[Comm2011] test plate system using 9 pointings

[Jeffrey Bout]

If have redone the checks in RA for the upper 25% of the coadd and the
lower 25% of the coadd.
The overlaps differ only 0.5 arcsec.
Which is not strange: at these extremely low declinations the relative
rotation between two coadds positioned next to each other (I mean in
RA) is almost nothing.
To see this: just think about the circle lengths of the equator and
the circle 1 degree up in declination. The latter is only 0.001%
smaller in length (1 - cos (1 degree)).
So if you consider an arc of the equator of 1 degree: the
corresponding arc at 1 degree up in declination is only 0.001% or 0.5
arcsec smaller. I assume these arc length differences in some way
relate to the relative rotation of coadds positioned next to each
other, if you can follow me...

So, for multiple reasons, I'm looking forward to your first Hercules
observations, which are at higher declination.

And: perhaps it is a good idea to do quick observations of whatever at
-60 degrees or something? (although KIDS is not at these 'extreme'
declinations)
You can find plate system pointings in
http://www.astro.rug.nl/~bout/plate_kids_decimal.csv
...

Jeffrey



2011/6/14 Edwin A. Valentyn <valentyn at astro.rug.nl>:
> fine,
> but for overlap in RA direction, please be aware that at bottom of field
> overlap is less than at top. So please  also check at bottom.
> Edwin
>
> On 13-6-2011 11:42, Jeffrey Bout wrote:
>>
>> Hi all,
>>
>> I've been busy with checking the coadds overlap of the 9 pointings for
>> testing the plate_kids_decimal plate system.
>> In this figure
>>
>> http://www.astro.rug.nl/~bout/nine_pointings.png
>>
>> you can see the boundingboxes of sourcelists derived from the coadds.
>> the overlap between the coadds in RA is around 2.35 arcmin and in DEC
>> around 7.45 arcmin. The figure already shows that there is little
>> variation in these numbers.
>> Whether these overlaps are enough depends on the dither strategy. Each
>> coadd has 5 dithers with 1.7 arcmin variation in RA and 5.7 arcmin
>> variation in DEC. These number are smaller than the overlaps between
>> overlaps, so when coadds are combined to some supercoadds, no areas
>> with less coverage will appear in the coadd-overlaps.
>> So I conclude that at low declination the overlap between coadds
>> following the plate_kids_decimal is enough.
>>
>> PS: Here a detailplot of RA overlap between coadds with sources (+ and
>> x of 2 coadds).
>> http://www.astro.rug.nl/~bout/nine_pointings_detail.png
>>
>> Jeffrey
>> _______________________________________________
>> Comm2011 mailing list
>> Comm2011 at astro-wise.org
>> http://listman.astro-wise.org/mailman/listinfo/comm2011
>
> --
> -------------------------------------------------------------------------
> Prof. Dr. Edwin A. Valentijn       University of Groningen
> Coordinator Target                 www   : www.rug.nl/target
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