[Kstars-devel] Some observations regarding USNO NOMAD in KStars

[Akarsh Simha]

Hi,

Here's a tarball containing a bunch of plots of the region around
trixel 12310. The x-axis is right ascension in hours and the y-axis is
declination in degrees.

http://www.ph.utexas.edu/~asimha/KStars-NOMAD-Tests.tar.bz2

Test 1: Shows that there are sizable differences between data dumps of
     	USNO NOMAD made with different criteria.

Test 2: Shows the effect of precession computed by KStars, between
     	J2000.0 and 2012.3

Test 3: The precessed coordinates of Test 2 were shifted by constant
     	RA and Dec shifts to make them coincide with the unprecessed
     	J2000.0 coordinates. Note the existence of spuriously
     	introduced precessed stars (green crosses that are not
     	coincident with a red plus). Note also the existence of
     	outliers that did not have precessed counterparts (red plusses
     	that are not coincident with green crosses). Note also that
     	these red outliers form a nearly right-angled triangle on the
     	top right of the image. Hmmm...

Test 4: The red outliers from the previous figure are all from Trixel
        12310 for some strange reason, and not the neighbouring trixel
        -- they all coincide with a blue asterisk from Trixel 12310.

Test 5: Note that some stars that were existant in trixel 12310 never
     	got JITUpdate()-ed despite making magnitude limits for trixel
     	12310 as high as 30 (red plusses without coinciding green
     	crosses). The reasons could be legitimate (i.e. some other
     	check failed; not checked yet). These could be the same stars
     	that were the red outliers in Test 3 (not checked).

Finally, attached is a diff containing the extremely ugly edits that I
used to do the debugging. I'm attaching them mostly for reference and
not so much for future re-use. They are applied against
29ef0d11f906963ce4d0d066df781b483a6a0ca0, which I will push into
master in a few minutes.

Regards
Akarsh
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