Author Topic: challenging double double in Hercules  (Read 236 times)


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challenging double double in Hercules
« on: August 28, 2017, 01:15:59 PM »
These last few nights have had really good seeing, and I've been chasing doubles in Hercules (my yard has a better view to the west, so that's where I'm usually looking).  12.5-inch f/7, 553x

There were many "wow" objects, of which following is a selection.  I end below with a challenging "double-double" I feel really lucky to have seen:

STF 2107: !! Plotted in Cambridge Double Star Atlas, and I didn't expect it to be special.  Yellow and orange pair, very close ~1.5", 1 delta mag.  Very pretty. [AB seen, AC nearly 12th mag and super wide]
16H 51M 50.10S +28° 39' 58.7" P.A. 106 SEP 1.39 MAG 6.90,8.50 SP F5IV DIST. 58.41 PC (190.53 L.Y.)

STF 2095: Nice!  Yellow and white pair, 2 delta mag, 4"
16H 45M 05.23S +28° 21' 28.9" P.A. 163 SEP 5.2 MAG 7.36,9.16 SP F7III DIST. 215.98 PC (704.53 L.Y.)

STF 2103: Nice! Pretty bright white A, much fainter ~5 delta mag B, well separated, looks like a planet. [AB seen.  AC & AD fainter and wider]
16H 49M 34.67S +13° 15' 40.3" P.A. 44 SEP 5.2 MAG 5.93,10.00 SP A1V DIST. 100.1 PC (326.53 L.Y.)

52 Her = BU 627:  !! Very bright white star with a companion disk 2” out, 4-5 delta mag.  Wow!  B illuminated by A, as if it was a planet.  [A,BC seen.  BC is an equal pair only 0.3” separation – maybe try with the 20-inch.  7 stars total in the system.]
16H 49M 14.21S +45° 58' 59.9" P.A. 39.6 SEP 2.09 MAG 4.84,8.45 SP A1V DIST. 55.25 PC (180.23 L.Y.)

D15: Light orange & elongated with notch, near equal.  [0.9” at discovery, 0.56” now]
16H 43M 56.29S +43° 28' 31.2" P.A. 332.8 SEP 0.56 MAG 9.04,9.27 SP K5 DIST. 27.03 PC (88.17 L.Y.)

HO 557: !! B only visible with averted vision.  As I drift from averted back to direct the star fades and I can only hold direct for a moment before it disappears.  Very interesting effect.  ~5” and 4 delta mag.
17H 13M 57.81S +16° 21' 01.0" P.A. 322 SEP 4.2 MAG 8.57,12.00 SP F8 DIST. 106.27 PC (346.65 L.Y.)

PRY 2: Blue-white and slightly reddish B, 3-4 delta mag, 1.5”.  Not hard at all!
17H 04M 41.34S +19° 35' 56.7" P.A. 227 SEP 1.8 MAG 6.19,9.29 SP A0IV DIST. 176.68 PC (576.33 L.Y.)

BU 822: Bright orange star with a consistent pin-prick point of light, stays still in occasional seeing shimmer.  Fainter than PRY 2's B.  1.5”.  Same PA as PRY 2's.  [AB seen; AC is super-wide & 11th mag]
17H 03M 52.67S +19° 41' 25.8" P.A. 227 SEP 1.4 MAG 6.58,9.89 SP K4III DIST. 229.89 PC (749.9 L.Y.)

These last two are close enough together I tried them as a double-double.  The trick is to maintain enough magnification to be able to keep the splits.  I went down to 277x 0.4° TFOV and could just squeeze the two within the field stop.  PRY 2 remained a very clean / clear split, while BU 822 was more challenging due to B being half magnitude fainter and slightly closer separation than the PRY 2 pair.  I could split BU 822 at 277x when in the center of the field, but I needed to wait for seeing to perfect and to bring it in a little from the field stop to avoid edge distortion.  But, for a few moments, I had these two in view as a double-double.  I'll try this again at CalStar in the 20-inch, it should resolve nicely.  Given the distance between the two pairs, they are just a line of sight double-double, but nice all the same.
« Last Edit: August 28, 2017, 04:25:41 PM by mccarthymark »