Hi Larry,

> It seems to me your program MoonView might be modified for use as a
> "poor man's" blink comparator to match stellar fields photographed at
> different dates. It should also be useful in the present case to
> match DSS .fits files to various star charts...

(For those wondering what MoonView might be... it's a project for
viewing lunar images on which I started some years back, but didn't get
all that far:

http://home.gwi.net/~pluto/moonview/

Basic idea was that you load up a lunar image, usually a .jpg; then
click on two craters and select their names. Given that, the image is
roughly registered, other features get labelled, and you can get a
latitude/longitude readout and measure distances and so forth. Though
it helps a _lot_ to click on a few more craters, to make the registration
more accurate.)

Back in the bad old days, star images were indeed registered by asking
the user to click on a couple of stars and entering their coordinates.
Several packages now will take an image, a star catalog, and a rough
idea of the image size and RA/dec, and then match stars from the image
to stars in the catalog, all without human intervention. PinPoint,
Astrometrica, and Canopus all do this. (My own DOS software, Charon,
was -- I think -- the first to have this capability. There are still some
people using it, but it is kinda clunky to use.)

Somewhat amazingly to me, we also now have astrometry.net, which can
just take any random image and figure out where in the sky it was taken.
(They took an approach I considered, and rejected as probably being too
slow. Turns out, it's not. Guess I should have given it a try instead
of rejecting it out of hand!)

Anyway. One _can_ load DSS images into Charon, or the other programs
mentioned above, and thereby register them to background stars and
modify their FITS headers properly. But usually, one expects to be able
to just download a DSS image and have it pop up at the right scale,
in the right place, tilted the right way.

-- Bill