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On Fri, 23 Oct 1998 14:26:42 -0700, Chris Albertson <email@example.com> wrote:
*>No, FITS is a plain n dimensional array. In the FITS user guide
*>is a reference to a _proposed_ compression standard.(Warnock et al)..
As Arne says, there is no FITS standard.
*>Didn't someone here on this list look into compression and it's
*>effect of photometry? I'm sure I saw it written up complete
*>with some plots.
It was well discussed.
*>Delta encoding works OK for images (After whacking off
*>the noisy low order bits) but it does not take advantage of the
*>2 (or more) dimensional-ness of the data.
That is certainly true. Compression schemes that "match" the data to
be compressed do better. Schemes that produce "acceptable" data loss
do better still.
*>I don't think this is a big deal. Currently you can keep _all_ the
*>raw MkIV data at a pretty low cost on tape or CD.
As previously discussed, a night's viewing on Mark III will fit on ONE CD-ROM:
but Mark IV's proposed night's data may not. There was no consensus on tape
in our discussion; the consensus was that CD-ROM was a very convenient
medium that did not suffer from incompatibilities as did tape. I don't
care to reopen that discussion as I have nothing to add to it: but
I did want to introduce the notion to (eventually) establish the
dynamic range (i.e. reliable number of bits) from the Mark IV.
Herbert R. Johnson http://pluto.njcc.com/~hjohnson
firstname.lastname@example.org voice 609-771-1503, New Jersey USA
amateur astronomer and astro-tour guide
classic S-100 computers restoration & parts as "Dr. S-100"
rebuilder/reseller of classic Macs for your computing pleasure
and senior engineer at Astro Imaging Systems