Friday, October 05, 2018

imaged zeta Sge (Halifax)

When the Clear Sky Alarm Clock notification arrived for the Burke-Gaffney Observatory, I was not surprised. The clear weather over Ontario last evening was due at the east coast. Average transparency but poor seeing. Still I opened up Danko's weather resource for Halifax. Later I opened the Twitter feed. Looked like the St Mary's University robot was up and running. There were some clouds but the imaging system pressed on.

I captured the multi-star system ζ (zeta) Sagittae aka AGC 11 and/or Σ2585 (aiming at TYC 01623-2382 1) . SkyTools 3 Professional shows it has 4 elements.

This request was to resolve a couple of issues with this previously logged item. My life list entry going back to 2008 appears to have a typographical error for the separation. Also I have never noted the easy D element.

zeta Sagittae in luminance

Luminance only, ½ second subexposure, 20 stacked shots. FITS Liberator, Paint.NET. North is up; east is left.

The A and C stars are obvious with bright C touching A at the 2 o'clock position or to the north-west. ST3P quotes the angular separation at 8.3" with a position angle of 310°. The D element, happily, is visible is this image. That said, it is remarkably faint when compared to A and C. It is the next brightest star well away to the west-south-west. Perhaps 10 or a dozen times the AC split distance (77.4"). ST3P says it is magnitude 11.8. zeta Sge is in a lovely field.

By the way, the B star, a rapid binary with a 23 year period, was at a calculated separation of 0.2".

I took red, green, and blue data as well, at three times the duration of the clear exposure. It will be interesting to see the results when the colour channels are applied.

First viewed this target on 5 Jul '08 quickly noting the colours. I believe when I placed the entry in my life list, I copied from the row above, and forgot to edit the separation value from 1.6 (from lambda Oph). Sissy Haas notes the split as 8.3 seconds of arc. My 10 Jul '10 observation added nothing. It is nice to tidy this up.


Wikipedia link: zeta Sagittae.

No comments: