Hello Lawrence,

these big yellow squares are nebulae. If you zoom in enough for some
of the larger / brighter ones there are isophotes too. Normally the
appearance change between zoom level 4 and 5, the same as for the
milkyway isophotes. Some of the nebulae are IC and NGC objects, so
they don't disappear when switching off nebulae (these are mostly
objects from the LBN [Lynd's Bright Nebulae], vdB [van den Bergh]
and Sh [Sharpless] catalogs).

> >One thing I have noticed (and which I mention in case it aids
> >diagnosis) is that the isotopes toggle does do something: If I go to
> >(for example) M42 at level 6, it toggles a few nebulae (yellow squares)
> >on and off -- their labels stay there and the squares toggle off as
> >isophotes toggle on, and vice versa. (e.g. LBN 956; S 278).

For me these big yellow squares are very important. They give the
outermost extents of the nebulae entrys of the catalogs mentioned
above. And there normally no shape is given, only a diameter. So
what to do if you want to display these nebulae in Guide? Take a
square or perhaps a circle. And Bill decided to use a square.
By the way, most of these nebulae are very dim (even
photographically) so if you aren't interested in doing deep sky
photography with large fields (most of these nebulae are huge, several
degrees in diameter [Orion, Cygnus or Scorpius comple]) you can
turn them off.

> No, but I want to add a bit here. Those big yellow squares are a
> nuisance to me but I cannot get rid of them. The isophotes switch has
> *no* effect on them on my computer, but some of them go off if I switch
> off nebulae. I don't *want* to switch off nebulae! I don't understand
> what they are meant to do, because I cannot see the point of having big
> yellow squares all over the sky. I *did* once manage to switch them
> off, but successive versions of Guide do not keep the same settings, so
> I forgot all over again.

Hope this helps.
Clear skies
Bernd


Bernd Brinkmann
Herne, Germany

http://homepage.ruhr-uni-bochum.de/Bernd.A.Brinkmann/index.html