Hi Alan,

There's a way of getting the grid spacing you're looking for,
but it may not be quite as helpful as you might like.

Edit the file 'strings.dat' in Notepad or the text editor of
your choice. Look down at line 50, and you'll see

20' 1m

Remembering that, at the celestial equator, 1m in RA is 15' in
actual angular distance, you change that line to read

12' 1.1333m

(17/15 = 1.1333m). Save the file, run Guide, and you'll see
those entries in the 'grids' menu. Select those radio buttons,
and you'll have grids spaced 17' in RA and 12' in dec... at the
equator.

Move away from the celestial equator, and the RA spacing will
be (17 * cos( declination)) arcminutes. One way around this would be
to look at the object in question, divide 1.13333m by the cosine
of its declination, and use that value instead.

All this would still leave you with the grids centered on 12'
intervals in dec and 17' in RA, and you might wish to lay out a
pattern centered on some other point. I'll toss out the following
possible interfaces for comments:

(1) You start editing a new overlay, and set up the CCD frame
the way you want it for the first image. Then you click some button
to tell Guide, "Add a CCD frame at the currently selected position
and angle to the overlay." Move the CCD frame to the next desired
location, and repeat.

(2) A special "show mosaic" tool: you center the CCD frame
_once_, then tell Guide: "Add a mosaic of frames extending
two frames to the left and right, two frames above, and three
frames below." Guide creates the corresponding 5x6 grid of
CCD frames. You'd also need to be able to specify, for example,
that the frames should have a 10% overlap.

The frames would still go into an overlay, so you could click
on each, change colors, add text, delete some that extended
into areas in which you weren't interested, and so on... all
of the currently-available overlay capabilities.

(1), at least, wouldn't be too difficult. (2) would be
quite a bit trickier, but still not impossible.

Oh, yes... quite independently of all this, the ability to
just tell Guide to make grids of an arbitrarily specified spacing
would be potentially useful. This one is suggested occasionally
by those attempting to make "Uranometria clones". The 1-degree
square (at the equator) grid spacing isn't available in Guide,
so they have to use the trick mentioned at the top of this post
to get a 4m spacing in RA.

-- Bill