Re: V image fainter than I

[droege@snapmail.us]

Andrew and all,

There is a parameter in the sky.param file that sets the minimum sigma for
the star to be "found".  This was set at 3.8 for V and 4.2 for I for the
last run.  I could decrease the value for vsig to a low value for the V
image.  This could just be experimentally determined so that V stars began
to match I stars.  Michael had both of these set at 5 in the original
code.  I lowered the values because I thought that the two filter
requirement got rid of most of the noise detections.

Tom Droege

> On Sat, 19 Mar 2005 13:01:49 -0600 (CST), droege@snapmail.us wrote:
>
>>Paul and all,
>>
>>The current coded scheme is that we must have both a V and an I detection
>>to keep the measurement.
>
> A scheme I tried once while playing around was
>
> 1) Add reliably detected stars, V or I, to a finding list.
> 2) Process a new image in the regular way, fit
> precise astrometry etc & match to the finding list.
> 3) Reprocess for the unmatched stars in the
> finding list at the now known X1,X2 coordinates.
> Even for relatively faint stars, positions are ususally
> good to a small fraction of a pixel so one knows
> just where to look.
>
> Never got the bugs worked out, but it was "almost
> working" ...
>
> Has the merit of giving an estimate for Miras that
> have gone off the end in V-band.
>
> So my opinion is not to change a thing with the
> hardware or the way the survey is done: just
> fix the software.
>
> Andrew Bennett, Avondale Vineyard, NS, Canada
>
>