Zeta Bootis

[John]

Can anyone tell me the current separation of the close pair in this triple system ?

I looked long and hard with my 6" refractor this evening and got elongation of the ariey disks with just a suggestion of a "waist" ie: a compact "peanut" shape but no separation.

I strongly suspect that this is a sub-arc second pair at the moment - can anyone confirm that ?.

Thanks

I also tried Eta Corina Borealis and got more elongation but still no clear separation - my info has this pair around 1 arc second so I guess it's a real toughie for 6" ?.

I was using 343x and the Cromacor corrector. The scope was well collimated and cooled.

[lunator]

Hi Jon

I'll check the details out for you

Cheers

Ian

[perrin6]

I was looking at eta CrB last night with 13 inch and it looked really close at 200 X - closer than the 1 second given by the 'double star list ' site http://www.mapug-astronomy.net/AstroDesigns/MAPUG/DbleStar/DbleStar7.htm. Couldn't see any dark sky between them although my mirror's figure not great nor seeing conditions. Googling showed one figure as .5 arc seconds though cannot find date for this info and period seems to be 41.6 yrs so might be closer than that.

[brianb]

From the 2010 BAA Handbook:

Zeta Boo, 2010.0 PA 294.0 sep 0.53; 2011.0 PA 293.2 sep 0.50 (period 123y)

Eta CrB, 2010 PA 167.8 sep 0.60; 2011.0 PA 176.6 sep 0.63 (period 42y)

[Moonshane]

hi John

I also made a similar observation (I assumed that the separation was per the site I used The Constellations Web Page which states 0.9). http://stargazerslounge.com/observing-deep-sky/102362-observing-report-19th-april-2010-a.html

do you know what is the minimum split we can expect to be able to do for double stars?

cheers

Shane

[John]

Thanks for the feedback folks and thanks for the data on these objects Brian. Looks like I was doing pretty well even to see elongation with 6" of aperture. Porrima was very cleanly split last night and I believe thats around 1.4 - 1.5 arc seconds so at my location with this scope I'm gussing my limit for equal brightness binaries is probably going to be around just over an arc second.

The Dawes limit for the scope is .77 arc sec and the Rayleigh limit .93 arc sec so, taking into account less than optimum observing conditions and mass produced optics I think I'd be happy if I could split a 1.1 or 1.2 arc second double.

[lunator]

Hi John

Here is the info from the 6th orbit.

The separation will be around 0.52" so pretty good going

Theta Rho

2010

294.0 0.530

2011

293.2 0.501

[lunator]

The Eta CrB figures are, so it is probable about 0.64 at the mo.

2010

176.6 0.630

2011

184.7 0.658

[John]

Thanks Ian - I imagine that splitting these at the current time would be a challenge for even large scopes

[lunator]

John

The seing would have to be very good

I will have a try at these soon.

Cheers

Ian