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Re: downloading data



On Wed, 28 Sep 2005 10:42:32 -0400, Michael Richmond
<richmond@stupendous.cis.rit.edu> wrote:

>  Andrew wrote:
>
>> One degree boxes now mean Sec(Declination) degrees in
>> RA so my boxes now overlap except on the equator. Just
>> another minor change to my code to ignore the stuff I have
>> read twice.
>
>  I'm the guilty party who asked Michael S. to make this
>change.  Most of the other tools I use to request data
>from big databases (SIMBAD, NED, etc.) use the convention
>that a one-degree box cover a square one-degree region
>on the sky.  The old TASS interface yielded a square
>region near the equator, but an increasingly elongated
>rectangle as one moved towards the poles.  I think
>that the new convention will make analysis simpler for
>most users.

Yes. I now see that my code was horribly lazy and
needed fixing up to deal with edge effects and working
away from the equator.

>
>> But some things have not changed. One is still given the
>> incorrect error estimates:
>
>  I'm guilty of not moving quickly on this point.  I have
>been wanting for a long time to provide two tables of
>information:
>
>     1) table of scatter of Mark IV database magnitudes from 
>             their mean value, as function of magnitude,
>             something like this (I'm making up values here)
>
>                 V mag         7       8      9     10    ....
>                 V uncert    0.03    0.05    0.07  0.10   ....

Well - that's an omnibus first guess but it throws away the
information about variable sky brightness and variable
aperture size.

Or has this information already been thrown away? I see
that in another post Tom is talking about reprocessing
raw CDs; this would be quite unnecessary if the subtracted
mean sky brightness and aperture size were recorded
somewhere. If these data have been thrown away, then
we are out of luck for the quick fix.

>...

>  Andrew, would these two tables, and a single "typical" uncertainty
>value based on them, satisfy some or all of your needs?

Without the mean sky brightness and aperture for the
image, I can do about as well by adding one line to my
code to compute Magerr(Mag) instead accepting the
value read in. 
>
>                                          Michael

Andrew Bennett, Avondale Vineyard, NS, Canada