Tuesday, August 29, 2006


Absolutely brilliant!

I've been thinking that I need to take the web pages I encounter (like the one at SEDS) documenting double and multiple stars with a grain of salt.

Not having a formal catalogue of double stars, possibly in trouble with the public library, I am left with searching online.

At the same time, I've had this feeling that this kind of information must be available online from "official" and trustworthy sources.

And after a couple of hours working in the Bright Star Catalog (bsc5p), examining the complete table of 9000+ stars, getting to know the system, the query language, sorting features, means of output, I can say that I am astounded with The High Energy Astrophysics Science Archive Research Center (HEASARC) archives at NASA's Goddard Space Flight Centre!

I used the following criteria:

alt_name != "" AND
dec > -50 AND
vmag <> 10 AND
m_sep > 10 AND
m_sep = 0

so to exclude unnamed and unnumbered stars in a constellation; avoid candidates only visible in the southern hemisphere; include stars viewed, relatively easily, in either a 8" or 6" telescope in fairly dark skies; that are not too close together.

The final m_sep = 0 is to extract a handful of other proximal stars like Mizar.

I selected the following fields for output:

name, alt_name, ra, dec, vmag, ads, fk5, hd, m_cnt, m_mdiff, m_sep, sao, spect_type

  • name = an HR / Yale number
  • alt_name = Alternate Name (usually Bayer and/or Flamsteed), e.g. "79Zet UMa"
  • ra = Right Ascension, J2000
  • dec = Declination, J2000
  • vmag = Photographic Magnitude
  • ads = Aitken Double Star Catalog Designation
  • fk5 = FK5 Star Number
  • hd = Henry Draper Catalog Number
  • m_cnt = Number of Components in Multiple System
  • m_mdiff = Magnitude Difference of Double or the Brightest in Multiple System
  • m_sep = Separation of Components of Double or the Brightest in Multiple System
  • sao = Smithsonian Astrophysical Observatory Catalog Number
  • spect_type = Spectral Type of Source
I requested an ascending sort by m_sep.

And finally, I told the system to produce Excel compatible results. Which, after a moment, appeared in my OpenOffice Calc spreadsheet program as a 3D worksheet file! Wow!

Oh, dear. Over 700 multiple stars to check out! ;-)

At least now I know that I have an official list. No doubt.

Where I can see this being very useful is the day before a planned observing session. I can conjure some criteria to make a nice short list of a few targets, perhaps just the doubles within one constellation.

No comments: