Saturday, August 20, 2022

imaged neglected double STI 2505 (Halifax)

I asked the BGO Robotic Telescope to aim to a part of the sky in Cygnus to get data on a neglected double star.

According to the Washington Double Star database, STI 2505 has only been observed twice, first in 1903 and then in 1917. Data over 100 years old. The most recent position angle is 15; separation 10.2. Faint pair at mags 11.9 and 13.2. No spectroscopic values. 

I initially tried to use the Tycho designation 03940-0251 1 but it was not found in the BGO catalogues. Stelle Doppie did not have any other label except the Gaia. So I used the WDS code. No problemo.

The Burke-Gaffney Observatory returned the following.

region around STI 2505 in luminance

FITS Liberator, GIMP. North is up; east is left. Luminance, 1 second, stack of 12 exposures. Magnitude depth approximate 16.

There's the obvious wide pair near the centre of the image. The upper (north) star is the target, STI 2505. There should be a tighter, fainter star to the north-north-east. Nope...

The faint star to the NNE is J200903.8+554640, mag 14.3. It is actually along the same angle. So the B star of STI 2505 should be between. And B should be slightly brighter. Nope.

I checked the R, G, and B images. Nope.

Curiously, there's another double in the image, near the top-right. That's STI 2502! According to SkyTools 4, this is a pair of stars, mags 11.0 and 12.3, PA 71°, sep 15.1".

That's a good reference: STI 2505 should be similar. A bit tighter and more upright...

Conclusion: B star not visible. Missing. No obvious alternate candidates in the region. Is B a long-period variable star? Did the star quietly end? Did J. Stein goof up on the coordinates?


I wondered at all the streaks in the image. Satellites? But they show in the R, G, and B images in the same location. Sensor problems.

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