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unequal pairs, angular separation and ease of "splitting"

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#1 Pete W

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Posted 06 January 2020 - 03:28 PM

Last night I stumbled upon a trio of doubles in Taurus that nicely illustrated how the ease of splitting unequal pairs in a small scope is dependent on angular separation:

S461
STF 623
STF 645

 

Screen Shot 2020-01-06 at 2.23.03 PM.png

 

In all three the primary is roughly mag 6 and the secondary is roughly mag 8.5, but the separation decreases from 78” in S461 to 21” in Struve 623 and then 11” in Struve 645.   All three are just to the west of beta Tau (the northern horn star in Taurus) so it was quick to jump from one to another.  

 

It was quite apparent in my 60mm f/15 at 121X that as the separation tightened the less obvious they were split.  Not a profound revelation, but still neat to see.


Edited by Pete W, 06 January 2020 - 03:28 PM.

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#2 DeWayne

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Posted 06 January 2020 - 03:32 PM

Well, I know what im looking for tonight.   Lemme grab my 60mm f/15 from the basement....wink.gif

 

Thanks for sharing!


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#3 John Fitzgerald

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Posted 10 January 2020 - 10:39 PM

Yes, that is typical.  Unequal doubles have been an interest of mine for several years.  I have looked at very many of them.  The Dawes limit does not apply there.  Otherwise, Eta Draconis, Sirius, Adhara, and Antares would be easy splits in small telescopes.

 

Good seeing is very important when looking for faint companions near brighter primaries.  In bad seeing, the images swell, move, and dim, making fainter secondaries invisible, despite sufficient separation otherwise.


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