Hi Bernd,

> Another classification could be the wavelength of catalogs (e.g radio
> sources) or plate boundaries of catalog "pages".

True; and there is also a class of "shorter than visual datasets"
(gamma ray bursters, for example).

> I think that users who wants there own photgraphic horizon should be
> able to create a panorama picture beforehand with 3rd party (free)
> software. Then you have to get the information of the orientation
> (eg. where is north, pixel column x) and where is the mathematical
> horizon (zenith distance 90 deg, pixel row y). Then your task
> (that of Guide) would be to transform the image pixels to the
> screen pixels of the Guide window.

It occurred to me, after I replied, that somebody must have made
some decent panorama-stitching software out there. It looks as if
Hugin (http://hugin.sourceforge.net/) is well thought of.

Doing what you describe would definitely be easier than requiring
the user to do the photographic horizon all within Guide (both for
me _and_ the user). The "placement" would consist, I think, almost
entirely of providing a way to rotate the horizon in azimuth, and to
raise/lower and rescale it in altitude.

If anyone has produced such a panorama and is willing to have it
appear in Guide 9, please let me know. I absolutely do not intend to
attempt to get this working in Guide 9 when it ships. But if the
image files are on the DVD, then a future update on the Web site
might include the ability to use those image files. I'd like to
have at least a few examples on the DVD.

> One more thing is the priority of drawing. For example shouldn't
> the panorama be visible in the legend area. What's with objects
> (stars, planets and so on) below the horizon line? Should they be drawn?

Yup. Those issues also appeared when Guide started to show a filled-in
ground and objects around the horizon. In reality, you can't see through
the ground or objects on the horizon (unless you are imaging with
neutrinos), but Guide makes those objects transparent by default.

If you hit Alt-J and enter

GROUND_DRAWING=2

then the ground and horizon objects become "realistic", and you can't
see objects below the horizon or behind trees. This may be realistic,
but reality can be annoying. Hit Alt-J again and enter

GROUND_DRAWING=

and the earth will again be transparent.

-- Bill