Guide's display speed

Bill J Gray Sep 20, 2002

Mark has summed this up nicely. I'd add only the following:

The biggest slowdown Guide experiences now is often in
asteroid display. If you turn asteroids off and see a sudden
improvement in display speed, you'll know this is the case
for you.

Asteroids were a slight problem in Guide 7, but Guide 8
displays far more asteroids. It uses assorted tricks to speed
up display by knowing, in advance, that most of the asteroids
can't possibly appear in the current field of view, or can't reach
the current limiting magnitude. But as you zoom in and the
limiting magnitude goes fainter, that ceases to be helpful,
and Guide ends up having to compute a hundred thousand
asteroids or so in search of the one or two that _might_
appear on-screen.

Planets and comets are much less of a problem, simply
because there aren't nearly as many to deal with.

Format conversion is, as Mark indicated, a _very_ small
part of the problem.

Most of the object datasets draw up very quickly, but there
are occasional large user-added datasets that are not sorted in
RA or declination order. In such cases, Guide has to read
the entire dataset to find which objects appear on-screen.

Drawing the deep-sky images can take a while, since they
need to be accessed, decompressed, then drawn stretched
and tilted to align properly with the screen. Drawing the features
on planets when zoomed in is particularly slow.

-- Bill