[vsnet-chat 1346] Re: Graham E-region standards

["William S G Walker" <astroman@voyager.co.nz>]

Brian and all,

Greetings. Some months ago I took note of the request for sequences for
visual observers in southern regions and mentioned that I'd try to get a
few, particularly of CVs. But it soon became clear that CCD photometry with
a 25cm SC telescope is rather different from UBV measures with a 50cm
offset german equatorial. In spite of that I've managed to do preliminary
work on several fields - UW Cen, S Aps, V803 Cen and NN Cen (for which the
image files were lost in error!).

The problem has been calibration of the CCD response and also obtaining
useful standards at an appropriate magnitude level. I was unaware of the
Graham work in the E Regions but this now provides a base which will not
saturate the pixels of an ST6 before the fainter stars can be measured! I
had planned to use the sequences around SN fields mentioned earlier but one
of the team at Auckland was reluctant to see this approach used. 

With the ST6 LX10 setup you don't have the luxury of a field eyepiece for
exact positioning and must rely on the finder. As well, the B response is
rather poor at 
magnitude 13 so we're using V-R to calibrate things. All of this takes a
little time to get used to hence the delays in production. But Bruce Sumner
and I are hoping to get a number of fields down to V = 16 in the not too
distant future. 

So what I'm saying is that some slow progress is being made. Within a few
months we hope to be producing a respectable number of results for visual
observers. And if anyone knows of anything useful a note would be
appreciated. Did Graham or anyone do a similar job on the F Regions?

Regards,
Stan


----------
> From: Brian Skiff <bas@lowell.edu>
> To: Jean-Claude.Mermilliod@obs.unige.ch;
aavso-discussion@physics.mcmaster.ca; barnes@lowell;
borde@dasgal1.obspm.fr; buie@lowell; buscombe@nwu.edu; csande@csc.com;
dubois@simbad.u-strasbg.fr; francois@simbad.u-strasbg.fr;
gerard@simbad.u-strasbg.fr; morel@ozemail.com.au; seu@pyxis.usno.navy.mil;
vsnet-chat@kusastro.kyoto-u.ac.jp; wayne.h.warren.1@gsfc.nasa.gov
> Subject: [vsnet-chat 1345] Graham E-region standards
> Date: Monday, September 28, 1998 8:29 PM
> 
> Star-catalogue folks,
>      I realized in the last few days that Graham's E-region standard
stars
> (1982PASP...94..244G) ware not available in machine-readable form from
the
> data centers.  I have compiled the data for the 102 stars, a sample of
which is
> is shown below, and give in addition accurate coordinates for the stars. 
The
> coordinates are not simply those of Graham precessed to equinox 2000, but
> obtained mostly from the GSC and USNO-A1.0 if they are not in some
astrometric
> catalogue.  Graham's positions turn out to have numerous errors and well
as
> being inaccurate because of the use of the Harvard Annals x,y coordinates
in
> their derivation.
>      Because they are very useful for analyzing and weighting photometric
> reductions, I have included the internal errors (mean errors of the mean)
and
> number of observations made by Graham.  Thus each line is about 113
columns
> wide.  The complete file (just 12Kb) is copied out to the Lowell ftp area
at:
> 
> http://ftp.lowell.edu/pub/bas/starcats/graham.stds
> 
> \Brian
> 
> 
> 
> Name              RA  (2000)  Dec        V      U-B    B-V    V-R    R-I 
 sigV   sigUB  sigBV  sigVR  sigRI   n
> [CS62] E1 41    1 24 41.9  -44 31 42    6.270  1.084  1.146  0.577  0.517
 0.003  0.006  0.002  0.001  0.004   5
> [CS62] E1 35    1 22 02.2  -44 25 30    9.471  1.679  1.427  0.777  0.722
 0.007  0.008  0.005  0.005  0.005   6
> [CS62] E1 20    1 23 16.4  -44 40 18    9.855  0.275  0.736  0.402  0.387
 0.008  0.009  0.008  0.004  0.005   5
> [CS62] E1 44    1 24 12.3  -44 27 01   10.885  0.146  0.620  0.359  0.334
 0.013  0.014  0.012  0.005  0.014   4
> [CS62] E1 49    1 24 57.6  -44 38 27   11.640  0.019  0.564  0.332  0.327
 0.017  0.009  0.013  0.010  0.014   4
> [CS62] E1 a     1 25 19.5  -44 27 02   12.666  0.020  0.615  0.341  0.335
 0.010  0.012  0.007  0.005  0.005   4
> [CS62] E1 h     1 24 40.0  -44 33 55   13.828  0.235  0.722  0.375  0.373
 0.010  0.010  0.011  0.011  0.014   4
> [CS62] E1 i     1 24 48.1  -44 38 31   13.759  0.614  0.916  0.514  0.446
 0.008  0.017  0.005  0.007  0.013   4
> [CS62] E1 p     1 24 04.6  -44 23 42   14.778  0.383  0.799  0.475  0.461
 0.009  0.017  0.006  0.006  0.012   4

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