Hi folks,

A late reply about mosaicking: I've been pondering this idea,
and may want to generalize it as follows. Please realize that
this is in the nature of brainstorming; I'm coming up with an
ideal solution, one that will doubtless require some pruning!

With a mosaic, the scope is pointed at successive fields to
build up the mosaic. More generally, people just want to go
to a series of points. Those points may form a grid, or they
may be a series of target objects: asteroids, variable stars,
galaxies, etc. So what we may really want is a bit of an
expansion of Guide's "user object list" capability, to become
useful as a "points to aim the scope at" capability. This
dialog is tucked into the Overlays menu, and hasn't gotten
much use or improvement in a very long time. But it has the
advantage that much of the necessary code is already in place;
I don't have to start from scratch.

The improvements I'd envision are as follows:

Within the user object list, one could tell Guide to add an N
by M grid of objects, at spacing specified through the CCD Frame
dialog, with a specified amount of overlap (given in arcminutes,
say), centered on the current screen center. M * N user objects
would then be added to the list.

It might be possible to specify a "spiral search" order (start
in the middle and work your way out) versus "start at the upper
left, scan right, drop one row, scan left, drop one row,
scan right..." versus "start at upper left, scan down, move
over to the right one frame, scan up..." Dunno how important
that is to anyone, though. (Still more specialized would be
scanning along a line, useful in recovering an asteroid or comet.)

The user-added object dialog already provides the ability to
delete objects, so if you want the M * N grid minus a couple of
fields near the corners, you can delete those.

You can already have Guide show user objects on-screen, as a
user-added dataset. It wouldn't be too tough to have them shown
as CCD frame rectangles. (Or, for visual observers, as circles
showing the actual field of view.)

You may instead zip around the sky and add "objects" at the
places you want to image.

Once you've got your list, you could tell Guide to sort it to
minimize total slewing distance. This is the "travelling salesman
problem", usually expressed as: a salesman has to visit a series
of cities, passing through each only once, and you want to find
the minimum travel distance. Getting a perfect solution for more
than about twenty points is usually next to impossible, but I've
code that can usually get within a few percent of a perfect solution
without much trouble.

Visual observers of both "goto" and "non-goto" persuasion might
like this whole system. Even if you're using a Dob, this would
let you select the objects you want to view, see circles for each
on-screen, then go out and view them, one after the other, in
an optimized order. Having the slews automatically done would
be optional.

People have occasionally asked for multiple user object lists.
That would become much more important with these proposed changes.

Okay, I've blathered on enough. Any comments?

-- Bill