Double stars: Where’s the secondary?

[DEnc]

I’ve downloaded the WDS catalog of double stars and filtered on systems that might show orbital displacements detectable in the time frame of a few years. But how to identify the secondary?—The entries in WDS have coordinates for the primary star, but not the secondary. However, the distance between them and the angle are listed (rho and theta), so I dusted off very dim memories of trigonometry, applied them to this problem, and they seem to be delivering! I’m amazed, not by the foundational math itself, but by its “idiot-proofness”.

Here are results for STE 16. The expected coordinates of the secondary were calculated from the 2015 catalog values for the coordinates of the primary, and by rho and theta. The software MPO was used to generate a chart and to identify a candidate secondary star falling very near the calculated coordinates.

A measurement of rho and theta with my data are in the ball park of the catalog values. But the difference is intriguing--only time will tell if the discrepancy in the observed rho versus expected rho are due to the movement of the secondary in the five years between the catalogued value and my observation.

I’ll apply this to the few dozen other systems I extracted from WDS, and see if there are measurable changes over the months and years.

It seems almost miraculous to me that talented people have developed consumer software enabling amateurs to explore these sorts of things. What a wonderful time to be pointing a telescope up!

SV110ED 4” achromatic refractor
SBIG STT-8300M CCD camera
JC-V filter
MPO software

[Graeme1858]

It will be interesting to see what you actually observe as compared to the calculations.

A wonderful time for astronomy indeed!

Regards

Graeme