Hi folks,
Some comments on "missing variables" (and variable display in general),
Epsilon Lyrae (and display of binaries in general), low-precision lunar
positions, and asteroid symbols:
MISSING VARIABLES:
Roger, about the missing TT Gem: this star is marked in the GCVS
as being of type 'CST', 'Constant', i.e., somebody thought this was
a variable and then changed his/her mind. Z Gem is another case of this.
You can get Guide to display such stars by editing VAR_TYPE.DAT and
changing the lines
CST xP Formerly thought ^variable^; further observation didn't
CST xP confirm this.
to read
CST 9P Formerly thought ^variable^; further observation didn't
CST 9P confirm this.
(As you might expect, further playing with VAR_TYPE can be done
to set which variable types are shown, their colors, and whether
they are shown at maximum or minimum magnitude or somewhere in between.
For details, look at the file \compress\var_type.doc on the Guide CD.)
EPSILON LYRAE:
Ben, about Epsilon Lyrae: you're right, there is a problem
here. Tycho-2 does describe this as two stars, TYC 3122 3439 1 and
TYC 3122 3439 2. They have different magnitudes, but unfortunately
the same position. I could put in an ugly and inelegant hack to handle
this situation and shift one a bit relative to the other. But the Guide
8 CD has the "Fifth Catalog of Orbits of Visual Binary Stars", and it
is quite possible to link this in to Guide so that orbiting binaries
are shown in the Right Manner. (At present, even if both components
are shown, they don't orbit one another. Animate, for example,
Alpha1 and Alpha2 Centauri, and instead of going around one another
every eighty years or so, they pull apart and go their separate ways
in straight lines.)
LUNAR ALGORITHMS:
Paul, thanks for the offer of the low-precision lunar code. I
actually have that method implemented in Guide, and the C source
code is part of the "basic astronomical functions" listed at
http://www.projectpluto.com/source.htm#astrocalc
This method was used in early versions of Guide, and is still
used when you select "low precision".
Great minds are thinking alike, though; doing a low-accuracy
test to see if an event is at all possible, followed by a high-accuracy
computation to make sure it actually occurred, is something I expect
to do. It ought to give me a substantial improvement in speed.
ASTEROID SYMBOLS:
Alan, about the large 'X' for asteroids: I did make some changes
here not long ago, so I'm not too surprised that it cropped up after
implementing the current version of Guide.
-- Bill