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Photometric Catalogs



Landolt Photometric Standards
UBVRI Photometric Standard Stars
at -50 Degrees Declination

Accuracy of stellar positions

After spending more time checking the stellar positions against the UCAC2 data I have found that these Landolt stars are very close to the UCAC2 positions. In fact an error of 0.20 arcseconds or even less is common! Very good positional information EPOCH 2000. Someone has done their homework.

Distribution across TheSky

109 stars in file

Header used to define fields

>SEARCH 1,14
>RAHOURS 16,17
>RAMINUTES 19,20
>RASECONDS 22,27
>DECSIGN 29,29
>DECDEGREES 30,31 
>DECMINUTES 33,34
>DECSECONDS 36,40
>MAGNITUDE 42,47
>PARSE "Star Name" 1,14
>PARSE "(B-V) / (U-B) Color" 49,61
>PARSE "(V-R) / (R-I) Color" 63,75
>PARSE "(V-I) Color" 77,82
>PARSE "# observations / # nights" 84,88
>PARSE "Mean error V / B-V" 90,102
>PARSE "Mean error U-B / V-R" 104,116
>PARSE "Mean error R-I / V-I" 118,130
>IDENTIFIER Southern Landolt
>LOADMEMORY
>OBJECT TYPE 55 <------ENABLE OBJECT TYPE REFERENCE POINT CHANGE IF YOU LIKE!

Field Doubling up - Only 8 fields allowed

Because TheSky is currently limited to only 8 fields of information I had to double field to make all the fields visible. See below entry demonstrating this.

Object name: Southern Landolt: JL 163C
Magnitude: 14.4
Equatorial: RA: 00h 10m 59s Dec: -50°13'00"(current)
Equatorial 2000: RA: 00h 10m 38s Dec: -50°15'26"
Horizon: Azim: 155°10'46" Alt: -09°31'20"
Transit time: 12:16 Always below horizon.
Source catalog: Sky Database: Southern Landolt
DB field 1: Star Name: JL 163C
DB field 2: (B-V) / (U-B) Color: +0.828 +0.369    <--------------------------Fields doubled up
DB field 3: (V-R) / (R-I) Color: +0.458 +0.433    <--------------------------Fields doubled up
DB field 4: (V-I) Color: +0.892
DB field 5: # observations / # nights: 21 11      <--------------------------Fields doubled up
DB field 6: Mean error V / B-V: 0.0017 0.0046     <--------------------------Fields doubled up
DB field 7: Mean error U-B / V-R: 0.0096 0.0022   <--------------------------Fields doubled up
DB field 8: Mean error R-I / V-I: 0.0050 0.0061   <--------------------------Fields doubled up
Hour angle: -02h 41m 15s
Screen x,y: 723.00, 602.00
Sidereal time: 21:30
Click distance: 0.0000
Celestial type: 55
Index: 3
Catalog: 10

Searching the data

The SDB file can be searched using Edit | Find then Southern Landolt "STAR NAME" without the quotes. You can also expand the list and see all the individual entries under the heading Southern Landolt.  See below.

Find dialog

Type star name after Southern Landolt
or go down the list!

If you don't like the name I have chosen for the SDB you can recompile the data with any name you like or object type. I chose object type REFERENCE POINT not STARS so these would stand out. However, you can change the object type and SDB name at the point of recompiling. You don't have to edit the header text but should for consistency if you make changes.

Labeling the stars

To label the stars you need to pick the fields you want to label. View | Display Explorer then Expand the SDB by name and select the fields. You must also enable the EXTENDED labels. That is View | Labels | Extended Labels must be checked.

View | Display Explorer

Pick fields here

Screen showing labeled stars

Name and B-V / U-B
Red markers are the Landolt stars
white UCAC2

ReadME
Title: UBVRI Photometric Standard Stars Around the Sky 
       at -50 Degrees Declination 
Author: Landolt A.U. 
Table: UBVRI Photometry of Standard Stars Near -50 Degrees Declination
================================================================================
Byte-by-byte Description of file: datafile1.txt
--------------------------------------------------------------------------------
   Bytes Format Units    Label  Explanations
--------------------------------------------------------------------------------
   1- 14 A14    ---      Name   Star name
  16- 17 I2     h        RAh    Hour of Right Ascension (J2000) 
  19- 20 I2     min      RAm    Minute of Right Ascension (J2000) 
  22- 27 F6.3   s        RAs    Second of Right Ascension (J2000) 
      29 A1     ---      DE-    Sign of the Declination (J2000)
  30- 31 I2     deg      DEd    Degree of Declination (J2000) 
  33- 34 I2     arcmin   DEm    Arcminute of Declination (J2000) 
  36- 40 F5.2   arcsec   DEs    Arcsecond of Declination (J2000) 
  42- 47 F6.3   mag      Vmag   The V band magnitude 
  49- 54 F6.3   mag      B-V    The (B-V) color
  56- 61 F6.3   mag      U-B    The (U-B) color
  63- 68 F6.3   mag      V-R    The (V-R) color
  70- 75 F6.3   mag      R-I    The (R-I) color
  77- 82 F6.3   mag      V-I    The (V-I) color
  84- 85 I2     ---      Num    Number of times the star was observed
  87- 88 I2     ---      Night  Number of nights the star was observed
  90- 95 F6.4   mag    e_Vmag   Mean error in Vmag 
  97-102 F6.4   mag    e_B-V    Mean error in B-V 
 104-109 F6.4   mag    e_U-B    Mean error in U-B 
 111-116 F6.4   mag    e_V-R    Mean error in V-R 
 118-123 F6.4   mag    e_R-I    Mean error in R-I 
 125-130 F6.4   mag    e_V-I    Mean error in V-I 
--------------------------------------------------------------------------------