[vsnet-chat 1294] Re: Image Archieve

[Taichi Kato <tkato>]

[vsnet-chat 1280]:
> I've been doing SNe hunting for about six months using a fully
> automated  30cm (12 inch) Meade LX200 with a KAF-1600 based CCD =
> being controlled by a self written program.  The equipment will =
> produce about 200 images per  night.  With flat and dark frames, =
> that is about 175 megabytes  of data per run.  I'd like to =
> solicit the comments of the more experienced observers about =
> how long these images should be kept. I'm accumulating a =
> reference images for each of the galaxies in my observing list. =
> Obviously,  these reference images should be kept indefinitely.  =
> I've been deleting image files that are more than six weeks old.
> I get many  images that are defective in some way because of
> clouds, wind vibrations, etc.

   As for the Ouda case, we have (in principle) kept all images in CD-Rs
and MOs.  The data production rate at maximum is close to Steve's case.
In the very beginning of my career in time-resolved photometry of superhumps,
when the recording media were expensive, I was urged to delete image files
after obtaining the light curve: the data production rate by 10-sec
sequential exposures was probably astonishing to the observatory staff,
and the whole images were not (naturally) considered useful outside the
target and comparison stars.  I indeed once deleted images, but the policy
was changed soon after the media became less expensive.  As computers become
faster, it has become more and more easier to reanalyze (often automatically)
older images; it's not infrequent to make some excursions to old (already
once analyzed) images when new information becomes (e.g. new astrometry)
available.  I strongly recommend to keep images as long as possible.

   We were asked on the occasion of SN 1993J whether we had a previous
CCD image of M81, but there was unfortunately none.

Regards,
Taichi Kato

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