Over the last few months I've received several questions, so it's probably a good time to write a FAQ about StarMap.
Q: Who wrote StarMap, and how was it set up?
A: StarMap was written by Bob Donahue of the Center for
Astrophysics (and Mount Wilson Observatory) in order to
provide some sort of WWW/online service for amateur
and backyard astronomy enthusiasts. It is written
in FORTRAN and linked to a customized version of the
MONGO graphics library.
Q: Can I get a copy of the source code?
A: Not at this time. Since the graphics library is an
unofficial patch, it wouldn't do much good. Most
of the astronomy-related routines come from the book
"Astronomical Formulæ for Calculators" by J. Meeus
(ISBN 0-943396-01-8).
Q: I can't get the form to work properly!
A: This would depend your site's OS/platform and what Web browser
you are using. I do know that
Netscape
has the least problems, so you should look into
getting it.
Q: I get the file back, but I don't have a way to view it...
A: You need a PostScript previewer (like GhostScript). Check
the more popular FTP sites for whatever platform you are using.
Q: Sometimes the PostScript files come back with errors - why?
A: I'm not sure - this didn't happen with the testbed I set up
while debugging the program. It appears to be related to
the transmission of the file and not its creation.
I'm still trying to track it down and fix it.
Usually, running the form again gives a printable file.
Q: The PostScript files are SO LONG!
A: Yeah - the PostScript driver for MONGO was hastily written.
I'm purusing other possibilities for a graphics package,
and if one of them works, I'll set it up as a future version
(this will also hopefully solve the "broken PostScript file"
problem).
Q: Can I get a GIF/JPEG/TIFF/XBM image instead of PostScript?
A: Yes, if you use a program that converts PostScript to your desired
format. PostScript was chosen for three reasons: 1) At 300 DPI
the resulting file printed out looks much better than
anything on a screen (which is typically something like 72 DPI);
2) The idea was to provide something people could then take
outside and use while looking at the sky - thus GIF/JPEG/etc.
isn't practical; 3) MONGO had this as an option for output
and it was more-or-less easy to set up. (MONGO also has a
very inefficient driver for PostScript! I'm researching
other options, and might make a switch at a later date.)
Q: My city isn't on the list of cities - how are they chosen?
A: For the most part, they are picked by looking at the statistics
of what longitude/latitude pairs are selected. In other cases,
cities were chosen to provide interesting examples (e.g., Quito
Ecuador). Every few weeks, I'll look at the distribution of
coordinates, see if there's enough interest in an area to put
in an entry and update the files.
I have an idea for a way to at least give the user a rough
idea of what his/her latitude and longitude is. I'm still
working out how to install it.
Q: Why is it in Universal Time (and what is UT anyway?)?
A: UT was chosen for two reasons. First it eliminates needing to
worry which geographical area was in which timezone, and what
to do with different areas going through Daylight Savings
Time (remember some countries in Europe are now on DST,
and in the US some parts *don't* go on DST - everyone keeping
up? :-)
So, to make it easier, all times are in universal
time (UT). UT is roughly defined as the time in
Greenwich, England. It's 5 hours ahead of Eastern Standard
Time (4 hours ahead of Eastern Daylight Time).
July 14, 1996: The new version of the StarMap Home Page
shows the current Universal Time above the box for UT. So,
a quick way to figure out the offset from your local time to
UT would be to compare the time it says when you load up the
form and the UT listed.
Q: Can I make copies of the map and distribute it to my
class/club/etc.?
A: YES! This would be wonderful. The only requirements
are that 1) the map cannot be sold or bundled in a package
that is sold, and 2) the URL and copyright notice MUST remain
with the map.
Q: I'd like to be able to zoom in on a particular
constellation or area of the sky - can I do this?
A: No - but fear not - that's a project I'm thinking of doing
when I get a chance! (I need a good complete atlas down
to, oh, V=14 - if anyone has a pointer to one let me know).
I'm also hoping to set up an online "observers" guide
with constellation charts, and some pictures from the
24" TIE telescope. But all these things takes time
to do them.
July 14, 1996: If there are one or two people out there
who are really interested in astronomy, and are experienced with
the night sky, already have an account with telnet capabilities,
know HTML and UNIX and want to help me out on setting up part of
an online guide to the stars (think something like an online
up-to-date Burnham's Celestial Handbook) let me know.
The HTML and UNIX experience are absolutely necessary!
Q: I'd like to see constellation names, boundaries, Messier
Objects, double star designations, etc. on the map...
A: This would clutter the map. I do intend to put some
of things options in, when I get a chance. The constellation
boundaries are a little bit of a problem since they are
defined along epoch 1875 parallels, and would have to be
precessed to the current epoch (so no straight lines!).
The names would have to find places where they didn't
intersect with stars, lines, etc. The Messier objects would
probably want SOME kind of on-map legend (again avoiding
stars and lines). As I solve some of the logistics for
doing this, I'll definitely add those options in.
July 14, 1996: I'm still looking for a source for Milky
Way boundaries to add that in. As usual, if someone knows of
a source for this data, please let me know
Q: The Galactic Equator seems a little off...
A: Oh, you noticed that too? :-) It's probably a
bug, but my forumlas for galactic coordinates seem OK.
Q: It'd be nice to have lists of constellations, bright stars,
etc., on the Services page to go with the StarMaps...
A: Yes - and it's also something I'd like to undertake when I
have the time. (See above plea for a volunteer or two.)
Q: I went out and didn't see all the moons even though StarMap
had them all there...
A: StarMap doesn't (yet) keep track of the Jovian shadow, so
moons in the shadow are still plotted. (Again, if you have
an algorithm and would like to share it....)
Q: How about phases of Venus or Mercury?
A: That would be neat - again I'll have to have the time and
figure out where to put it! (I suppose this could be
selected or set automagically swapping the Jupiter/Saturn panels
depending on which planets were "up"...)
Q: How about Sunset/sunrise and Moonset/moonrise?
A: On the list of things to get put in...
Q: How about Solar position?
A: On the list of things to be put in...