Beta Delphinus double star challenge

Had a most enjoyable evening looking at double stars in Delphinus. After the delightful and easy double star gamma Del, there are some lesser known double stars in this small constellation that are very rewarding. On this occasion Beta Delphinus , which threw up a couple of nice surprises.

A little history first. According to the Bedford catalogue 1834 this is a most delicate (triple) star of mags 4, 12 and 15. But neither Sir William or Struve saw this as a triple. So as with many early observations, with lesser instruments to that of today, there were many conflicting observation reports,  positioning , separations and magnitudes. But nevertheless a very interesting book.

So on to modern times. We now know this to be a double star of mags 4 and 11, with a separation of 42 arc seconds. So using the 12″ Dobsonian with the Vixen NLW 22mm eyepiece (68x) I centred the object. Despite the wide range of brightness, the wide gap made this an easy double star to split, due to the dimmer star being out the range of the primary. Maybe not a WOW factor double, but very rewarding to see.

But the main and most unexpected reward was the wider view. I could also see the slightly fainter Zeta Delphinus in the same FOV. But my eyes were drawn to a lovely triangle of 8th mag stars in the centre of view, which seemed to have a blue / green tint to them. Looking further into this, I found the top two in the triangle (upside down view through the scope) were in fact another double. The stars are HIP 10700a and HIP 10698b with near equal mags of 8.30 and 8.25. This is a nice wide gap and easy for any telescope. The 3rd star in the small group was HIP 101694, mag 8.65.  So after trying for one double star, I got another one free of charge in the same view. There were also a number of other stars around 10-11th mag to the North of the field, which nearly looked like a mini Delphinus 

Go out and try this lovely grouping of stars for yourself on a clear night. A good scope of 3″ or larger will be needed to see the fainter companion of Beta Delphinus

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