, is a double star system.


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#4 mbhnm

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Posted 08 June 2021 - 03:52 PM

That is possible, but further down in the notes it indicates that Mizar A and B are 14” apart. At least that is how I read it. You are probably right that the separation listed is between A and B even though most of the discussion is about Mizar and Alcor. The discussion is certainly not clear, at least to me, and makes me wonder if I am off track somewhere.



#5 hcf

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Posted 08 June 2021 - 04:29 PM

Is it 11.8" (arc-sec) or 11.8' (arc-min)? 

 

SS6 Pro says the latter.

 

https://en.wikipedia.org/wiki/Mizar

 

From what I read:

 

Mizar A and B (not Alcor) have 14" (arc-sec) separation. Each of them are binaries (Aa Ab Ba Bb).

I am guessing Sky Safari says the Mizar A double is actually Mizar Aa and Ab have 0.8" (arc-sec) separation.



#6 mbhnm

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Posted 08 June 2021 - 06:55 PM

That sounds correct. I miss typed 11.8” instead of 11.8’. That should be Mizar A and Alcor. The 14” is probably Mizar A and B and the 0.8” Mizar Aa and Ab. Seems I read that Alcor may also have a double as well, a complicated little group. I think that clears it up in my mind and will give me a clearer idea of what to look for. Looks like the best I can hope for with my scopes is to see Mizar A and Alcor with maybe Mizar B on a clear night. Thanks!



#7 sanbai

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Posted 08 June 2021 - 10:30 PM

My guess it's that there's a kind of automatic value in the data tab. Some stars have listed separations that I would not consider "double star", especially with the magnitude difference. I would say even the description tab may automatically tell you a about that separation based on some algorithm and the proximity of stars rather than a double star catalog information. This happens with many bright stars there.


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