Scope control, coordinate systems
Bill J Gray Oct 16 7:22 AM
Hi folks,
My apologies for the long delay in replying! I sent one reply
about instrumental magnitudes and the Magellan II and a few other
items, which apparently ended up in hyperspace. My thanks to those
who stepped in to answer these.
James Lummel asked, "...is it possible to have Guide automatically
follow the telescope as you move it around?" Yes. This is a very
recent and somewhat "in-testing" sort of feature. Go into the Toolbar
dialog, and at the end of the list of functions, you'll see a
"Toggle scope location indicator" item. Turn this one on, and
you'll have a new button on the toolbar (labelled, with no real
logic, "3"... I didn't add a new image, I recycled an existing one.)
Click on that button, and Guide will start "tracking" the telescope.
Click on it again, and it will stop doing so.
Ben, regarding positions for stars shown in Guide: as I wrote
previously, the "Go To... Star.. Common Name" function finds the
position of the star as of 1 January 2000, no proper motion added
(this will be fixed in the next update I post.) Guide sends
coordinates of date to the telescope, since that's what an LX-200
requires. (And, as Anthony Kroes pointed out, so do some other
scope control systems.) Be warned that unless your telescope has
_very_ good tracking, none of this makes any real difference!
At present, the difference between J2000 coordinates and those
"of date" is, at most, a few arcminutes. (A decade or so from
now, the difference will grow to a quarter degree or so, and
perhaps the manufacturers of these boxes will decide it's time
to account for it.)
It does sound as if perhaps Scope is expecting _everything_ to
be in J2000 coordinates. (Mel? Is this correct?) If so, you
can revise Guide to send/receive J2000 coordinates when doing
LX-200 scope control. Hit Alt-J and enter
SCOPE_EPOCH=2000
Quite a few people have built "home-brew" LX-200 clone systems,
and some have mentioned that their boxes really want J2000 coordinates,
not coordinates of date. So I added the above command so that both
systems could be supported.
-- Bill