Paul Schlyter wrote:
In article .com,

It would have been easier to do this sone 20 years ago. when 70 Oph passed
through periastron.

In the 1980's I made some drawings of 70 Oph using a 4-inch refractor.
After only a few years the motion was easily seen visually - 70 Oph had
then moved through some 90 degrees in PA.

Now its movement is much slower.

True. Though having a telescope back in the 1980s that could resolve 70
Oph was something of a "dream" for me...

I would be content seeing just some movement either in separation or
PA, though the latter will now be tiny. The pair look set to continue
to widen through 2020 when apastron will be reached, with a whopping
max. separation of some 7.5 arc-secs.

The other component I'm tracking with this star is its proper motion.
With a near one full arc-second per year, it should become obvious in
just a few years.

AA
http://www.publishedauthors.net/aa_spaceagent/