Monday, September 07, 2020

imaged 19 Cyg (Halifax)

Here we go. First of a few double star images courtesy the Burke-Gaffney Observatory.

Centred on TYC 3137-0475-1. I wanted to visit 19 Cygni (aka HJ 603), to get C and E stars. I attempted this target in my Ontario backyard on 16 Jun '20 with my C8 and picked off the B and D sparklers.

19 Cyg A is the obvious bright star.

double star 19 Cygni and friends

Luminance filter, 2 seconds subexposures, 12 stacked shots. FITS Liberator, GIMP. North is up; left is east.

Well, C and E are certainly visible, according to SkyTools 3 Professional. But it begs the question: how would one distinguish these from the many field stars?!

B is the brightest nearby star at the 8 o'clock position, a modest distance from the primary. If I had to guess the position angle, maybe 110 to 115°? Easily spotted in the small rendition of the image, zoomed out. ST3P says: PA 112°, separation 56.0", magnitudes 5.2 and 10.4.

The C (natch, see below) companion is north of B, almost perfectly due north. Much fainter. Barely visible zoomed out. Almost on the east diffraction spike. The AB pair PA and sep guesses: 91° and 51". ST3P says the pair information as BC: PA 13°, sep 21.0", mag 10.4 and 11.1. Gonna have to do my SAS triangle calculations for the AB numbers. I think it is much dimmer than 11. It seems closer to mag 13 or 14.

Attendant D is well away, opposite B. It is slightly dimmer than B at 3 to 4 times the distances. ST3P: 312°, 168.6", 5.2, 11.8. Indeed, if D is close to mag 12, C is below that...

The E (blurg, see below) star is the dimmest of all. I have to squint to see it in the zoomed out image. It's obvious zoomed in, between A and D, almost perfectly in-line, but is dimmer than C. The planning software says this about AE: 322°, 102.8", 5.2, 12.6.

Some of those numbers in SkyTools are wonky.

From Stella Doppie. All data no older than 2014.

AB: 115, 56.8, 5.38, 10.54
AC: 318, 96.6, 5.38, 12.60
AD: 309, 163.8, 5.38, 11.90
BC: 309, 150.5, 10.54, 12.60 (a curious cross-check)
BE: 11, 20.8, 10.54, 13.50

Oh, oh. The labels are different. SD says B and E are to the south-east and C and D are NW. That's a flip of C and E...

Weird. They say E is the dimmest. Nope.

stars around 19 Cyg plotted

The E star (new) is nearly 90°. I had guessed 91. My SAS calculation says 93° with a derived separation of 55.6".

So this was a good imaging task. It plucked out the C and E stars, revealing they are very faint. Near the magnitude limit of the 8" Schmidt. I don't recall the conditions but they'd need to be pretty good to get these comrades. But, again, it might prove challenging, without the aid of good software, to know the associates from surrounding field stars.

The "undesignated" pair I noted 3 months ago is obvious, to the north-east, oriented north-south, same separation as BE. In fact, the same position angle as BE.

One could easily argue there are many double stars here.

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