Every star you see tonight is showing you old light - some of it as old as you are.
Light LeftFind the star whose light left the year you were born
A star 36 light-years away shows you light that set out 36 years ago. Add the people for a card and the page finds each of them a real naked-eye star whose light arriving now left it around their birth month - with the measured error bar, an honest tag when the match is only close, and when and where to look. Then it joins their stars into one constellation on an atlas plate.
Try a sample:
1 Who is on the card
2 The star plate free
Swipe the plate and the ruler sideways to see the whole sky.
The light ruler
3 The card's words
One run reads the list, your note and the page's matches, and writes the card: a title, a headline, a caption and a finding line for each person, a footnote and a line to read under the sky. It gives one verdict, checked in this order: true light if every person's star is on the year; mostly true if at least half are; otherwise stand-ins. The stars are matched by the page, not by the run.
Pricing as soon as the session is ready...
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How the page matches a star
Light travels one light-year in a year, so a star's distance in light-years is how long ago the light you see tonight left it. The page holds 374 stars brighter than about magnitude 5.6 out to about 108 light-years, with distances from their Hipparcos parallaxes (the 2007 new reduction) and the error each measurement carries. A match is on the year when a person's age falls inside the star's error bar, or within half a year of its distance; near when it is off by up to about two years more; a stand-in when nothing closer exists - there are no naked-eye stars between about 12 and 16 light-years, for example. Anyone younger than the nearest star's light (about 4.3 years) gets still on its way, with the month that light arrives.
Among the matches the page prefers stars that rise well from your latitude, then named stars, then brighter ones; you can pick another from each person's list. The evening month is when the star stands highest at about 9 pm and is approximate (time zones and summer time shift it by a couple of weeks); heights are at that moment, in degrees and in fists held at arm's length. Nobody can buy or name a star - this card only follows the light.