Alpha Crucis - Acrux - Double or Not

[Davekyn]

Hi, what really defines a double star?
http://www.youtube.com/watch?v=1L4Rre7v8a0

Are many doubles, gravitationally bound?

Is there a good resource about that can give me the distances between doubles.

I am more interested in doubles that are very close to each other and would love to find information on those targets.

I guess when viewing clusters as well...it would be good to know just how far these stars are from each other, as opposed to just enjoying the patterns in which we see them.

Having trouble getting the information, to keep me motivated. What other factors do you consider when gazing upon such targets...Spectral/color....???

[Davekyn]

OK...found additional info in the drop down box at the link I provided. It's just that I found words like Visual Double or Optical Double which confused me to weather or not, its a double or not...like its just another star that is eighter bigger, smaller, brighter, dimmer, in front of or behind.

I'm thinking of doing some more visuals on doubles and just fishing around on the topic is all. I really have no idea!

[GeoffW1]

Hi David,

The definitive resource on multiple stars (some have 3 or 4 components) is probably the Washington Double Star catalogue

http://ad.usno.navy.mil/wds/

You will need to have a good read of the notes and format explanation first, and know the RA of the object you are after, but it is very complete in detail.

For a more usable source I like the Eagle Creek list, although it is a bit garish :)

http://astronomy.eaglecreekobservatory.org/doubles/

It is indexed by constellation, and the product of 2 years work by Kevin Muenzler, who has been kind enough to give IIS a copyright release to use bits of it internally, as long as we credit him. These lists link to the Simbad cross-reference site

http://simbad.u-strasbg.fr/simbad/

where you can link an object in other catalogues such as the SAO catalogue

http://tdc-www.harvard.edu/catalogs/sao.html

which is not specifically about multiple stars, but it is implemented in some go-to systems eg Synscan and Meade Autostar.

Cheers

[Davekyn]

Just what I needed...Excellent start for me!
Thanks Geoff