[Aavso-photometry] GW Lib

[RICHARD MILES]

Tom et al.,

I managed absolute photometry on the field of GW Librae last night.

Reduction relative to HIP 74860 and HIP 74923 gives the following:

2007 Apr 19 01:47UT
V = 9.548 +/- 0.015
Ic = 9.595 +/-0.020
V-Ic = -0.05 +/- 0.02

Star TYC 6766 1577 yielded the following:
V = 9.222 +/- 0.014
Ic = 8.851 +/-0.015
V-Ic = +0.37 +/- 0.02

I also have a short time series to submit plus V- and I- photometry of 
selected chart stars down to V=13.  Just mention here that Stars 107 and 123 
on the chart AAVSO 020301 are very red with V-Ic colours of +1.78 and +2.00 
respectively and so are probably unsuitable for use as visual comparisons.

Hopefully Sonoita will have yielded an even better calibration of the field 
shortly and will shall be able to identify suitable visual comparison stars 
for use during the fade period.

Richard Miles
Golden Hill Obs., UK

----- Original Message ----- 
From: "Tom Richards" <tom at woodridgeobsy.org>
To: "AAVSO Photometry list" <aavso-photometry at mira.aavso.org>; 
<cba-chat at cba.phys.columbia.edu>
Sent: Thursday, April 19, 2007 11:36 AM
Subject: [Aavso-photometry] GW Lib all-nighter


> Just starting on GW Lib. Cloud map looks good for the night, but smoke is
> lowering transparency. 4 s in V and I.
>
>
>
> Tom Richards,
>
> Woodridge Observatory,  CBA Melbourne
>
> http://www.woodridgeobsy.org <http://www.woodridgeobsy.org/>
>
> Carpe noctem!
>
>
>
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