[vsnet-chat 182] Re: V and v - comparisons

[Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>]

W S G Walker wrote:
> The question comes down to what you're trying to prove with the visual
> results. If a Mira star has an amplitude of five magnitudes then the
> usual +/- 0.1 to 0.5 of visual measures doesn't matter much. Epochs of
> maximum (or minimum) can be determined quite well from a dozen or so
> measures. The same with outbursts of dwarf novae, although here the
> subjectivity of visual observers comes in. DN seem to be measured too
> bright when compared with pe, RCrBs too faint. Wishful thinking or some
> real colour effect?

   In order to prove this, I have calculated personal deviations from
the averaged values taken from vsnet-obs observations.  Both stars have
well-established V sequences widely used.

Case 1) SS Cyg (1996 Aug. 23 - Sep. 9)

Code Mode  Corr   SD   Obs
 KSL      -0.01  0.10    3
 Oui      -0.38  0.03    5
 SQN       0.25  0.17   12
 LTO      -0.14  0.15    8
 FRF      -0.14  0.08    3
 Lin       0.08  0.10    5
 Nov       0.07  0.14    5
 DIE      -0.17  0.25    8
 JEN       0.03  0.24    4
 GRL      -0.04  0.16   13
 MIB       0.21  0.24    3
 BMM      -0.00  0.11    6
 VAN      -0.20  0.18    5
 Scp      -0.20  0.15   10
 PAE       0.22  0.15    6
 PIE      -0.12  0.16    7
 AFO       0.07  0.26    4
 TKV       0.02  0.11    6
 BMU       0.10  0.15   11
 POY      -0.32  0.21    4
 MKJ      -0.28  0.08    2
 Ths       0.09  0.08    2
 ZAG      -0.08  0.02    1
 SKP      -0.06  0.13    4
 DUM       0.03  0.17    2
 Mkn      -0.76  0.05    1
 Wnt      -0.09  0.05    1
 VIC       0.38  0.11    3
 Ymo       0.13  0.09    1
 Myy       0.40  0.08    2
 Nmt       0.09  0.07    1
 Kat       0.39  0.07    2
 SPO       0.05  0.47    3
 HSG       0.32  0.18    4
 SSU      -0.11  0.07    1
 Knk      -0.00  0.07    1
 BRO       0.21  0.19    3
 Oud    V -0.00  0.21    1
 MOE      -0.31  0.09    1

  Corr: minus values represent that observers estimate fainter than the
averaged light curve by all observers.  SD: root mean square of deviations
from the average.  Incidentally the only available V measurement agrees with
the visual average.  The scatter of each observer is an order of 0.1 - 0.2
mag.  I have no information which observer has experienced hypersensitization
with C2H5OH.

Case 2) AL Com  (1995 Apr. 6 - Apr. 30)

Code Mode  Corr   SD   Obs
 PIE       0.36  0.24    4
 POY       0.02  0.15   18
 Tny       0.08  0.10    1
 Ksm       0.24  0.12    3
 Ths       0.20  0.19    3
 Kis    V -0.10  0.04    3
 VAN      -0.02  0.17    5
 JEN      -0.11  0.16    6
 Arm      -0.62  0.17    4
 Wes       0.08  0.01    1
 Mkn      -0.07  0.20    2
 Wor      -0.03  0.04    1
 BRO       0.24  0.09    2

  The trend is very clear.  Most of visual observers estimated this star
brighter than V measures.  Unfiltered CCD magnitudes by Arm (M. Iida) gave
appreciably fainter values by 0.6 mag.

Regards,
Taichi Kato

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