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GSC and DS23
I have tried to match all the stars from DS23 with GSC
1 stars. 5.74% of the stars did not have a
counterpart within 1'. Below I give the number of
times (percentage) a distance to the closest GSC star
(in arc seconds) appears:
d" % d" % d" % d" %
0 27.89 1 23.88 2 14.30 3 10.04
4 7.20 5 5.33 6 3.68 7 2.53
8 1.61 9 1.02 10 0.53 11 0.28
12 0.16 13 0.08 14 0.04 15 0.02
16 0.02 17 0.01 18 0.01 19 0.01
20 0.01 21 0.01 22 0.01 23 0.01
24 0.00 25 0.00 26 0.01 27 0.00
28 0.01 29 0.00 30 0.01 31 0.01
32 0.02 33 0.02 34 0.02 35 0.02
36 0.02 37 0.02 38 0.02 39 0.03
40 0.03 41 0.04 42 0.03 43 0.05
44 0.04 45 0.05 46 0.04 47 0.05
48 0.05 49 0.06 50 0.05 51 0.05
52 0.07 53 0.07 54 0.07 55 0.07
56 0.07 57 0.08 58 0.08 59 0.09
This gives some idea of the accuracy of the photometry
of DS23 compared to GSC1 (I leave it up to the
specialists to find out what). At about 20" there are
practically no matches any more. For larger distances
the number of "matches" increases again, simply
because the coincidence to encounter another
(non-related) star will be higher the larger the
distance.
Would it be worthwhile to give the distribution per
declination zone, to look for systematic errors near
the edges of the frames ?
There are 277 objects, at least one night brighter
than mag 13, and observed at least twice, which do not
have a GSC counterpart within 20". Most of these do
have a match in the USNO-A2.0 catalog within 10" with
a star of comparable brightness, so these are probably
flaws in GSC 1. The remainder of the 277 objects can
be identified as the minor planets Zelinda and
Aquitania, the variable star V617 Mon, and 10 objects
for which there is a match in USNO and GSC2.2, but too
faint in my opinion. I give these below (TASS object
number, RA, Dec, JD, number of times observed on that
night, V, V-I, then a line with U and distance in
arcsec to USNO object, id, B, R,
and a similar line for GSC2.2, starting with G):
11590 92.3390 5.1276 2452251 3 12.95 0.48
U 7 0900-02390194 19.6 18.5
G 10 N220031214013 14.5 13.6
40550 101.4235 8.5482 2452287 8 12.81 1.20
40550 101.4237 8.5480 2452296 6 12.84 1.29
40550 101.4236 8.5476 2452312 5 12.74 1.20
40550 101.4236 8.5481 2452313 2 12.89 1.30
U 10 0975-03814473 18.2 16.5
G 9 N220302126014 18.0 16.7
40852 101.5150 8.1052 2452287 7 12.85 0.74
40852 101.5158 8.1052 2452296 12 12.86 0.69
40852 101.5156 8.1052 2452313 8 12.73 0.66
40852 101.5156 8.1054 2452312 10 12.88 0.79
U 3 0975-03828666 16.4 15.5
G 4 N220302112709 13.7 12.6
41675 101.7621 7.4209 2452296 1 12.98 0.47
41675 101.7620 7.4207 2452313 3 13.06 0.37
U 6 0900-03508338 17.9 15.8
G 6 N220111210294 18.3 15.4
43045 102.2028 7.4360 2452296 6 12.68 0.41
43045 102.2027 7.4355 2452312 7 12.70 0.41
43045 102.2024 7.4355 2452313 7 12.76 0.45
U 5 0900-03576418 15.5 14.3
G 5 N220111210990 15.3 14.2
43658 102.4086 8.5422 2452296 5 12.90 0.71
43658 102.4086 8.5426 2452312 7 12.88 0.65
43658 102.4079 8.5425 2452313 1 13.16 0.92
U 0 0975-03969512 18.9 18.1
G 3 N220113229681 19.4 17.9
47254 103.5355 8.4051 2452312 3 12.98 0.61
U 2 0975-04153232 17.0 15.7
G 1 N22011315637 17.1 15.7
49568 104.4103 6.9338 2452311 2 13.04 0.64
49568 104.4100 6.9337 2452312 1 12.82 0.54
U 9 0900-03903088 16.2 15.6
G 9 N22011221634 16.7 15.5
54083 106.5286 7.6204 2452252 2 12.89 0.79
U 7 0975-04597642 17.9 17.2
G 7 N223221317334 18.4 17.7
77974 116.4175 9.4440 2452319 16 12.62 0.80
77974 116.4178 9.4436 2452344 3 12.74 0.85
U 15 0975-05452565 17.2 15.1
G 3 N22122028318 13.3 12.8
Objects 11590, 40852 and 77974 may only be missing in
the USNO catalog.
Are there any suggestions for these stars ?
Below mag 13, the number of GSC "omissions" increases
enormously.
Patrick
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