Images

[Tass Mailing List <tass@mail.alembic.net>]

Date: Tue, 02 Jan 2007 16:50:46 -0600
From: Thomas F. Droege <droege@fastmail.fm>
To: tass@tass-survey.org
Subject: Images

Looking around, I estimate that I have images on 2000 CDs and 200 DVDs.
Best guess is about 500,000 images.  I would like to get them in a form
where images containing a particular star could be found.  This is
important if one tries to use the measurements, since funny things can
happen to a particular image.  An example is a faint satellite trail
that crosses a star image.  If faint enough, the data reduction does
not reject the measurement.  Both V and I images then look somewhat
brighter, simulating some sort of outburst.  To check this one really
needs to look at images.  There is probably too much data to be put up
on a data base.

I propose to start cataloging the image disks.  This is a good mindless
project for a sick person.  Just set up a system and start feeding all
the disks through it.  I would propose a small program that would do the
following:

1) Read all the fits headers on the disk.
2) For each write a summary line.
3) Output a file with the name tass_images_n where n is a sequential
number for each disk. The file would contain a summary line for each
image pair.  Note that we only have image pairs and we always have image
pairs.
4) I would then go through all the CDs/DVDs and generate the summary
files.
5) I would then label each CD/DVD with it's sequential disk number and
store them away in 50 disk cake boxes.

It would then be relatively easy to query the summary line file for say
all the images containing a particular star.  This is not perfect since
we only have the approximate center of each image stored in the fits
header.  One could then extract disks 10,457, 2068 relatively easily
from the stack of cake boxes.

I am willing to read all the disks and set up the cake box stack.  I am
also willing to answer a reasonable number of queries by manual
extraction of the images.  If this gets to be a burden, then we have a
good thing - the data is interesting - and one could go to the trouble
of loading all the images in some data base.

At the moment, we can't even find a single image set spanning the
northern sky.  This might be useful and could be easily constructed once
we had the summary line file.

First we need to agree on what should go in the summary lines.  Some
things:
1)Disk Number
2)Image Name
3)ra of image center
4)dec of image center
5)JD t1ime of exposure
6)exposure length (we have 100 and 200 second exposures)
What else?

Then I would need a program to do this.  Any volunteers?  Does not seem
like a big task for some of you.

Tom Droege

-- 
  Thomas F. Droege
  droege@fastmail.fm