Telescope Reviews: Dbls in Oph, Ser, Scu and two close challeng dbls

Sunday night Aug 31, 2003

Along with a few doubles in Ophiuchus, Serpens and Scutum, I revisited two doubles from last week. This night all were tried with just the TV85mm/600mm.

For several, I determined the minimum magnification needed to split. The apparent separation is the image size that allows my eyes to see the separation. When not approaching the limits of the telescope aperture, this can be a good indicator of the observer’s visual acuity. Closer doubles, those with a brighter primary star and fainter pairs all generally require a greater apparent separation to see the split.

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TV85ref 85mm(3.35”)/f=600mm Ray Lim 5.45/3.35=1.63” Daw Lim 4.56/3.35=1.36”

Lim Mag south 4.8 direct, 5.2 and 5.8 averted Transparency very good. Seeing very good.

70 Oph 4.2-6.0 / 4.4” Vis Bin PA142
17mm Sirius plossl 35x not seen; 11mm TV plossl 55x clearly split. Probably should have tried a few eyepieces in between to get a read on min required mag to split. Apparent sep = 242 arcsec.

69 Tau Oph 5.2-5.9 / 1.7” Vis Bin PA285
11mmTVpl and 6mmUO ortho not seen, 2xTVbarlow 9mmUO 134x elongated, 2xTV 8mmTVpl longer elongation, 2xTV 7.5mmTakLE 160x two orbs seen but not separated, 2xTV6UOortho 200x split looked like a thin line. Apparent sep = 340 arcsec.

E2373 Scutum 7.2-8.2 / 4.2” PA338
Located 1° south of M26. 7.5TakLE 80x see f* is N preceeding, very close clear split. Looked wider, only slightly more so, than 69Oph 1.7” did at 200x. Did not determine min required mag for split. Apparent sep = 336 arcsec.

E2375 Serpens 6.9x2-7.9x2 / 2.5” PA118
Tweedledee / Tweedledum, located half way between Alya, 63 theta Ser and oc I4756. AB and CD are both doubles, but both have separations of only 0.1”, maybe a Hubble double-double. AB-CD makes a nice easy 2.5” double. 7.5TakLE 80x just barely seen split clean; 5UO 120x split wider. Apparent sep = 200 arcsec.

52 Pi Aquilae 6.1-6.9 / 1.4” PA110
7.5TakLE 80x tiny, elongation suspected; 5UO 120x still tiny but elongation definite; 2xTV9UO still just elongated; 2xTV8mmTV 150x elongated point f* following; 2xTV7UO 172x clearly elongated with f* following; 2xTV6UO 200x notched just barely touching; 2xTV5UO 240x clearly see b*f* but they still touch. The 85mm scope may have reached the limit of its aperture with this close double. This observation was better than last week, and still I was not able to reach a clean split. Best was 240x = Apparent sep = 336 arcsec

Z Aquarii 4.3-4.5 / 2.2” PA188
7.5TakLE 80x not seen; 6UO 100x two components just touch; 5UO 120x split with thin black line.
Apparent sep = 264 arcsec

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