[Prev][Next][Index][Thread]
(meteorobs) Telescopic Charts on the Web (was NAMN LM Charts)
Thanks for the comments Gary and Sirko.
I chose GIF because I thought it was widely used on the Web already,
and therefore could be downloaded and printed by the majority of the
readers. It affords a quick look unlike compressed PS. Also I could
produce a pipe which could convert the PostScript files to GIF using
Ghostscript and pbmplus. The pixel geometry is adjustable. So my
experiment was to increase the resolution whilst retaining the correct
aspect ratio.
Given that it's white with the odd black circle I'd expect the size to
increase approximately linearly rather than quadratically. In fact it
goes more like root(magnification). However, if you give it too many
pixels, the image cannot be displayed on the screen. This is the
limitation of pixel-based formats. When I tried to display a 1836 x
2376 GIF, xv dithered it. At 918 x 1188 it comes out on the screen
and printer OK. Using xv the image quality is poor. Some solid lines
are dotted or absent. It would certainly be worth placing one or two
test charts online and ask interested meteorobs readers to print them
and see if they look acceptable. This must be sensible given that
there are a few sets of 164 charts for different instruments. No! I'm
not proposing to make them all available. Only charts needed for
specific showers in Telescopic Observer Notes similar to those which
used to appear in WGN will be available. Even then that's tens of
charts. There's also the complication of US paper sizes...
PS gives high quality. However, it was too bulky as Lew will testify.
Compressed PS didn't save that much, though I only tried UNIX compress
and not gzip or ZIP (I'm on a UNIX workstation). Even though PS is
widely used by professional astronomers, I want the telescopic charts
to be available to any (amateur) meteor observer.
Malcolm
References: