Stars of Ursa Major.

We’re lucky that the largest open cluster is rising , the main stars form a moving cluster , except for the first and last ones. A good sign of atmosphere is to check Mizar / Alcor splits by eye. The easiest targets are the stars here,
Stars of UMa.

Dubhe (α) is a very wide orange and brown pair at low magnification.However the α itself is a very close binary, best I’ve had is a bright donut shape at .8″. It is the furthest of the dipper stars and not one of the five cluster stars.

Mizar and Alcor are optical doubles, the bright one , Mizar opening out to give a 14.3″ split.

Talitha (ι UMa) shows a white and a close 4.5″ blue, I found this quite a challenge.

Σ1523 (53 UMa, xi )(Alula Australis), a superb widening binary 1.7″ at +4.3 +4.8 with an orbit of 59.8 years. This was the first ever binary discovered on 2nd of May 1780 by Sir William Herschel and the first visual double for which the orbit was found. A very beautiful sight.
To the north is Lalande 21185 a red dwarf +7.5 at 11h30.3m. +35 58’11”. This is the fourth closest star and nearest planetary system at 8.32 lys.
Next door is Groombridge 1830 (Argelander’s Star) the third fastest proper motion star , moving one degree every 511 years. At +6.4 go to 11h52.9m. +37 43′.

Some colours and showcases now,
Σ1193 shows a wide orange and blue at x50.
23 UMa shows yellow and green, there is a third element at 100″ being +10.5.
Σ1415 shows a pair at 16.5″.
Σ1495 between Merak and Dubhe shows an easy wide lovely pair.
h 2554 is a wide 40″ with plenty colour here.
57 UMa a lovely white and blue at x100.
Σ1559 I use as a tester, a lovely delicate companion at 1.8″.
65 UMa is a colourful triple , worth a long look.
Σ1603 gives a lonely pair of headlights at x50.
Σ1695 gives a lot of colour at 3.8″. As does the blue companion of
78 UMa at a close 1.2″.
Σ1770 , a most delicate pair, but I caught it in the 102. More colour at
Σ1795 at 7.9″. I’ll end with the very delicate
Σ1831 an arc of a triple at x50.

some observations here with coordinates or SAO details in Synscan handsets.


I found a scribble suggesting that the optimum magnification for observing binaries is 750 divided by the arc seconds. That combined with your maximum magnification being your aperture in inches x50, food for thought. Hopefully under the
Clearest skies !
Old Nick.

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