256  QZ SERPENTIS   (UG:)   Range: 12.7-17.4V
     Position:   15 56 54.51  +21 07 19.4 (J2000, from .dat file)
     Magnitude:  V=17.491  B-V=0.561      (in .dat file)

ID     RA  (2000)   DEC       X    Y   N    V      ERR     B-V    ERR 

a) Comparison star sequence

1    15 57 47.2  +20 53 53   738 -806  2   9.992  0.000   0.540  0.002   
2    15 57 45.3  +20 58 05   711 -555  2  10.225  0.004   1.051  0.005   
3    15 57 40.2  +21 19 06   638  707  1  11.583  0.001   1.228  0.001   
4    15 57 02.6  +20 56 56   114 -623  3  12.130  0.017   1.028  0.011   
5    15 57 37.5  +21 08 53   602   94  1  12.612  0.001   1.018  0.001   
6    15 56 36.2  +21 14 04  -256  405  1  12.900  0.001   0.658  0.001   
7    15 56 46.0  +21 05 17  -118 -122  3  13.306  0.010   0.850  0.014   
8    15 57 06.6  +21 04 39   170 -161  3  13.594  0.011   0.561  0.013   
9    15 57 15.9  +21 09 17   299  118  3  14.093  0.006   1.321  0.007   
10   15 57 14.3  +20 57 48   278 -571  3  14.260  0.014   1.315  0.029   
11   15 57 00.2  +21 09 08    80  109  3  14.764  0.008   0.891  0.009   
12   15 56 57.0  +21 07 44    35   25  3  15.011  0.000   0.868  0.013   
13   15 56 45.6  +21 07 43  -125   24  3  15.424  0.006   0.784  0.015   
14   15 56 55.0  +21 07 12     7   -7  3  15.958  0.009   0.765  0.013   
15   15 56 52.8  +21 10 01   -23  162  3  16.327  0.006   0.825  0.017   
16   15 56 45.1  +21 07 12  -132   -7  3  16.916  0.021   1.387  0.014   
17   15 56 58.8  +21 05 26    60 -113  3  17.344  0.022   1.224  0.044   


b) Wide-colour extension for CCD calibration
     
     15 56 31.0  +21 12 19  -328  300  2  15.123  0.000   0.222  0.015   
     15 57 38.0  +21 10 05   608  166  1  14.541  0.003   1.394  0.007   


Notes:

1. The first three stars are saturated and their magnitudes and colours 
are approximate. However star #1 and #2 do have reliable Tycho-2 
magnitudes of V=10.07+/-0.04 and V=10.17+/-0.04 respectively.

2. There is another bright Tycho-2 star in the field at 15h 56m 26.3s 
+21d 14' 45" with V=7.98+/-0.01 and B-V=1.18.

3. There is a an additional bright variable star in the field, namely NSV
20457, located at 15h 57m 29.5s +20d 52' 19", with a range of 10.59-10.90
and unknown type.

4. Care will be needed when QZ Ser is in quiescence so as not to confuse 
it with its close neighbour, called #14 in this sequence. This companion 
is only 10 arcsec to the southeast of the variable with a magnitude of
V=16.0.

5. This variable was know previously as HadV4.

6. There are two galaxies in the field: anonymous V=17.0 galaxy at 
15h 56m 42.4s  +21d 08' 10" and MCG+04-18-601 at V=14.5 located at 
15h 56m 33.7s  +21d 17' 21". They both appears very much brighter on 
DSS images.


Bruce Sumner
5 March 2002
Revised 13 March 2002