Field list for NGC1647 magnitude charts 

Order#		Where a table is ordered by ascending visual magnitude, 
		the ordinal star number
Webda_id	The star number assigned by the Webda open cluster catalogue 
X		The X unit position assigned in the Webda open cluster catalogue 
Y		The Y unit position assigned in the Webda open cluster catalogue 
m_V		Visual magnitude (m_v), adjusted using Stanton 1999 equation to 
		translate Johnson ubv system V magnitudes to the visual system 
m_V_se		Standard error of m_v
RA_J2000	Right ascension 2000 epoch
Dec_J2000	Declination 
m_V_rnd		Rounded m_v - the value plotted on the magnitude chart
m_V_se_rnd	Rounded standard error of m_v
HD_id		Henry Draper star catalogue cross-reference id
Tycho_id	Tycho2 star catalogue cross-reference id 
Photometry_type	The source and type of the Johnson V used plot the object 
Johnson_V	For comparision purposes, the Johnson V used to compute m_v 
m_V_Diff	The difference between the computed visual magnitude and Johnson V magnitude
Spec		Spectral type 

Transformations applied: 

Johnson ubv V magnitude adjusted per Stanton 1999 equation 14:
m_v = V + 0.210(B-V)  

Tycho2 ubv V magnitude transformed to the Johnson ubv system: 
Per Note 7 to the Tycho-2 readme file for field V_T (Tycho photographic V magnitude) 
states -
    Blank when no magnitude is available. Either BTmag or VTmag is
    always given. Approximate Johnson photometry may be obtained as:
    V = VT - 0.09 * (BT - VT)

References: 

Photometry for NGC1647: 

Hog, E. et al. 2000.  The Tycho-2 Catalogue of the 2.5 million brightest stars. 
Astron. Astrophys. 366,L27 (photographic in Tycho ubv system)  

Turner, David G. 1992.  Galactic clusters with associated Cepheid variables III. 
NGC 1647 and SZ Tauri.  Astron.J. 104(5):1865  (photoelectric and photographic 
in Johnson ubv with average se of 0.03 for photoelectric and 0.01 for photographic) 

Francic, Stephen P. 1989.  Mass functions for eight nearby galactic clusters.  
Astron.J. 98(3):888 (photographic in Johnson ubv) 

Transformation of Johnson V magnitudes to visual magnitude system: 

Stanton, Richard H. 1999.  Visual magnitudes and the "average observer": 
The SS Cygni field experiment.  JAAVSO 27:97 (conversion equation to adjust 
Johnson ubv photometry to the visual system, i.e. - the human eye sees fainter 
for reddened stars than Johnson ubv filtered light)  

Transformation of Tycho2 V magnitudes to the Johnson ubv system: 

Bessell, M. July, 2000.  The Hipparcos and Tycho Photometric System Passbands.
PASP 112:961 

Supplemental worksheet supporting charts, in Excel 2000 format (763kb):
http://members.csolutions.net/fisherka/astronote/observed/NGC1647/NGC1647_XYZ_Chart_Plot.xls