Re: mark iv compression

[Tom Droege <droege@wwa.com>]

Herb,

As our compression expert, why not try compression with Data Disk 15 which 
you also have.  Try it and see what is lost and report back.

Below, I don't think that I said I was not keeping the raw data.  I am.  It 
is just that I am keeping it after the RawToFits translation which puts it 
into .fts format.

Tom Droege

At 03:46 PM 6/7/00 -0400, you wrote:
>On Tue, 06 Jun 2000 17:16:23 -0700, Chris Albertson 
><calbertson@logicon.com> wrote:
>*>
>*>One thing I thought of that I'll ssuggest we concider:  I seems that we all
>*>want to keep the raw image data, Tom is keeping it just as it came off
>*>the camera and Arne has suggested after 10X compression.  After reading
>*>Jures tech note I thinkg we should at least modify the header to include
>*>corrected WCS (ra, dec, image scale and rotation and maybe more) before
>*>the data is archived.
>*>>
>*>  Chris Albertson
>
>Some of you may recall I have a Tech Note on compression, written before
>Mark IV data was available. While I've updated the references in it,
>I have a bit more information to include which I will add shortly.
>
>I've reviewed our recent correspondence on compression: I don't see offhand
>any references to compression tests with current Mark IV data. I may have 
>missed
>something, I'd appreciate any info sent to me so I can add it to my
>Tech Note. (My review was cursory, no offense if I missed some recent work.)
>
>But my impression is that NOW is the time to test the "new"
>uncoma-ed Mark IV image data for compressibility, if one or more sets
>of reduction tools and/or programs are available for A - B testing.
>That is, results from compressed vs. noncompressed images. The Tech
>Note I believe will suggest the kinds of testing done previously on Mark III.
>While it suggests methods, I would expect different results.
>
>Tom's recent suggestion was *not* to keep the entire image, but to keep
>the pixels measured ONLY. In effect, compressing the image "array" to only
>those components which contribute to starlists, if I read his suggestion
>correctly. One could do the arithmetic, but I would guess that would be
>on the order of 10:1 compression. That too should be tested.
>
>By the way, the local computer superstores have recently offered 20GB
>or 30GB hard drives for $99. I will again suggest the least effort
>kind of "archiving" may well be to fill up one of these drives and to
>put it on the shelf, perhaps with a $10 '486 computer wrapped around it.
>There will be no shortage of large, cheap hard drives and cheaper, previous-
>generation computers.
>
>Herb Johnson
>
>Herbert R. Johnson              http://pluto.njcc.com/~hjohnson
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