Hi Lawrence,

"...and Charon is (sadly) somewhat too slow for larger numbers of images."

Could you please send me an image or two, plus your charon.dat file?
Depending on its settings, Charon can be either quite fast (usually
a second or so per image) or insanely slow (minutes to hours per
image). My usual process to speed it up includes steps such as:

-- Take the measured focal length (reported by Charon when it
matches an image) and enter it in Charon's 'settings' menu. Then
set the "scale tolerance" in that same menu to be .01, meaning
that we expect at most a 1% variation in the image scale. That
sort of variation can happen due to temperature changes, shifting
mechanical parts, etc. If you instead leave a high scale tolerance,
Charon ends up checking a lot of "possible" matches that are, in
fact, not really possible at all.

-- Cut the "number of stars used" down to seven or ten. Charon
really needs only three, maybe four stars to do the initial match.
Set seven, and you can allow for the fact that, of the seven
brightest "stars" in the image, one is perhaps your target
asteroid, one may be a blob of noise, and one or two may
be real stars not listed in your catalog of choice.

(This last is especially a problem for SA2.0 users. That catalog
omits plenty of bright stars, requiring you to bump the "number
of stars" up to, say, 20 or 30, in hopes that four or five matches
can be obtained! And Charon's performance drops _very_ dramatically
with an increased "number of stars". This is why only a few truly
devoted citizens are using Charon with SA2.0.)

-- Charon will tell you the field size, in arcminutes, of your CCD
camera. Compare this to the "search distance" in Charon's
settings menu. Some people with (say) a 12' by 9' field of view
will set that search distance to 12', because they figure the
target object is going to be near the sides of the chip. In that
case, the 12' radius will cover the far corners of the chip.

Others who expect to have the target near the center, with
perhaps 2' of error, will make that search distance 8'. And so
on. Setting the search distance to be unnecessarily high will
cause Charon to load more comparison stars, so it'll be slower
than it has to be.

-- If you're using A2.0, you may have a lot of catalog stars
that are so faint they don't really appear on your image anyway.
(And if they _do_ appear, their signal/noise ratio in your image
is so poor that they really ought not to be counted anyway.)
Take a look at the "mag limit" field in the Setting menu, and
set it to a brighter value. This will omit the "problem" faint
stars, causing Charon to run faster and perhaps getting some
better fits.

-- Quite a few people have setups wherein the orientation of
the camera is constant... say, in every image, north is up and
east is left, or some variant of this. In such cases, you should
make use of the "max tilt angle" parameter near the end of the
Settings menu. This can really speed Charon up. If you know
ahead of time that the image is oriented to position angle 90,
plus or minus five degrees, then Charon can almost instantly
ignore 350 out of every 360 "possible matches".

Looks as if I've got something to cut and paste to the Charon
page, under a new "if Charon is slow" chapter...

-- Bill