Re: how can you tell how far away stars are from the H-R diagrm

Dear Vince,
You can't tell how far stars are away by examining an H-R diagram because it uses absolute luminosities. [But if you know a star's apparent luminosity and where it falls on an H-R diagram, you can figure out its distance by comparing its apparent and absolute luminosities - mod.]

However, one of the blessing of these modern times is that all, I mean every bit, of astrometric data collected on the ground and from space observatories is available on the internet at http://adc.gsfc.nasa.gov/adc/quick_ref/ref_stellar.html. You may find it easier to use the amateur astronomy site set up by the Astronomical Data Center: http://adc.gsfc.nasa.gov/adc/adc_amateurs.html.

Jim Foerch
James C. Veen Observatory
Lowell, Michigan
USA