SCOPE COMMANDS:
Hi Mel,
I can certainly add such commands... though I'd prefer to stay away
from base 60-style "DD*MM"; ancient Babylonians may have had thirty
fingers on each hand, but I do not. Something along the lines of
#:Tr +DDD.DDDD#
#:Td +DDD.DDDD#
per minute ought to do the trick. (Low-earth objects rarely move
faster than 100 degrees/minute, but it can happen... and besides,
suppose somebody wants to track passing airplanes?)
I went to .0001-degree (about 1/3 arcsecond) precision because I know
some people image faint near-earth asteroids with the scope tracking the
asteroid. That causes the stars to trail, of course, but the fact that
it makes the asteroid easier to measure makes it worthwhile. So the
ability to specify tracking rates precisely could matter.
While we're about it, I'd like to add the following command:
#:Tf +DDD.DDDD#
...to set the rate of motion of the 'third motor' for field rotation.
Also, I suspect that a simple rate of motion will not be sufficient for
satellites. There is apt to be acceleration on time scales of _much_ less
than a minute. (Especially if the user selects an object about to pass
through a celestial pole on an equatorial, or through the zenith on an
alt/az scope... but even in general, if you take two satellite positions
a second or so apart and extrapolate a minute ahead, based on constant
rates in RA and dec, you'll have troubles.) So the following commands
would be nice:
#:Tr2 +DDD.DDDD#
#:Td2 +DDD.DDDD#
#:Tf2 +DDD.DDDD#
#:Tr3 +DDD.DDDD#
#:Td3 +DDD.DDDD#
#:Tf3 +DDD.DDDD#
These give half the acceleration and 1/6 the dacceleration/dt on each
axis. You might ignore them for the moment, paying attention only to Tr
and Td. But someday, it may help to know that:
RA = RA0 + Tr * delta_t + Tr2 * delta_t^2 + Tr3 * delta_t^3
Any other commands that would be useful? I don't think Meade will be
adopting any of these improvements, so we can basically do whatever we like.
Theoretically, we could do as Markus has suggested on this list: just
send the position at a high frequency. But including rate data could make
that 'frequency' lower and maybe allow for smoother tracking. Also
theoretically, if the update rate is user-settable, people can set whatever
update frequency works best with their scope... there is no need for that
to be 'hard-wired' in the code.
Users of 'real' Meade LX200s, with the limited command set, would tell
Guide not to send rate data and to update twice a second. Others could
do whatever their scopes can handle.
SBIG IMAGES IN CHARON:
I owe Octavi an apology. It turns out that ST8 support in Charon has
been broken for a while now. I found this out, in part, because an ST9
user e-mailed me about a problem loading images from his new camera. In
the process of fixing this, I found the ST8 problem.
It's been fixed, and there is now a CHARON.ZIP on the Web site that
ought to get you up and running.
NEW TEST VERSION OF GUIDE:
I'm about ready to post yet another update to the software on the Web
site. Adventurous persons should look here:
http://www.projectpluto.com/new.htm
for information and a beta version.
-- Bill